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1

Seebeck effect in magnetic tunnel junctions.  

PubMed

Creating temperature gradients in magnetic nanostructures has resulted in a new research direction, that is, the combination of magneto- and thermoelectric effects. Here, we demonstrate the observation of one important effect of this class: the magneto-Seebeck effect. It is observed when a magnetic configuration changes the charge-based Seebeck coefficient. In particular, the Seebeck coefficient changes during the transition from a parallel to an antiparallel magnetic configuration in a tunnel junction. In this respect, it is the analogue to the tunnelling magnetoresistance. The Seebeck coefficients in parallel and antiparallel configurations are of the order of the voltages known from the charge-Seebeck effect. The size and sign of the effect can be controlled by the composition of the electrodes' atomic layers adjacent to the barrier and the temperature. The geometric centre of the electronic density of states relative to the Fermi level determines the size of the Seebeck effect. Experimentally, we realized 8.8% magneto-Seebeck effect, which results from a voltage change of about -8.7 ?V K?¹ from the antiparallel to the parallel direction close to the predicted value of -12.1 ?V K?¹. In contrast to the spin-Seebeck effect, it can be measured as a voltage change directly without conversion of a spin current. PMID:21785418

Walter, Marvin; Walowski, Jakob; Zbarsky, Vladyslav; Münzenberg, Markus; Schäfers, Markus; Ebke, Daniel; Reiss, Günter; Thomas, Andy; Peretzki, Patrick; Seibt, Michael; Moodera, Jagadeesh S; Czerner, Michael; Bachmann, Michael; Heiliger, Christian

2011-10-01

2

Theory of the spin Seebeck effect.  

PubMed

The spin Seebeck effect refers to the generation of a spin voltage caused by a temperature gradient in a ferromagnet, which enables the thermal injection of spin currents from the ferromagnet into an attached nonmagnetic metal over a macroscopic scale of several millimeters. The inverse spin Hall effect converts the injected spin current into a transverse charge voltage, thereby producing electromotive force as in the conventional charge Seebeck device. Recent theoretical and experimental efforts have shown that the magnon and phonon degrees of freedom play crucial roles in the spin Seebeck effect. In this paper, we present the theoretical basis for understanding the spin Seebeck effect and briefly discuss other thermal spin effects. PMID:23420561

Adachi, Hiroto; Uchida, Ken-ichi; Saitoh, Eiji; Maekawa, Sadamichi

2013-03-01

3

Seebeck effect at the atomic scale.  

PubMed

The atomic variations of electronic wave functions at the surface and electron scattering near a defect have been detected unprecedentedly by tracing thermoelectric voltages given a temperature bias [Cho et al., Nat. Mater. 12, 913 (2013)]. Because thermoelectricity, or the Seebeck effect, is associated with heat-induced electron diffusion, how the thermoelectric signal is related to the atomic-scale wave functions and what the role of the temperature is at such a length scale remain very unclear. Here we show that coherent electron and heat transport through a pointlike contact produces an atomic Seebeck effect, which is described by the mesoscopic Seebeck coefficient multiplied by an effective temperature drop at the interface. The mesoscopic Seebeck coefficient is approximately proportional to the logarithmic energy derivative of local density of states at the Fermi energy. We deduced that the effective temperature drop at the tip-sample junction could vary at a subangstrom scale depending on atom-to-atom interaction at the interface. A computer-based simulation method of thermoelectric images is proposed, and a point defect in graphene was identified by comparing experiment and the simulation of thermoelectric imaging. PMID:24745445

Lee, Eui-Sup; Cho, Sanghee; Lyeo, Ho-Ki; Kim, Yong-Hyun

2014-04-01

4

Seebeck Effect at the Atomic Scale  

NASA Astrophysics Data System (ADS)

The atomic variations of electronic wave functions at the surface and electron scattering near a defect have been detected unprecedentedly by tracing thermoelectric voltages given a temperature bias [Cho et al., Nat. Mater. 12, 913 (2013)]. Because thermoelectricity, or the Seebeck effect, is associated with heat-induced electron diffusion, how the thermoelectric signal is related to the atomic-scale wave functions and what the role of the temperature is at such a length scale remain very unclear. Here we show that coherent electron and heat transport through a pointlike contact produces an atomic Seebeck effect, which is described by the mesoscopic Seebeck coefficient multiplied by an effective temperature drop at the interface. The mesoscopic Seebeck coefficient is approximately proportional to the logarithmic energy derivative of local density of states at the Fermi energy. We deduced that the effective temperature drop at the tip-sample junction could vary at a subangstrom scale depending on atom-to-atom interaction at the interface. A computer-based simulation method of thermoelectric images is proposed, and a point defect in graphene was identified by comparing experiment and the simulation of thermoelectric imaging.

Lee, Eui-Sup; Cho, Sanghee; Lyeo, Ho-Ki; Kim, Yong-Hyun

2014-04-01

5

Magnons, Spin Current and Spin Seebeck Effect  

NASA Astrophysics Data System (ADS)

When metals and semiconductors are placed in a temperature gradient, the electric voltage is generated. This mechanism to convert heat into electricity, the so-called Seebeck effect, has attracted much attention recently as the mechanism for utilizing wasted heat energy. [1]. Ferromagnetic insulators are good conductors of spin current, i.e., the flow of electron spins [2]. When they are placed in a temperature gradient, generated are magnons, spin current and the spin voltage [3], i.e., spin accumulation. Once the spin voltage is converted into the electric voltage by inverse spin Hall effect in attached metal films such as Pt, the electric voltage is obtained from heat energy [4-5]. This is called the spin Seebeck effect. Here, we present the linear-response theory of spin Seebeck effect based on the fluctuation-dissipation theorem [6-8] and discuss a variety of the devices. [4pt] [1] S. Maekawa et al, Physics of Transition Metal Oxides (Springer, 2004). [0pt] [2] S. Maekawa: Nature Materials 8, 777 (2009). [0pt] [3] Concept in Spin Electronics, eds. S. Maekawa (Oxford University Press, 2006). [0pt] [4] K. Uchida et al., Nature 455, 778 (2008). [0pt] [5] K. Uchida et al., Nature Materials 9, 894 (2010) [0pt] [6] H. Adachi et al., APL 97, 252506 (2010) and Phys. Rev. B 83, 094410 (2011). [0pt] [7] J. Ohe et al., Phys. Rev. B (2011) [0pt] [8] K. Uchida et al., Appl. Phys. Lett. 97, 104419 (2010).

Maekawa, Sadamichi

2012-02-01

6

Intrinsic Spin Seebeck Effect in Gold  

NASA Astrophysics Data System (ADS)

In Spin Seebeck Effect (SSE), a pure spin current can be generated by a temperature gradient (?T) and detected by the inverse spin Hall effect usually by Pt. Due to the propensity of out-of-plane ?zT through substrate, the SSE in the transverse configuration with an in-plane ?xT has been shown contaminated by the anomalous Nernst effect.footnotetextS. Y. Huang, et al. Phys. Rev. Lett. 107, 216604 (2011) The SSE in the longitudinal configuration with ?zT suffers from the magnetic proximity effect (MPE) of Pt in contact with a ferromagnetic material thus also contaminated.footnotetextS. Y. Huang, et al. Phys. Rev. Lett. 109, 107204 (2012) In this work, we demonstrate that Au does not exhibit MPE and reveals the intrinsic SSE. In contrast to Pt/YIG, Au/YIG shows no anomalous Hall signals, very weak inverse MR, and non-monotonic thickness dependence of spin thermal voltage, thus very weak if any MPE. Our results place an upper limit to the intrinsic SSE of 0.1?V/K at the Au thickness of 8nm, two orders of magnitude smaller than that in Pt/YIG. Spin-polarized density-functional calculations also show a sizable Pt but a negligible Au magnetic moment in contact with YIG, in agreement with experiments.

Qu, Danru; Huang, Ssu-Yen; Hu, Jun; Wu, Ruqian; Chien, Chia-Ling

2013-03-01

7

Theory of phonon-driven spin Seebeck effect  

NASA Astrophysics Data System (ADS)

Spin Seebeck effect refers to a thermal spin injection occurring over millimeter scales from a ferromagnet into an attached nonmagnetic metal [Uchida et al., Nature 455, 778 (2008)]. We discuss the importance of the phonon-drag process in the spin Seebeck effect. Our theory of phonon-drag spin Seebeck effect [Adachi et al., Appl. Phys. Lett. 97, 252506 (2010)] explains simultaneously the local nature of the spin Seebeck effect [Jaworski et al., Nature Materials 9, 898 (2010); Uchida et al., Nature Materials 10, 737 (2011)] and the signal enhancement at low temperatures [Jaworski et al., Phys. Rev. Lett. 106, 186601 (2011)]. We also discuss the difference between our approach and that developed in Xiao et al., Phys. Rev. B 81, 214418 (2010).

Adachi, Hiroto; Ohe, Jun-Ichiro; Takahashi, Saburo; Maekawa, Sadamichi

2012-02-01

8

Giant spin Seebeck effect in a non-magnetic material.  

PubMed

The spin Seebeck effect is observed when a thermal gradient applied to a spin-polarized material leads to a spatially varying transverse spin current in an adjacent non-spin-polarized material, where it gets converted into a measurable voltage. It has been previously observed with a magnitude of microvolts per kelvin in magnetically ordered materials, ferromagnetic metals, semiconductors and insulators. Here we describe a signal in a non-magnetic semiconductor (InSb) that has the hallmarks of being produced by the spin Seebeck effect, but is three orders of magnitude larger (millivolts per kelvin). We refer to the phenomenon that produces it as the giant spin Seebeck effect. Quantizing magnetic fields spin-polarize conduction electrons in semiconductors by means of Zeeman splitting, which spin-orbit coupling amplifies by a factor of ?25 in InSb. We propose that the giant spin Seebeck effect is mediated by phonon-electron drag, which changes the electrons' momentum and directly modifies the spin-splitting energy through spin-orbit interactions. Owing to the simultaneously strong phonon-electron drag and spin-orbit coupling in InSb, the magnitude of the giant spin Seebeck voltage is comparable to the largest known classical thermopower values. PMID:22785317

Jaworski, C M; Myers, R C; Johnston-Halperin, E; Heremans, J P

2012-07-12

9

Intrinsic Spin Seebeck Effect in Au/YIG  

NASA Astrophysics Data System (ADS)

The acute magnetic proximity effects in Pt/YIG compromise the suitability of Pt as a spin current detector. We show that Au/YIG, with no anomalous Hall effect and a negligible magnetoresistance, allows the measurements of the intrinsic spin Seebeck effect with a magnitude much smaller than that in Pt/YIG. The experiment results are consistent with the spin polarized density functional calculations for Pt with a sizable and Au with a negligible magnetic moment near the interface with YIG.

Qu, D.; Huang, S. Y.; Hu, Jun; Wu, Ruqian; Chien, C. L.

2013-02-01

10

Intrinsic spin Seebeck effect in Au/YIG.  

PubMed

The acute magnetic proximity effects in Pt/YIG compromise the suitability of Pt as a spin current detector. We show that Au/YIG, with no anomalous Hall effect and a negligible magnetoresistance, allows the measurements of the intrinsic spin Seebeck effect with a magnitude much smaller than that in Pt/YIG. The experiment results are consistent with the spin polarized density functional calculations for Pt with a sizable and Au with a negligible magnetic moment near the interface with YIG. PMID:23432301

Qu, D; Huang, S Y; Hu, Jun; Wu, Ruqian; Chien, C L

2013-02-01

11

Enhanced thermoelectric performance and anomalous seebeck effects in topological insulators.  

PubMed

Improving the thermoelectric figure of merit zT is one of the greatest challenges in material science. The recent discovery of topological insulators (TIs) offers new promise in this prospect. In this work, we demonstrate theoretically that zT is strongly size dependent in TIs, and the size parameter can be tuned to enhance zT to be significantly greater than 1. Furthermore, we show that the lifetime of the edge states in TIs is strongly energy dependent, leading to large and anomalous Seebeck effects with an opposite sign to the Hall effect. These striking properties make TIs a promising material for thermoelectric science and technology. PMID:24949782

Xu, Yong; Gan, Zhongxue; Zhang, Shou-Cheng

2014-06-01

12

Enhanced Thermoelectric Performance and Anomalous Seebeck Effects in Topological Insulators  

NASA Astrophysics Data System (ADS)

Improving the thermoelectric figure of merit zT is one of the greatest challenges in material science. The recent discovery of topological insulators (TIs) offers new promise in this prospect. In this work, we demonstrate theoretically that zT is strongly size dependent in TIs, and the size parameter can be tuned to enhance zT to be significantly greater than 1. Furthermore, we show that the lifetime of the edge states in TIs is strongly energy dependent, leading to large and anomalous Seebeck effects with an opposite sign to the Hall effect. These striking properties make TIs a promising material for thermoelectric science and technology.

Xu, Yong; Gan, Zhongxue; Zhang, Shou-Cheng

2014-06-01

13

Skyrmionic spin Seebeck effect via dissipative thermomagnonic torques  

NASA Astrophysics Data System (ADS)

We derive thermomagnonic torque and its "?-type" dissipative correction from the stochastic Landau-Lifshitz-Gilbert equation. The ?-type dissipative correction describes viscous coupling between magnetic dynamics and magnonic current and it stems from spin mistracking of the magnetic order. We show that thermomagnonic torque is important for describing temperature gradient induced motion of skyrmions in helical magnets while dissipative correction plays an essential role in generating transverse Magnus force. We propose to detect such skyrmionic motion by employing the transverse spin Seebeck effect geometry.

Kovalev, Alexey A.

2014-06-01

14

Designing a study of the Spin Seebeck Effect  

NASA Astrophysics Data System (ADS)

The Spin Seebeck Effect (SSE) refers to the recently discovered generation of a spin voltage as a result of an applied temperature gradient. The SSE has been observed in ferromagnetic (FM) metals, semiconductors, and insulators. This area of research has attracted much interest because it may provide a means to make use of waste heat from electronic devices. While several theories have been presented, there are still open questions regarding the physical mechanism of this effect. Recent experimental evidence suggests that magnons and phonons play a role in thermal spin physics; however, the experiments done to date are performed primarily through detection of a voltage via the Inverse Spin Hall Effect that is due to the steady-state accumulation of a spin distribution across the FM material and consequently provide only indirect information on the magnons. Here we will discuss an experimental setup that we have designed to explore the role of magnons in the SSE using Brillouin light scattering.

Riley, Grant; Liu, Jason; Roberts, Gerri; Buchanan, Kristen

2012-10-01

15

Seebeck effect in PbTe films and EuTe/PbTe superlattices  

NASA Astrophysics Data System (ADS)

Theoretical calculations of the Seebeck coefficients of bulk PbTe and PbTe based superlattices were described in the framework of Boltzmann equation, taking into account temperature dependent band gaps, nonparabolicity, and anisotropy of effective masses. It is shown that the temperature gradient along the superlattice layer works more effectively on the enhancement of the thermoelectric figure of merit than the temperature gradient normal to the superlattice layer. Calculated Seebeck coefficients were compared to the experimental values for n-type PbTe, p-type PbTe, and EuTe/PbTe superlattices. The Seebeck coefficient of p-type PbTe was higher than that of n-type PbTe. The relatively high Seebeck coefficient is explained by the contribution from other extrema in the valence band. The EuTe/PbTe [001] superlattice shows higher Seebeck coefficients than PbTe bulk owing to the large density of states.

Ishida, Akihiro; Yamada, Tomohiro; Cao, Daoshe; Inoue, Yoku; Veis, Martin; Kita, Takuji

2009-07-01

16

Seebeck effects in a graphene nanoribbon coupled to two ferromagnetic leads  

NASA Astrophysics Data System (ADS)

We theoretically investigate the Seebeck effects for the system of a narrow graphene nanoribbon between two ferromagnetic (FM) electrodes with noncollinear magnetic moments. Both zigzag-edge graphene nanoribbons (ZGNRs) and armchair-edge graphene nanoribbons (AGNRs) have been considered. By using the nonequilibrium Green's function method combining with the tight-binding Hamiltonian, it is demonstrated that, the Seebeck coefficients are sensitive to the chirality and width of the nanoribbon in the absence of magnetic field. Compared with 22-ZGNR and metallic 17-AGNR systems, semiconducting 15-AGNR system is found to posses superior thermoelectric performance, its Seebeck coefficients can be improved by two orders of magnitude. Meanwhile, the Seebeck coefficients for both 22-ZGNR and metallic 17-AGNR systems are the same order as that of graphene system. Furthermore, the Seebeck coefficients are strongly dependent on the magnetization M as well as magnetic configuration of the two FM leads. Particularly, the Seebeck coefficient drastically enhances when the magnetization of the two FM leads is in antiparallel configuration. Interestingly, the Seebeck coefficient for both 22-ZGNR and metallic 17-AGNR systems increases with increasing temperature T, while it decreases with increasing T for semiconducting 15-AGNR system. Moreover, the dependence Seebeck coefficients on magnetic flux ? show an oscillation behavior. The results obtained here may provide a valuable theoretical guidance to experimentally design heat spintronic devices.

Zhou, Benhu; Zhou, Benliang; Zeng, Yangsu; Zhou, Guanghui; Ouyang, Tao

2014-03-01

17

Longitudinal spin Seebeck effect in various garnet ferrites  

NASA Astrophysics Data System (ADS)

The longitudinal spin Seebeck effect (LSSE) is investigated in various garnet ferrites Y3-xRxFe5-yMyO12 (R=Gd, Ca; M=Al, Mn, V, In, Zr) by means of the inverse spin Hall effect in Pt films. The magnitude of the LSSE voltage in the Pt/Y3-xRxFe5-yMyO12 samples is found to be enhanced with increasing concentration of Fe in the garnet ferrites, which can be explained by a change in the spin-mixing conductance at the Pt/Y3-xRxFe5-yMyO12 interfaces. We also investigate the dependence of the LSSE voltage on macroscopic magnetic parameters of Y3-xRxFe5-yMyO12. The experimental results show that the LSSE voltage in the Pt/Y3-xRxFe5-yMyO12 samples has a positive correlation with the Curie temperature and the saturation magnetization, but no clear correlation with the gyromagnetic ratio and the Gilbert damping constant of the samples.

Uchida, K.; Nonaka, T.; Kikkawa, T.; Kajiwara, Y.; Saitoh, E.

2013-03-01

18

Magneto-Seebeck effect and thermal torques in magnetic tunnel junctions  

NASA Astrophysics Data System (ADS)

Creating temperature gradients in magnetic nanostructures has resulted in a new research direction, i.e., the combination of magneto- and thermoelectric effects. Magnetic tunnel devices, known for application as magnetic sensor in hard disc drives or magnetic random access memories (MRAM) show large magnetoresistance. We show that in nanoscale magnetic tunnel junctions, the Seebeck voltage in a heat gradient can be controlled via the magnetization. The Seebeck coefficient changes during the transition from a parallel to an antiparallel magnetic configuration in a tunnel junction -- the magneto-Seebeck effect. In that respect, it is the analog to the tunneling magnetoresistance and thus is called tunneling magneto-Seebeck effect (or tunneling magnetothermopower). The change in Seebeck coefficients is in the order of the voltages known from the charge-Seebeck effect in semiconductors (up to 100 ?V/K). Their size and sign can be delicately controlled by the composition of the electrodes' atomic layers adjacent to the barrier and the temperature and we observe a characteristic sign change from positive to negative magneto-Seebeck effects as theoretically predicted. It is known that generally strong electronic asymmetry at around the Fermi level results in a large Seebeck effect. Here the magnetization dependence of the charge-Seebeck coefficients varying up to >100% for the parallel and the antiparallel originates from the half-metallic like transmission of the tunnel junction. Using heating with ultrafast laser pulses, these thermal gradients can be of up to 20 K across the tunnel barrier. We demonstrate that we can achieve the parameters predicted, where by thermal torques magnetization switching is expected. This allows to conceptually think of MRAM's driven by heat gradients only. [4pt] [1] M. Walter, et al. Nature Mater. 10, 742 (2011).

Muenzenberg, Markus

2012-02-01

19

Spin-resolved Fano resonances induced large spin Seebeck effects in graphene-carbon-chain junctions  

NASA Astrophysics Data System (ADS)

We propose a high-efficiency thermospin device constructed by a carbon atomic chain sandwiched between two ferromagnetic (FM) zigzag graphene nanoribbon electrodes. In the low-temperature regime, the magnitude of the spin figure of merit is nearly equal to that of the corresponding charge figure of merit. This is attributed to the appearances of spin-resolved Fano resonances in the linear conductance spectrum resulting from the quantum interference effects between the localized states and the expanded states. The spin-dependent Seebeck effect is obviously enhanced near these Fano resonances with the same spin index; meanwhile, the Seebeck effect of the other spin component has a smaller value due to the smooth changing of the linear conductance with the spin index. Thus, a large spin Seebeck effect is achieved, and the magnitude of the spin figure of merit can reach 1.2 at T = 25 K. Our results indicate that the FM graphene-carbon-chain junctions can be used to design the high-efficiency thermospin devices.

Liu, Yu-Shen; Zhang, Xue; Feng, Jin-Fu; Wang, Xue-Feng

2014-06-01

20

Observation of the spin-Seebeck effect in a ferromagnetic semiconductor.  

PubMed

Reducing the heat generated in traditional electronics is a chief motivation for the development of spin-based electronics, called spintronics. Spin-based transistors that do not strictly rely on the raising or lowering of electrostatic barriers can overcome scaling limits in charge-based transistors. Spin transport in semiconductors might also lead to dissipation-less information transfer with pure spin currents. Despite these thermodynamic advantages, little experimental literature exists on the thermal aspects of spin transport in solids. A recent and surprising exception was the discovery of the spin-Seebeck effect, reported as a measurement of a redistribution of spins along the length of a sample of permalloy (NiFe) induced by a temperature gradient. This macroscopic spatial distribution of spins is, surprisingly, many orders of magnitude larger than the spin diffusion length, which has generated strong interest in the thermal aspects of spin transport. Here, the spin-Seebeck effect is observed in a ferromagnetic semiconductor, GaMnAs, which allows flexible design of the magnetization directions, a larger spin polarization, and measurements across the magnetic phase transition. This effect is observed even in the absence of longitudinal charge transport. The spatial distribution of spin currents is maintained across electrical breaks, highlighting the local nature of this thermally driven effect. PMID:20871608

Jaworski, C M; Yang, J; Mack, S; Awschalom, D D; Heremans, J P; Myers, R C

2010-11-01

21

Spin-dependent Seebeck effect in non-local spin valve devices  

NASA Astrophysics Data System (ADS)

We performed measurements of Py/Cu and Py/Ag lateral spin valves as a function of injection current direction and magnitude. Above a ``critical'' current, there is an unexpected dependence of spin injection on current direction. Positive currents show higher polarization of spin injection than negative. This implies that in addition to current-induced spin injection, there is a thermally induced injection from a spin-dependent Seebeck effect. A temperature gradient in the Py electrode, caused by Joule heating, is responsible for injecting excess spins into the non-magnetic channel. This effect has important consequences for understanding high-current spin-based devices, such as spin transfer torque devices.

Erekhinsky, Mikhail; Casanova, Fèlix; Schuller, Ivan K.; Sharoni, Amos

2012-05-01

22

Investigation of the magnetic properties of insulating thin films using the longitudinal spin Seebeck effect  

NASA Astrophysics Data System (ADS)

The longitudinal spin Seebeck effect is used as a detector for the magnetic properties and switching characteristics of magnetic thin insulating films. We use a 300 nm and a 20 nm thick Yttrium Iron Garnet (YIG, Y3Fe5O12) film prepared by pulsed laser deposition and afterwards coated by platinum for the detection of the thermally excited magnons by the inverse spin Hall effect. The inverse spin Hall signals reveal a magnetic uniaxial anisotropy along the direction of the platinum stripe in the thicker film. For the thin film we find a more isotropic behavior, which is complementarily observed using the magnetoresistance occurring at the platinum/YIG interface. We explain our results on the basis of x-ray diffraction data, which reveal a miscut of the substrate and film surface and an expansion of the YIG lattice. Both findings favor a growth-induced magnetic anisotropy that we observe.

Kehlberger, A.; Jakob, G.; Onbasli, M. C.; Kim, D. H.; Ross, C. A.; Kläui, M.

2014-05-01

23

Time dependence of CO2 laser pulses recorded in the mixed detector regime of the photon drag and Seebeck effects in n-doped GaAs  

Microsoft Academic Search

In this paper, we present experimental work on the temporal profiling of transversly excited atmosphere (TEA) CO2 laser pulses by using a particular kind of semiconductor photodetector. The detector exploits the combined effects of two fast sensing mechanisms, namely, the electron temperature related Seebeck and photon drag effects, and one slow mechanism, the phonon related Seebeck effect. The design of

V. Kotov; J. Stiens; G. Shkerdin; W. Vandermeiren; G. Borghs; R. Vounckx

2007-01-01

24

Fokker-Planck approach to the theory of the magnon-driven spin Seebeck effect  

NASA Astrophysics Data System (ADS)

Following the theoretical approach by J. Xiao [Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.81.214418 81, 214418 (2010)] to the spin Seebeck effect, we calculate the mean value of the total spin current flowing through a normal metal/ferromagnet interface. The spin current emitted from the ferromagnet to the normal metal is evaluated in the framework of the Fokker-Planck approach for the stochastic Landau-Lifshitz-Gilbert equation. We show that the total spin current depends not only on the temperature difference between the electron and the magnon baths, but also on the external magnetic field and magnetic anisotropy. Apart from this, the spin current is shown to saturate with increasing magnon temperature, and the saturation temperature increases with increasing magnetic field and/or magnetic anisotropy.

Chotorlishvili, L.; Toklikishvili, Z.; Dugaev, V. K.; Barna?, J.; Trimper, S.; Berakdar, J.

2013-10-01

25

Spectral non-uniform temperature and non-local heat transfer in the spin Seebeck effect.  

PubMed

Recently discovered spin-dependent thermoelectric effects have merged spin, charge, and thermal physics, known as spin caloritronics, of which the spin Seebeck effect is its most puzzling. Here we present a theory of this effect driven by subthermal non-local phonon heat transfer and spectral non-uniform temperature. The theory explains its non-local behaviour from the fact that phonons that store the energy (thermal) and the phonons that transfer it (subthermal) are located in different parts of the spectrum and have different kinetics. This gives rise to a spectral phonon distribution that deviates from local equilibrium along the substrate and is sensitive to boundary conditions. The theory also predicts a non-magnon origin of the effect in ferromagnetic metals in agreement with observations in recent experiments. Equilibration of the heat flow from the substrate to the Pt probe and backwards leads to a vertical spin current produced by the spin-polarized electrons dragged by the thermal phonons. PMID:23735931

Tikhonov, Konstantin S; Sinova, Jairo; Finkel'stein, Alexander M

2013-01-01

26

Robust longitudinal spin-Seebeck effect in Bi-YIG thin films.  

PubMed

In recent years, the coupling of magnetic insulators (bismuth-doped yttrium iron garnet, Bi-YIG) with platinum has garnered significant interest in spintronics research due to applicability as spin-current-driven thermoelectric coatings. These coatings bridge the gap between spintronics technologies and thermoelectric materials, providing a novel means of transforming waste heat into electricity. However, there remain questions regarding the origins of the spin-Seebeck effect (SSE) as well as claims that observed effects are a manifestation of magnetic proximity effects, which would induce magnetic behavior in platinum. Herewith we provide support that the voltages observed in the Bi-YIG/Pt films are purely SSE voltages. We reaffirm claims that magnon transport theory provides an ample basis for explaining SSE behavior. Finally, we illustrate the advantages of pulsed-laser deposition, as these Bi-YIG films possess large SSE voltages (even in absence of an external magnetic field), as much as twice those of films fabricated via solution-based methods. PMID:24651124

Siegel, Gene; Prestgard, Megan Campbell; Teng, Shiang; Tiwari, Ashutosh

2014-01-01

27

Robust longitudinal spin-Seebeck effect in Bi-YIG thin films  

PubMed Central

In recent years, the coupling of magnetic insulators (bismuth-doped yttrium iron garnet, Bi-YIG) with platinum has garnered significant interest in spintronics research due to applicability as spin-current-driven thermoelectric coatings. These coatings bridge the gap between spintronics technologies and thermoelectric materials, providing a novel means of transforming waste heat into electricity. However, there remain questions regarding the origins of the spin-Seebeck effect (SSE) as well as claims that observed effects are a manifestation of magnetic proximity effects, which would induce magnetic behavior in platinum. Herewith we provide support that the voltages observed in the Bi-YIG/Pt films are purely SSE voltages. We reaffirm claims that magnon transport theory provides an ample basis for explaining SSE behavior. Finally, we illustrate the advantages of pulsed-laser deposition, as these Bi-YIG films possess large SSE voltages (even in absence of an external magnetic field), as much as twice those of films fabricated via solution-based methods.

Siegel, Gene; Prestgard, Megan Campbell; Teng, Shiang; Tiwari, Ashutosh

2014-01-01

28

Magnetotransport properties and Seebeck effect in the superconductor FeSe0.5Te0.5  

NASA Astrophysics Data System (ADS)

We carried out measurements of the electrical resistivity, magnetoresistance, Hall resistivity and Seebeck effect in a highly oriented sample of the Fe-based FeSe0.5Te0.5 superconductor. Complementary structural and magnetic characterizations were also performed. Our sample do not show long-range magnetic order down to 4.2 K. Superconductivity occurs with critical temperature Tc ? 15 K. In the normal phase, the resistivity versus temperature behavior mimics that of a Kondo-lattice system. The magnetoresistance, Hall coefficient and Seebeck coefficient show sign reversals. These results are discussed with basis on the combined effects from two-band conduction and weak magnetic fluctuations. Effects from superconducting fluctuations are also observed near Tc.

Pimentel, J. L., Jr.; Pureur, P.; Avila, M. A.; Ribeiro, R. A.

2014-04-01

29

A novel strongly correlated electronic thin-film laser energy/power meter based on anisotropic Seebeck effect  

NASA Astrophysics Data System (ADS)

Strongly correlated electronic (SCE) materials including high-temperature superconducting cuprate and colossal magnetoresistance manganite thin films demonstrate tremendous anisotropic Seebeck effect which makes them very promising for developing high-performance laser detectors. In this work, laser-induced thermoelectric voltage (LITV) signals with nanosecond response time have been measured in SCE La1-x Pb x MnO3 thin films based on anisotropic Seebeck effect at room temperature. The magnitude of the LITV signals increases linearly with laser energy/power density in a wide range of laser wavelengths from ultraviolet, visible to infrared based on which a novel SCE thin-film laser energy/power meter has been developed.

Zhang, G.-Y.; Zhang, H.; Tan, S.-L.; Zhang, P.-X.; Tseng, T.-Y.; Habermeier, H.-U.; Lin, C.-T.; Singjai, P.

2014-03-01

30

The Thermal Conductivity and Seebeck Effect of Impure Indium Antimonide in a Magnetic Field.  

National Technical Information Service (NTIS)

A study was made of the thermal conductivity and Seebeck coefficient of a single crystal of InSb containing 3.3(10) to the 18th power tellurium atoms per cubic cm. Measurements were made in the temperature range of 338K to 648K and at magnetic fields betw...

E. F. Ault

1964-01-01

31

High Seebeck effects from conducting polymer: Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) based thin-film device with hybrid metal/polymer/metal architecture  

NASA Astrophysics Data System (ADS)

Conductive polymers are of particular interest for thermoelectric applications due to their low thermal conductivity and relatively high electrical conductivity. In this study, commercially available conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) was used in a hybrid metal/polymer/metal thin film design in order to achieve a high Seebeck coefficient with the value of 252 ?V/k on a relatively low temperature scale. Polymer film thickness was varied in order to investigate its influence on the Seebeck effect. The high Seebeck coefficient indicates that the metal/polymer/metal design can develop a large entropy difference in internal energy of charge carriers between high and low-temperature metal electrodes to develop electrical potential due to charge transport in conducting polymer film through metal/polymer interface. Therefore, the metal/polymer/metal structure presents a new design to combine inorganic metals and organic polymers in thin-film form to develop Seebeck devices.

Stanford, Michael; Wang, Hsin; Ivanov, Ilia; Hu, Bin

2012-10-01

32

High temperature Seebeck coefficient metrology  

SciTech Connect

We present an overview of the challenges and practices of thermoelectric metrology on bulk materials at high temperature (300 to 1300 K). The Seebeck coefficient, when combined with thermal and electrical conductivity, is an essential property measurement for evaluating the potential performance of novel thermoelectric materials. However, there is some question as to which measurement technique(s) provides the most accurate determination of the Seebeck coefficient at high temperature. This has led to the implementation of nonideal practices that have further complicated the confirmation of reported high ZT materials. To ensure meaningful interlaboratory comparison of data, thermoelectric measurements must be reliable, accurate, and consistent. This article will summarize and compare the relevant measurement techniques and apparatus designs required to effectively manage uncertainty, while also providing a reference resource of previous advances in high temperature thermoelectric metrology.

Martin, J. [Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Tritt, T. [Department of Physics and Astronomy, Clemson University, Clemson, South Carolina 29634 (United States); Uher, C. [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109 (United States)

2010-12-15

33

Time-resolved measurement of the tunnel magneto-Seebeck effect in a single magnetic tunnel junction.  

PubMed

Recently, several groups have reported spin-dependent thermoelectric effects in magnetic tunnel junctions. In this paper, we present a setup for time-resolved measurements of thermovoltages and thermocurrents of a single micro- to nanometer-scaled tunnel junction. An electrically modulated diode laser is used to create a temperature gradient across the tunnel junction layer stack. This laser modulation technique enables the recording of time-dependent thermovoltage signals with a temporal resolution only limited by the preamplifier for the thermovoltage. So far, time-dependent thermovoltage could not be interpreted. Now, with the setup presented in this paper, it is possible to distinguish different Seebeck voltage contributions to the overall measured voltage signal in the ?s time regime. A model circuit is developed that explains those voltage contributions on different sample types. Further, it will be shown that a voltage signal arising from the magnetic tunnel junction can only be observed when the laser spot is directly centered on top of the magnetic tunnel junction, which allows a lateral separation of the effects. PMID:23822355

Boehnke, Alexander; Walter, Marvin; Roschewsky, Niklas; Eggebrecht, Tim; Drewello, Volker; Rott, Karsten; Münzenberg, Markus; Thomas, Andy; Reiss, Günter

2013-06-01

34

Coupled polaron-phonon effects on Seebeck coefficient and lattice conductivity of B13C2 from first principles  

NASA Astrophysics Data System (ADS)

The anomalous temperature-independent behavior of the Seebeck coefficient and the lattice thermal conductivity of B13C2 are explained through polaron and phonon evolutions found using ab initio molecular dynamics (AIMD). Analyses of lattice dynamics show that the unique icosahedron structures dominate the optical phonon modes and CBC intericosahedral bonds dominate the local acoustic vibration. We identify that the temperature-induced Jahn-Teller distortion and electron-phonon coupling in icosahedron structures create small polarons (i.e., charge trapping and phonon softening). We also verify that large-displacement chain atoms scatter heat-conducting phonons. Using equilibrium and nonequilibrium AIMD methods (including entropy and energy analyses), we predict the Seebeck coefficient and its components as well as the lattice thermal conductivity, and we find good agreement with experiments. Softened and localized phonons make a significant vibrational contribution to the Seebeck coefficient and allow for an amorphous-like lattice thermal conductivity.

Kim, Hyoungchul; Kaviany, Massoud

2013-04-01

35

Tunable Seebeck Coefficient in Monolayer Graphene Under Periodic Potentials  

NASA Astrophysics Data System (ADS)

The effect of the superlattice potential on the Seebeck coefficient tensor of graphene sheet is theoretically investigated. Strong anisotropy of the Seebeck coefficient tensor is observed. The origin of the anisotropy can be attributed to the modification of the dispersion relation in the vicinity of the Dirac point. Our finding shows that the magnitude of the Seebeck coefficient of graphene can be flexibly changed under a superlattice potential.

Ono, Shota; Zhang, Ming; Noda, Yusuke; Ohno, Kaoru

2014-06-01

36

ac Current Generation in Chiral Magnetic Insulators and Skyrmion Motion induced by the Spin Seebeck Effect  

NASA Astrophysics Data System (ADS)

We show that a temperature gradient induces an ac electric current in multiferroic insulators when the sample is embedded in a circuit. We also show that a thermal gradient can be used to move magnetic Skyrmions in insulating chiral magnets: the induced magnon flow from the hot to the cold region drives the Skyrmions in the opposite direction via a magnonic spin transfer torque. Both results are combined to compute the effect of Skyrmion motion on the ac current generation and demonstrate that Skyrmions in insulators are a promising route for spin caloritronics applications.

Lin, Shi-Zeng; Batista, Cristian D.; Reichhardt, Charles; Saxena, Avadh

2014-05-01

37

ac Current Generation in Chiral Magnetic Insulators and Skyrmion Motion induced by the Spin Seebeck Effect.  

PubMed

We show that a temperature gradient induces an ac electric current in multiferroic insulators when the sample is embedded in a circuit. We also show that a thermal gradient can be used to move magnetic Skyrmions in insulating chiral magnets: the induced magnon flow from the hot to the cold region drives the Skyrmions in the opposite direction via a magnonic spin transfer torque. Both results are combined to compute the effect of Skyrmion motion on the ac current generation and demonstrate that Skyrmions in insulators are a promising route for spin caloritronics applications. PMID:24856718

Lin, Shi-Zeng; Batista, Cristian D; Reichhardt, Charles; Saxena, Avadh

2014-05-01

38

Huge Seebeck coefficients in nonaqueous electrolytes  

NASA Astrophysics Data System (ADS)

The Seebeck coefficients of the nonaqueous electrolytes tetrabutylammonium nitrate, tetraoctylphosphonium bromide, and tetradodecylammonium nitrate in 1-octanol, 1-dodecanol, and ethylene-glycol are measured in a temperature range from T = 30 °C to T = 45 °C. The Seebeck coefficient is generally of the order of a few hundreds of microvolts per Kelvin for aqueous solution of inorganic ions. Here we report huge values of 7 mV/K at 0.1 M concentration for tetrabutylammonium nitrate in 1-dodecanol. These striking results open the question of unexpectedly large kosmotrope or ``structure making'' effects of tetraalkylammonium ions on the structure of alcohols.

Bonetti, M.; Nakamae, S.; Roger, M.; Guenoun, P.

2011-03-01

39

Nanoscale Spin Seebeck Rectifier: Controlling Thermal Spin Transport across Insulating Magnetic Junctions with Localized Spin  

NASA Astrophysics Data System (ADS)

The spin Seebeck effect is studied across a charge insulating magnetic junction, in which thermal-spin conjugate transport is assisted by the exchange interactions between the localized spin in the center and electrons in metallic leads. We show that, in contrast with bulk spin Seebeck effect, the figure of merit of such nanoscale thermal-spin conversion can be infinite, leading to the ideal Carnot efficiency in the linear response regime. We also find that in the nonlinear spin Seebeck transport regime the device possesses the asymmetric and negative differential spin Seebeck effects. In the last, the situations with leaking electron tunneling are also discussed. This nanoscale thermal spin rectifier, by tuning the junction parameters, can act as a spin Seebeck diode, spin Seebeck transistor, and spin Seebeck switch, which could have substantial implications for flexible thermal and information control in molecular spin caloritronics.

Ren, Jie; Fransson, Jonas; Zhu, Jian-Xin

2014-06-01

40

Separation of longitudinal spin Seebeck effect from anomalous Nernst effect: Determination of origin of transverse thermoelectric voltage in metal/insulator junctions  

NASA Astrophysics Data System (ADS)

The longitudinal spin Seebeck effect (LSSE) and the anomalous Nernst effect (ANE) are investigated in various metal/insulator junction systems and a clear separation of the LSSE from the ANE induced by static magnetic proximity is demonstrated. This separation is realized by comparing transverse thermoelectric voltage in in-plane magnetized (IM) and perpendicularly magnetized (PM) configurations, where the LSSE appears only in the IM configuration while the ANE appears both in the IM and PM configurations. We show that, in Pt/Y3Fe5O12 samples, the LSSE voltage in the IM configuration is three orders of magnitude greater than the proximity-ANE contamination estimated from the data in the PM configuration. This quantitative voltage comparison between the IM and PM configurations is corroborated by systematic voltage measurements in Ni81Fe19/Gd3Ga5O12, Pt/Gd3Ga5O12, Au/Y3Fe5O12, and Au/Gd3Ga5O12 samples and by our phenomenological model calculation. The LSSE measurements in high magnetic field regions further confirm that the observed voltage in the Pt/Y3Fe5O12 and Au/Y3Fe5O12 samples is of magnon origin. We apply this voltage comparison method also to a Ni81Fe19/Y3Fe5O12 sample and show that both the LSSE and ANE exist in this sample.

Kikkawa, T.; Uchida, K.; Daimon, S.; Shiomi, Y.; Adachi, H.; Qiu, Z.; Hou, D.; Jin, X.-F.; Maekawa, S.; Saitoh, E.

2013-12-01

41

Seebeck coefficient measurements of lithium isotopes  

NASA Astrophysics Data System (ADS)

Lithium, owing to its many advantages, is of immense interest to the fusion community for its use as plasma facing component (PFC) material. Various experiments are under progress in the Center for Plasma Material Interactions (CPMI) at the University of Illinois at Urbana Champaign (UIUC) aimed at understanding the plasma-lithium interactions. In one such experiment called Solid/Liquid Lithium Divertor Experiment (SLiDE), it was recently observed that the flow of liquid lithium in the presence of magnetic fields is dominated by thermoelectric Magnetohydrodynamic (TEMHD) effects. To describe these results accurately, a knowledge of the thermoelectric properties of lithium is essential. For this purpose, an apparatus to measure the Seebeck coefficient of lithium was developed. Using this apparatus, the Seebeck coefficient of lithium as a function of temperature has been obtained. The Seebeck coefficient of lithium-7 is found to gradually increase from 11 ?V/K to 25 ?V/K, as the temperature is raised from 25 °C to 240 °C. These measurements are in good agreement with Kendall's thermoelectric measurements on natural Li. Furthermore, using the same apparatus, the thermoelectric curve of lithium-6 is obtained and for the first time are reported in this paper.

Surla, V.; Tung, M.; Xu, W.; Andruczyk, D.; Neumann, M.; Ruzic, D. N.; Mansfield, D.

2011-08-01

42

Spin-Seebeck effect on the surface of a topological insulator due to nonequilibrium spin-polarization parallel to the direction of thermally driven electronic transport  

NASA Astrophysics Data System (ADS)

We study the transverse spin-Seebeck effect (SSE) on the surface of a three-dimensional topological insulator (TI) thin film, such as Bi2Se3, which is sandwiched between two normal metal leads. The temperature bias ?T applied between the leads generates surface charge current which becomes spin polarized due to strong spin-orbit coupling on the TI surface, with polarization vector acquiring a component Px?60% parallel to the direction of transport. When the third nonmagnetic voltage probe is attached to the portion of the TI surface across its width Ly, pure spin current will be injected into the probe where the inverse spin Hall effect (ISHE) converts it into a voltage signal |VISHE|max/?T ?2.5?V/K (assuming the SH angle of the Pt voltage probe and Ly=1 mm). The existence of predicted nonequilibrium spin polarization parallel to the direction of electronic transport and the corresponding electron-driven SSE crucially relies on orienting quintuple layers (QLs) of Bi2Se3 orthogonal to the TI surface and tilted by 45? with respect to the direction of transport. Our analysis is based on the Landauer-Büttiker-type formula for spin currents in the leads of a multiterminal quantum-coherent junction, which is constructed by using nonequilibrium Green function formalism within which we show how to take into account arbitrary orientation of QLs via the self-energy describing coupling between semi-infinite normal metal leads and the TI sample.

Chang, Po-Hao; Mahfouzi, Farzad; Nagaosa, Naoto; Nikoli?, Branislav K.

2014-05-01

43

The effects of increased Co-ion spin states on the Seebeck coefficient in thermoelectric Ca3Co4O9  

NASA Astrophysics Data System (ADS)

Thermoelectric oxides have attracted increasing attention due to their high thermal power and temperature stability. In particular, Ca3Co4O9 (CCO), a misfit layered structure consisting of single layer hole-doped CoO2 sandwiched between insulating Ca2CoO3 rocksalt layers, exhibits a high Seebeck coefficient at 1,000 K. It was previously suggested that the Seebeck-coefficient can be further improved by stabilizing an increased Co-ion spin state in the CoO2 layers. Here we report a significant increase in the room-temperature in-plane Seebeck coefficient of 40 nm thick CCO films grown by pulsed laser deposition on SrTiO3 substrates. We combine aberration-corrected Z-contrast imaging, atomic-column resolved electron energy-loss spectroscopy, and density-functional calculations to show that the increase is caused by CoO2 stacking faults with Co^4+-ions in a higher spin state compared to that of bulk CCO. The higher Seebeck coefficient makes the CCO system suitable for many high-temperature waste-heat-recovery applications. The role of dopants, such as Bi and Ti will also be explored.

Klie, Robert; Paulauskas, Tadas; Qiao, Qiao; Rebola, Alejandro; Ogut, Serdar; Mazumdar, Dipanjan; Gupta, Arun; Kolesnik, Stanislaw; Idrobo, Juan-Carlos

2012-02-01

44

Apparatus for the high temperature measurement of the Seebeck coefficient in thermoelectric materials.  

PubMed

The Seebeck coefficient is a physical parameter routinely measured to identify the potential thermoelectric performance of a material. However, researchers employ a variety of techniques, conditions, and probe arrangements to measure the Seebeck coefficient, resulting in conflicting materials data. To compare and evaluate these methodologies, and to identify optimal Seebeck coefficient measurement protocols, we have developed an improved experimental apparatus to measure the Seebeck coefficient under multiple conditions and probe arrangements (300 K-1200 K). This paper will describe in detail the apparatus design and instrumentation, including a discussion of its capabilities and accuracy as measured through representative diagnostics. In addition, this paper will emphasize the techniques required to effectively manage uncertainty in high temperature Seebeck coefficient measurements. PMID:22755656

Martin, Joshua

2012-06-01

45

Thermal spin current and magnetothermopower by Seebeck spin tunneling  

NASA Astrophysics Data System (ADS)

The recently observed Seebeck spin tunneling, the thermoelectric analog of spin-polarized tunneling, is described. The fundamental origin is the spin dependence of the Seebeck coefficient of a tunnel junction with at least one ferromagnetic electrode. Seebeck spin tunneling creates a thermal flow of spin-angular momentum across a tunnel barrier without a charge tunnel current. In ferromagnet/insulator/semiconductor tunnel junctions, this can be used to induce a spin accumulation ?? in the semiconductor in response to a temperature difference ?T between the electrodes. A phenomenological framework is presented to describe the thermal spin transport in terms of parameters that can be obtained from experiment or theory. Key ingredients are a spin-polarized thermoelectric tunnel conductance and a tunnel spin polarization with nonzero energy derivative, resulting in different Seebeck tunnel coefficients Sst? and Sst? for majority and minority spin electrons. We evaluate the thermal spin current, the induced spin accumulation and ??/?T, discuss limiting regimes, and compare thermal and electrical flow of spin across a tunnel barrier. A salient feature is that the thermally induced spin accumulation is maximal for smaller tunnel resistance, in contrast to the electrically induced spin accumulation that suffers from the impedance mismatch between a ferromagnetic metal and a semiconductor. The thermally induced spin accumulation produces an additional thermovoltage proportional to ??, which can significantly enhance the conventional charge thermopower. Owing to the Hanle effect, the thermopower can also be manipulated with a magnetic field, producing a Hanle magnetothermopower.

Jansen, R.; Deac, A. M.; Saito, H.; Yuasa, S.

2012-03-01

46

Spin-dependent Seebeck coefficients of Ni80Fe20 and Co in nanopillar spin valves  

NASA Astrophysics Data System (ADS)

We have experimentally determined the spin-dependent Seebeck coefficient of permalloy (Ni80Fe20) and cobalt (Co) using nanopillar spin valve devices, a stack of two ferromagnetic layers separated by a nonmagnetic layer. The devices were specifically designed to separate heat-related effects from charge-related effects. A heat current, with no accompanying charge current, through the nanopillar spin valve leads to a thermovoltage proportional to the spin-dependent Seebeck coefficient SS=S?-S? of the ferromagnet, where S? and S? are the Seebeck coefficient for spin-up and spin-down electrons. By using a three-dimensional finite-element model based on spin-dependent thermoelectric theory, whose input material parameters were measured in separate devices, we were able to accurately determine a spin-dependent Seebeck coefficient of -1.8 ?V K-1 and -4.5 ?V K-1 for cobalt and permalloy, respectively, corresponding to a Seebeck coefficient polarization PS=SS/SF of 0.08 and 0.25, where SF is the Seebeck coefficient of the ferromagnet. The results are in agreement with earlier theoretical work in Co/Cu multilayers and spin-dependent Seebeck and spin-dependent Peltier measurements in Ni80Fe20/Cu spin valve structures.

Dejene, F. K.; Flipse, J.; van Wees, B. J.

2012-07-01

47

Seebeck Coefficient of Semiconducting Oxide Glasses.  

National Technical Information Service (NTIS)

The Seebeck Coefficient, alpha, of semiconducting glasses based on vanadium pentoxide can be calculated from a knowledge of the concentration ratio of the high and low valence ions. The concentration of vanadium ions in the glass and long range order appa...

T. Allersma J. D. Mackenzie

1966-01-01

48

First-Principles Estimation of Seebeck Coefficient of Bismuth Telluride and Selenide  

NASA Astrophysics Data System (ADS)

The first-principles electronic band structure calculation has been used to examine the relationship between the Bi/Sb composition ratio and the Seebeck coefficient in (Bi1-xSbx)2Te3. The Te/Se ratio dependence in Bi2(Te1-xSex)3 has also been investigated and the results have been compared. Because spin--orbit interaction affects the band structure to a large extent, its inclusion is crucial to a quantitative discussion on the Seebeck coefficient. We have found that the Bi/Sb or Te/Se ratio does not have a large effect on the Seebeck coefficient. However, carrier density largely influences the temperature dependence of the Seebeck coefficient. Both the p- and n-type of thermoelectric materials were examined and the results show that their stabilities have the same tendency. The carrier densities in them are largely associated with defects, which suggests that a careful defect control is very important in the production process.

Yamamoto, Masahiro; Hamada, Noriaki

2012-12-01

49

System to Measure Thermal Conductivity and Seebeck Coefficient for Thermoelectrics  

NASA Technical Reports Server (NTRS)

The Seebeck coefficient, when combined with thermal and electrical conductivity, is an essential property measurement for evaluating the potential performance of novel thermoelectric materials. However, there is some question as to which measurement technique(s) provides the most accurate determination of the Seebeck coefficient at elevated temperatures. This has led to the implementation of nonstandardized practices that have further complicated the confirmation of reported high ZT materials. The major objective of the procedure described is for the simultaneous measurement of the Seebeck coefficient and thermal diffusivity within a given temperature range. These thermoelectric measurements must be precise, accurate, and reproducible to ensure meaningful interlaboratory comparison of data. The custom-built thermal characterization system described in this NASA-TM is specifically designed to measure the inplane thermal diffusivity, and the Seebeck coefficient for materials in the ranging from 73 K through 373 K.

Kim, Hyun-Jung; Skuza, Jonathan R.; Park, Yeonjoon; King, Glen C.; Choi, Sang H.; Nagavalli, Anita

2012-01-01

50

Magnetic-doped alloys with very large Seebeck coefficients  

NASA Technical Reports Server (NTRS)

Preliminary results of this study show that, based on selection of magnetic solute and nonmagnetic solvent from periodic table, alloys having Seebeck coefficients approaching 100 micron V/K can be obtained.

Sellmeyer, D. J.; Zagarins, J.

1972-01-01

51

The impact of commonly used approximations on the computation of the Seebeck coefficient and mobility of polar semiconductors  

NASA Astrophysics Data System (ADS)

Seebeck coefficient modeling and measurement has important applications in direct thermal to electrical energy conversion and solid-state physics. The computations of the Seebeck coefficient and mobility of polar semiconductors in the literature often employ certain approximations, notably the relaxation time approximation (RTA) and the truncation of the Boltzmann transport equation. We study the accuracy of these approximations as a function of the effective mass, temperature, and carrier concentration using a recently developed technique for rigorous solution of the Boltzmann transport equation. We find that the approximations give rise to considerable error in the computed Seebeck coefficients of heavily doped semiconductors with a low effective mass, and that the RTA is entirely inapplicable for the accurate computation of the mobility of several important materials.

Ramu, Ashok T.; Bowers, John E.

2012-10-01

52

Fast Seebeck coefficient measurement based on dynamic method  

NASA Astrophysics Data System (ADS)

A setup based on dynamic method was developed for fast Seebeck coefficient measurement from room temperature to 473 K. Two T-type thermocouples with a response time of less than 0.1 s were used to measure the dynamic temperatures of the sample. The Cu wires of the two thermocouples served as leads for Seebeck voltage measurement. The dynamic temperature feature of the setup was characterized. Test measurements were conducted with LaCo0.9Cu0.1O3 and LaCo0.85Cu0.15O3 samples with the customized setup, and the results had a difference of ±8.4% compared with the data provided by ZEM-2 (Ulvac-Riko, Japan), which showed that the Seebeck measurement with the customized setup was reliable. In addition, the error on the Seebeck coefficient caused by the dynamic variation of temperature was discussed. The setup described in this paper has the advantage of fast Seebeck coefficient measurement with a measurement speed of about 14-23 K min-1.

Zhou, Yang; Yang, Donghua; Li, Liangliang; Li, Fu; Li, Jing-Feng

2014-05-01

53

Quantifying the local Seebeck coefficient with scanning thermoelectric microscopy  

NASA Astrophysics Data System (ADS)

We quantify the local Seebeck coefficient with scanning thermoelectric microscopy, using a direct approach to convert temperature gradient-induced voltages (V) to Seebeck coefficients (S). We use a quasi-3D conversion matrix that considers both the sample geometry and the temperature profile. For a GaAs p-n junction, the resulting S-profile is consistent with that computed using the free carrier concentration profile. This combined computational-experimental approach is expected to enable nanoscale measurements of S across a wide variety of heterostructure interfaces.

Walrath, J. C.; Lin, Y. H.; Pipe, K. P.; Goldman, R. S.

2013-11-01

54

A high temperature apparatus for measurement of the Seebeck coefficient  

SciTech Connect

A high temperature Seebeck coefficient measurement apparatus with various features to minimize typical sources of error is designed and built. Common sources of temperature and voltage measurement error are described and principles to overcome these are proposed. With these guiding principles, a high temperature Seebeck measurement apparatus with a uniaxial 4-point contact geometry is designed to operate from room temperature to over 1200 K. This instrument design is simple to operate, and suitable for bulk samples with a broad range of physical types and shapes.

Iwanaga, Shiho; Toberer, Eric S.; LaLonde, Aaron; Snyder, G. Jeffrey [Materials Science, California Institute of Technology, Pasadena, California 91125 (United States)

2011-06-15

55

First principles explanation of the positive seebeck coefficient of lithium.  

PubMed

Lithium is one of the simplest metals, with negative charge carriers and a close reproduction of free-electron dispersion. Experimentally, however, Li is one of a handful of elemental solids (along with Cu, Ag, and Au) where the sign of the Seebeck coefficient (S) is opposite to that of the carrier. This counterintuitive behavior still lacks a satisfactory interpretation. We calculate S fully from first principles, within the framework of Allen's formulation of Boltzmann transport theory. Here it is crucial to avoid the constant relaxation time approximation, which gives a sign for S which is necessarily that of the carriers. Our calculated S are in excellent agreement with experimental data, up to the melting point. In comparison with another alkali metal, Na, we demonstrate that within the simplest nontrivial model for the energy dependency of the electron lifetimes, the rapidly increasing density of states (DOS) across the Fermi energy is related to the sign of S in Li. The exceptional energy dependence of the DOS is beyond the free-electron model, as the dispersion is distorted by the Brillouin zone edge; this has a stronger effect in Li than other alkali metals. The electron lifetime dependency on energy is central, but the details of the electron-phonon interaction are found to be less important, contrary to what has been believed for several decades. Band engineering combined with the mechanism exposed here may open the door to new "ambipolar" thermoelectric materials, with a tunable sign for the thermopower even if either n- or p-type doping is impossible. PMID:24877957

Xu, Bin; Verstraete, Matthieu J

2014-05-16

56

First Principles Explanation of the Positive Seebeck Coefficient of Lithium  

NASA Astrophysics Data System (ADS)

Lithium is one of the simplest metals, with negative charge carriers and a close reproduction of free-electron dispersion. Experimentally, however, Li is one of a handful of elemental solids (along with Cu, Ag, and Au) where the sign of the Seebeck coefficient (S) is opposite to that of the carrier. This counterintuitive behavior still lacks a satisfactory interpretation. We calculate S fully from first principles, within the framework of Allen's formulation of Boltzmann transport theory. Here it is crucial to avoid the constant relaxation time approximation, which gives a sign for S which is necessarily that of the carriers. Our calculated S are in excellent agreement with experimental data, up to the melting point. In comparison with another alkali metal, Na, we demonstrate that within the simplest nontrivial model for the energy dependency of the electron lifetimes, the rapidly increasing density of states (DOS) across the Fermi energy is related to the sign of S in Li. The exceptional energy dependence of the DOS is beyond the free-electron model, as the dispersion is distorted by the Brillouin zone edge; this has a stronger effect in Li than other alkali metals. The electron lifetime dependency on energy is central, but the details of the electron-phonon interaction are found to be less important, contrary to what has been believed for several decades. Band engineering combined with the mechanism exposed here may open the door to new "ambipolar" thermoelectric materials, with a tunable sign for the thermopower even if either n- or p-type doping is impossible.

Xu, Bin; Verstraete, Matthieu J.

2014-05-01

57

Seebeck Coefficient of Lithium and Lithium-Tin Alloys  

NASA Astrophysics Data System (ADS)

Experiments into the viability of lithium as a first wall material in a fusion device have shown that it offers great benefits in reducing recycling of hydrogenic species at the wall, increasing energy confinement times, and gettering impurities. However, concerns have been raised about its practicality in regions of high heat fluxes, and one of the greatest is whether or not a lithium divertor concept can function at high steady state temperatures without significant evaporation of the lithium. Lithium-tin alloys might offer a solution by suppressing evaporation, but their performance in a TEMHD driven device such as the LIMIT device under development at UIUC is directly dependent on their thermoelectric properties, namely their unknown Seebeck coefficient. In support of the use of lithium-tin alloys in such a device, experiments are performed to recover the Seebeck coefficient of several different compositions of lithium-tin alloys. Experiments previously performed at the University of Illinois of the Seebeck coefficient of lithium [1] were confirmed and expanded upon by this study. Values of ranging from 12 +/-1 uV/K at 82C to 28 +/-1 uV/K at 240C were obtained.[4pt] [1] V. Surla et al. Journal of Nuclear Materials 415 (2011) 18-22.

Kirsch, L.; Fiflis, P.; Andruczyk, D.; Curreli, D.; Ruzic, D. N.

2012-10-01

58

Seebeck coefficient of Bi-Sb samples grown by mechanical alloying  

Microsoft Academic Search

We report Seebeck coefficient, S(T) and electrical resistivity, ?(T) measurements of Bi0.88Sb0.12 compounds prepared by mechanical alloying (MA). The behavior of the Seebeck coefficient and electrical resistivity were studied as a function of temperature and the milling time (MT). The milling process was carried out at room temperature and took different values from 0 hours to 45 hours. The Seebeck

J. E. Rodriguez; D. Cadavid

2005-01-01

59

An instrument for the high temperature measurement of the Seebeck coefficient and electrical resistivity  

NASA Astrophysics Data System (ADS)

A system for the simultaneous measurement of thermoelectric power and resistivity of one and/or two samples over a temperature range of 300–1000 K in a vacuum chamber is designed and implemented. A sample probe is developed to provide its easy mounting and usage. In addition, two samples can be measured at the same time. Measurement accuracy has been enhanced by beadless thermocouples and micro-heaters that are specifically designed in order to minimize the ‘cold-finger effect’ and to eliminate some possible source of contact, design and measurement errors. A broad range of physical types and shapes of samples, such as bulk, bar or disc, can be measured by a software controlled system. A differential steady-state method has been applied for Seebeck coefficient measurement. Resistivity measurement is conducted with the axial technique of the four-point probe method. Platinum wire and a niobium rod are chosen as the standard samples. The total data error for the Seebeck coefficient and resistivity measurements is estimated to be less than 2.6% and 1%, respectively.

Gunes, Murat; Parlak, Mehmet; Ozenbas, Macit

2014-05-01

60

Thermocyclic stability of candidate Seebeck coefficient standard reference materials at high temperature  

NASA Astrophysics Data System (ADS)

The Seebeck coefficient is the most widely measured property specific to thermoelectric materials. There is currently no consensus on measurement protocols, and researchers employ a variety of techniques to measure the Seebeck coefficient. The implementation of standardized measurement protocols and the use of reliable Seebeck Coefficient Standard Reference Materials (SRMs®) will allow the accurate interlaboratory comparison and validation of materials data, thereby accelerating the development and commercialization of more efficient thermoelectric materials and devices. To enable members of the thermoelectric materials community the means to calibrate Seebeck coefficient measurement equipment, NIST certified SRM® 3451 "Low Temperature Seebeck Coefficient Standard (10 K to 390 K)". Due to different practical requirements in instrumentation, sample contact methodology, and thermal stability, a complementary SRM® is required for the high temperature regime (300 K to 900 K). The principal requirement of a SRM® for the Seebeck coefficient at high temperature is thermocyclic stability. We therefore characterized the thermocyclic behavior of the Seebeck coefficient for a series of candidate materials: constantan, p-type single crystal SiGe, and p-type polycrystalline SiGe, by measuring the temperature dependence of the Seebeck coefficient as a function of 10 sequential thermal cycles, between 300 K and 900 K. We employed multiple regression analysis to interpolate and analyze the thermocyclic variability in the measurement curves.

Martin, Joshua; Wong-Ng, Winnie; Caillat, Thierry; Yonenaga, I.; Green, Martin L.

2014-05-01

61

Seebeck rectification enabled by intrinsic thermoelectrical coupling in magnetic tunneling junctions.  

PubMed

An intrinsic thermoelectric coupling effect in the linear response regime of magnetic tunneling junctions (MTJ) is reported. In the dc response, it leads to a nonlinear correction to Ohm's law. Dynamically, it enables a novel Seebeck rectification and second harmonic generation, which apply for a broad frequency range and can be magnetically controlled. A phenomenological model on the footing of the Onsager reciprocal relation and the principle of energy conservation explains very well the experimental results obtained from both dc and frequency-dependent transport measurements performed up to GHz frequencies. Our work refines previous understanding of magnetotransport and microwave rectification in MTJs. It forms a new foundation for utilizing spin caloritronics in high-frequency applications. PMID:22861893

Zhang, Z H; Gui, Y S; Fu, L; Fan, X L; Cao, J W; Xue, D S; Freitas, P P; Houssameddine, D; Hemour, S; Wu, K; Hu, C-M

2012-07-20

62

Enhancement of Spin-Seebeck Voltage by Spin-Hall Thermopile  

NASA Astrophysics Data System (ADS)

Voltage signals induced by the spin-Seebeck effect (SSE) are shown to be enhanced by introducing a thermopile structure consisting of two different metals with positive and negative spin-Hall angles. In the ``spin-Hall thermopile'', the positive and negative SSE signals in the metals are added to the output voltage in series. Here, we demonstrate that a Pt/Nb thermopile on an Y3Fe5O12 (YIG) slab exhibits the SSE voltage one order of magnitude greater than that in a plain Pt/YIG system. Since the spin-Hall thermopile enables sensitive detection of a spin voltage in a versatile manner, it will be useful to construct spin and heat sensors.

Uchida, Ken-ichi; Nonaka, Tatsumi; Yoshino, Tatsuro; Kikkawa, Takashi; Kikuchi, Daisuke; Saitoh, Eiji

2012-09-01

63

Studies on Seebeck Coefficient of Individual Bismuth Telluride Nanotube  

NASA Astrophysics Data System (ADS)

We have studied on Seebeck coefficient (S) of freestanding individual Bismuth Telluride nanotubes using micro-fabricated thermoelectric workbench at the temperatures from 300 K to 25 K. The thermoelectric workbench is composed of three main elements: heater, thermocouple, and platinum pad. A polysilicon-gold thermocouple accurately measures the temperature, arising from the heat generated at the tips of the test sites from the polysilicon heater located 2 ?m apart from the thermocouple. Platinum pads placed on top of the heater and thermocouple structures and electrically isolated from these constitute S measurement circuit. IPA solution containing Bi2Te3 nanotubes was drop-cast on the workbench and the Ebeam Induced Deposition of platinum was used to improve the electrical and thermal contacts between nanotube and platinum pads. The inner and outer diameter of nanotube is 50 nm and 70 nm, respectively. The sign of obtained S was positive which is indicating the nanotube is p-type. And the magnitude was increased compared to the bulk and nanowire types. The measured S (364 ?V/K) of nanotube at T = 300 K is 1.65 times larger than that (220 ?V/K) of bulk and 1.4 times larger than the previously reported value (260 ?V/K) of nanowire.

Kim, Duksoo; Du, Renzhong; Yin, Yuewei; Dong, Sining; Li, Xiaoguang; Li, Qi; Tadigadapa, Srinivas

2013-03-01

64

Multifunctional probes for high-throughput measurement of Seebeck coefficient and electrical conductivity at room temperature  

NASA Astrophysics Data System (ADS)

An apparatus capable of rapid measurement of the Seebeck coefficient and electrical resistivity at room temperature is reported. The novel aspect of this apparatus is the use of 4 multifunctional probes that comprise a junction of two conductors at the tip and serve as both thermocouples and electrical contacts. In addition, one of the probes has a built-in heater that can establish a temperature gradient in the sample for the Seebeck measurement. The technique does not require special sample geometries or preparation of contacts and is suitable for bulk and thin film materials. Together with automated sample stage and data acquisition, the equipment is able to measure both the Seebeck coefficient and electrical resistivity in less than 20 s with good accuracy. Less than 5% and 4% relative errors were found for the measurement of the Seebeck coefficient and electrical resistivity, respectively. This makes the apparatus especially useful for high throughput evaluation of thermoelectric materials.

García-Cañadas, Jorge; Min, Gao

2014-04-01

65

Multifunctional probes for high-throughput measurement of Seebeck coefficient and electrical conductivity at room temperature.  

PubMed

An apparatus capable of rapid measurement of the Seebeck coefficient and electrical resistivity at room temperature is reported. The novel aspect of this apparatus is the use of 4 multifunctional probes that comprise a junction of two conductors at the tip and serve as both thermocouples and electrical contacts. In addition, one of the probes has a built-in heater that can establish a temperature gradient in the sample for the Seebeck measurement. The technique does not require special sample geometries or preparation of contacts and is suitable for bulk and thin film materials. Together with automated sample stage and data acquisition, the equipment is able to measure both the Seebeck coefficient and electrical resistivity in less than 20 s with good accuracy. Less than 5% and 4% relative errors were found for the measurement of the Seebeck coefficient and electrical resistivity, respectively. This makes the apparatus especially useful for high throughput evaluation of thermoelectric materials. PMID:24784625

García-Cañadas, Jorge; Min, Gao

2014-04-01

66

Flexible X-Ray Detector Based on the Seebeck Effect  

Microsoft Academic Search

Basically, there are two main methods to detect the energy and intensity of an X-ray beam, known as the direct method and the indirect method. In the direct method, the X-rays are absorbed by a pn junction or a photoconductive layer and directly converted into an electric signal. In the indirect method, a scintillator absorbs the X-rays, and converts them

L. M. Goncalves; J. G. Rocha; S. Lanceros-Mendez

2007-01-01

67

Dependence of Seebeck coefficient on a load resistance and energy conversion efficiency in a thermoelectric composite  

SciTech Connect

The thermo-emf {delta}V and current {delta}I generated by imposing the alternating temperature gradients (ATG) at a period of T and the steady temperature gradient (STG) on a thermoelectric (TE) composite were measured as a function of t, where t is the lapsed time and T was varied from 60 to or {infinity} s. The STG and ATG were produced by imposing steadily and alternatively a source voltage V in the range from 1.0 to 4.0 V on two Peltier modules sandwiching a composite. {delta}T, {delta}V, {delta}I and V{sub P} oscillate at a period T and their waveforms vary significantly with a change of T, where {delta}V and V{sub P} are the voltage drops in a load resistance R{sub L} and in resistance R{sub P} of two modules. The resultant Seebeck coefficient |{alpha}| = |{delta}V|/{delta}T of a composite under the STG was found to be expressed as |{alpha}| = |{alpha}{sub 0}|(1 - R{sub comp}/R{sub T}), where R{sub T} is the total resistance of a circuit for measuring the output signals and R{sub comp} is the resistance of a composite. The effective generating power {delta}W{sub eff} has a local maximum at T = 960 s for the p-type composite and at T = 480 s for the n-type one. The maximum energy conversion efficiency {eta} of the p- and n-type composites under the ATG produced by imposing a voltage of 4.0 V at an optimum period were 0.22 and 0.23% at {delta}T{sub eff} = 50 K, respectively, which are 42 and 43% higher than those at {delta}T = 42 K under the STG. These maximum {eta} for a TE composite sandwiched between two Peltier modules, were found to be expressed theoretically in terms of R{sub P}, R{sub T}, R{sub L}, {alpha}{sub P} and {alpha}, where {alpha}{sub P} and {alpha} are the resultant Seebeck coefficients of Peltier modules and a TE composite.

Yamashita, Osamu [Materials Science Co. Ltd., 5-5-44 Minamikasugaoka, Ibaraki, Osaka 567-0046 (Japan)], E-mail: yamashio567@yahoo.co.jp; Odahara, Hirotaka [Advanced Materials Co. Ltd., 4-6-10 Kizuri, Higashiosaka, Osaka 577-0827 (Japan); Ochi, Takahiro; Satou, Kouji [Faculty of Engineering, Ehime University, Bunkyocho, Matsuyama 790-8577 (Japan)

2007-10-02

68

A Study of the Measurement of Seebeck Coefficient of SiGe  

NASA Technical Reports Server (NTRS)

In 1821 German Physicist Thomas J. Seebeck discovered that heat could be converted into electricity when a temperature difference was applied across two points on a material. Theoretically, the generated voltage has a directly proportional relationship with the temperature difference. This relationship is the Seebeck coefficient that scientists always referred to when determining the efficiency of a thermoelectricity convention. In our experiments, however, hysteresis loops appeared when we plotted voltage against temperature difference, and the measured Seebeck appeared differently when the measurements were run under vacuum, air, and helium gas. Measurements were done by using a low-frequency AC measuring method. By simulating the experimental setup into a; thermal circuit, we found that the loop and inconsistency in measuring Seebeck coefficient could be explained by studying the behaviors of a RC circuit in a thermal sense. Under vacuum, the gap of the hysteresis loop can be largely eliminated if the time period of the temperature difference increased up to 4800s. The trend of the variations in measuring Seebeck coefficients in different environments can also be predicted by using different thermal circuit models.

Heung, King Yi

2005-01-01

69

Macro and Micro-Scale Features of Thermoelectric PbTe (Br, Na) Systems: Micro-FTIR Spectroscopy, Micro-Seebeck Measurements, and SEM/EDX Observations  

NASA Astrophysics Data System (ADS)

In this work, n-type and p-type PbTe doped with Br and Na, respectively, were thoroughly examined to determine the effect of the dopant on microstructure. Macro and micro homogeneity of the samples were studied by means of micro-Fourier-transform infrared (micro-FTIR) spectroscopy, micro-Seebeck measurements, and scanning electron microscopy with energy-dispersive x-ray analysis (SEM/EDX). SEM/EDX observations showed the samples were not single-phase materials—second phases were created by inclusions that disturbed the coherence of the matrix and, subsequently, drastically affected the Seebeck coefficient. In a micro-scale study, local variations of sodium content were detected in Na-doped samples; in Br-doped samples a second, PbBr2, phase was observed in the PbTe matrix. A direct effect of matrix dopant on Seebeck coefficient and plasmon frequency for the Br-doped and Na-doped samples was observed by use of the three complementary techniques.

Stefanaki, E. C.; Polymeris, G. S.; Nikolic, P. M.; Papageorgiou, Ch.; Pavlidou, E.; Hatzikraniotis, E.; Kyratsi, Th.; Paraskevopoulos, K. M.

2014-05-01

70

Measurement system of the Seebeck coefficient or of the electrical resistivity at high temperature  

NASA Astrophysics Data System (ADS)

A high temperature Seebeck coefficient or electrical resistivity apparatus has been designed and fabricated to measure sample with typical size ~10 × 1 × 1 mm3. It can measure both transport properties from 300 K to 1000 K in argon atmosphere. The sample lies transversely on top of two metallic half-cylinders, which contain heating cartridges and allow temperature and thermal gradient control and reversal. The temperature gradient is measured by two type N thermocouples pressed against the upper surface of the sample. The key feature of this apparatus is the disk-shaped junction of each type N thermocouple which strongly improves the thermal contact with the sample. The Seebeck coefficient is obtained by averaging over two measured values with opposite thermal gradient directions (~+/-2 K). For the resistivity measurements, the temperature is stabilized and the temperature gradient is actively reduced below 0.2 K to make negligible any spurious thermal voltage. Uncertainties of ~3% for the Seebeck coefficient and 1% for the resistivity were obtained on Ni samples. The Seebeck coefficient and resistivity have also been measured on a skutterudite sample as small as ~7 × 1.5 × 0.5 mm3 with very good agreement with literature.

Rouleau, O.; Alleno, E.

2013-10-01

71

Measurement system of the Seebeck coefficient or of the electrical resistivity at high temperature.  

PubMed

A high temperature Seebeck coefficient or electrical resistivity apparatus has been designed and fabricated to measure sample with typical size ~10 × 1 × 1 mm(3). It can measure both transport properties from 300 K to 1000 K in argon atmosphere. The sample lies transversely on top of two metallic half-cylinders, which contain heating cartridges and allow temperature and thermal gradient control and reversal. The temperature gradient is measured by two type N thermocouples pressed against the upper surface of the sample. The key feature of this apparatus is the disk-shaped junction of each type N thermocouple which strongly improves the thermal contact with the sample. The Seebeck coefficient is obtained by averaging over two measured values with opposite thermal gradient directions (~±2 K). For the resistivity measurements, the temperature is stabilized and the temperature gradient is actively reduced below 0.2 K to make negligible any spurious thermal voltage. Uncertainties of ~3% for the Seebeck coefficient and 1% for the resistivity were obtained on Ni samples. The Seebeck coefficient and resistivity have also been measured on a skutterudite sample as small as ~7 × 1.5 × 0.5 mm(3) with very good agreement with literature. PMID:24182159

Rouleau, O; Alleno, E

2013-10-01

72

Cross-plane Seebeck coefficient and thermal conductivity of CuFeSe2 thin film  

NASA Astrophysics Data System (ADS)

The CuFeSe2 is a member of the I-III-VI2 semiconductors, whereas it shows different physical properties from the chalcopyrite family, include the tetragonal structure, the small band gap ~0.16 eV and the weak magnetic behavior. Only a few articles focused on this material in recent years. The measurements of the Seebeck coefficient and thermal conductivity of the high quality CuFeSe2 thin film could provide valuable information for its thermal application. In this report, a CuFeSe2 thin film with thickness ~200 nm on SiO2/Si substrate was prepared by pulse laser deposition (PLD). The highly crystallized film shows a preferred orientation (h 0 0) normal to the film surface. Two pairs of heater/sensor Au strips were thermally deposited on the thin film and substrate separately for thermal conductivity measurement using differential 3? method. The Seebeck coefficient across the film plane was directly measured by two additional EMF probes below and above the film with temperature gradient generated by heater/sensor at frequency 2?. The temperature dependence of thermal conductivity and Seebeck coefficient were measured in a wide temperature range from 150 to 300 K. The room-temperature thermal conductivity and Seebeck coefficient are obtained to be 3.5 W/m-K and -108 ?V/K respectively.

Lee, P. C.; Ou, M. N.; Luo, J. Y.; Wu, M. K.; Chen, Y. Y.

2012-06-01

73

Development and application of an instrument for spatially resolved Seebeck coefficient measurements  

NASA Astrophysics Data System (ADS)

The Seebeck coefficient is a key indicator of the majority carrier type (electrons or holes) in a material. The recent trend toward the development of combinatorial materials research methods has necessitated the development of a new high-throughput approach to measuring the Seebeck coefficient at spatially distinct points across any sample. The overall strategy of the high-throughput experiments is to quickly identify the region of interest on the sample at some expense of accuracy, and then study this region by more conventional techniques. The instrument for spatially resolved Seebeck coefficient measurements reported here relies on establishing a temperature difference across the entire compositionally graded thin-film and consecutive mapping of the resulting voltage as a function of position, which facilitates the temperature-dependent measurements up to 400 °C. The results of the designed instrument are verified at ambient temperature to be repeatable over 10 identical samples and accurate to within 10% versus conventional Seebeck coefficient measurements over the -100 to +150 ?V/K range using both n-type and p-type conductive oxides as test cases. The developed instrument was used to determine the sign of electrical carriers of compositionally graded Zn-Co-O and Ni-Co-O libraries prepared by combinatorial sputtering. As a result of this study, both cobalt-based materials were determined to have p-type conduction over a broad single-phase region of chemical compositions and small variation of the Seebeck coefficient over the entire investigated range of compositions and temperature.

Zakutayev, Andriy; Luciano, Frank J.; Bollinger, Vincent P.; Sigdel, Ajaya K.; Ndione, Paul F.; Perkins, John D.; Berry, Joseph J.; Parilla, Philip A.; Ginley, David S.

2013-05-01

74

Rigorous calculation of the Seebeck coefficient and mobility of thermoelectric materials  

NASA Astrophysics Data System (ADS)

The Seebeck coefficient of a typical thermoelectric material is calculated without recourse to the relaxation time approximation (RTA). To that end, the Boltzmann transport equation is solved in one spatial and two k-space coordinates by a generalization of the iterative technique first described by Rode. Successive guesses for the chemical potential profile are generated until current continuity and charge-neutrality in the bulk of the device are simultaneously satisfied. Both the mobility and Seebeck coefficient are calculated as functions of the temperature and the agreement to experimentally obtained values is found to be satisfactory. Comparison is made with the less accurate RTA result, which has the sole advantage of giving closed form expressions for the transport coefficients.

Ramu, Ashok T.; Cassels, Laura E.; Hackman, Nathan H.; Lu, Hong; Zide, Joshua M. O.; Bowers, John E.

2010-04-01

75

Measurement of Temperature-Dependent Conductivity and Seebeck Coefficient of Self-assembled Gold Nanoparticle Wires  

Microsoft Academic Search

We are exploring the electrical and thermoelectrical properties of wires composed of 12nm diameter gold nanoparticles. The wires are deposited on glass substrates via evaporation-driven vertical colloidal deposition (VCD). We then measure the temperature-dependence of the resistance and thermopower (Seebeck coefficient) between 30 and 120K. We will discuss these measurements in the context of the constituent nanoparticle size and the

J. W. Sun; J. B. Hutchison; J. A. Hoffmann; M. E. Reeves

2006-01-01

76

Simultaneous measurement of the Seebeck coefficient and thermal conductivity in the cross-sectional direction of thermoelectric thick film  

NASA Astrophysics Data System (ADS)

The measurement of the thermoelectric properties of thin film thermoelectric materials has been an issue due to the difficulty and inaccuracy. In this work, we present a new model to simultaneously extract the Seebeck coefficient and thermal conductivity in the cross-sectional direction of thin film thermoelectric material. The proposed method uses a sandwich structure composed of a metal electrode/TE film/metal electrode and measures the external Seebeck coefficient at two different intervals on the metal electrode. A theoretical model enables us to extract the Seebeck coefficient and thermal conductivity of the thermoelectric material from the two external Seebeck coefficient measurement values. The proposed method is applied to screen-printed ZnSb film with copper electrodes and the measurement results were found to lie in a reasonable range. Given that this method is simple to use, it will contribute to the development of thin film thermoelectric devices.

Jin Kim, Sun; Hyung We, Ju; Soo Kim, Gyung; Jin Cho, Byung

2012-11-01

77

Measurement of Temperature-Dependent Conductivity and Seebeck Coefficient of Self-assembled Gold Nanoparticle Wires  

NASA Astrophysics Data System (ADS)

We are exploring the electrical and thermoelectrical properties of wires composed of 12nm diameter gold nanoparticles. The wires are deposited on glass substrates via evaporation-driven vertical colloidal deposition (VCD). We then measure the temperature-dependence of the resistance and thermopower (Seebeck coefficient) between 30 and 120K. We will discuss these measurements in the context of the constituent nanoparticle size and the preparation of the deposited wire; we also make comparisons to similar measurements of bulk gold and gold-iron alloys.

Sun, J. W.; Hutchison, J. B.; Hoffmann, J. A.; Reeves, M. E.

2006-03-01

78

Infrared spectra and seebeck coefficient of LnCoO{sub 3} with the perovskite structure  

SciTech Connect

The lattice vibrations in LnCoO{sub 3} perovskites (Ln = La, Pr, Nd, Sm, Eu, or Gd) have been investigated with reference to the lattice vibrations of the ideal cubic perovskite. These vibrations at room temperature indicate the structural changes with the change in the Ln ion. These frequencies are helpful in estimating the stability of the synthesized LnCoO{sub 3} phase. The temperature dependence of vibrational frequencies and the Seebeck coefficient reveal that the crystal symmetry is unchanged and the spin transition is due to the entropy increase of the 3d electrons with rising temperature.

Kim, Yoo Young; Kwon, Tae Yun; Park, Sung Ho [Jeonju Univ., (Korea, Republic of)] [and others] [Jeonju Univ., (Korea, Republic of); and others

1994-10-01

79

Seebeck and resistance diagnostics in the ESA MSL facility for the ISS  

NASA Astrophysics Data System (ADS)

The new generation of furnaces, used to study materials in microgravity on board the International Space Station, is defined to perform long duration experiments requiring optimised growth parameters of the material under study. Seebeck and Resistance diagnostics are to be able to perform in-situ and non-invasive observations and give scientists a means to influence their experiment, thus implementing the Telescience concept. A breadboard model and an engineering model of the "Seebeck and Resistance Measurement Device" (S&RMD) have been realised under an ESA contract. Two flight models are soon to be realised. They will be placed on board the International Space Station (ISS) in 2004/2005 for use by scientists. The aim of this presentation is to inform the scientific community and programmatics managers of the performances of such a device to attract their interest in view of future scientific experiment proposals on board the International Space Station, in the ESA Materials Science Laboratory (MSL) facility. The MSL will be integrated in the NASA first Material Science Research Rack (MSRR-1), which will be installed in the US Laboratory of the ISS.

Pissard, J.-P.; Le Grand, G.; Salvi, C.; Garandet, J.-P.; Drevet, B.; Martella, M.

2002-07-01

80

Seebeck Coefficient of Manganese Oxide Nanoparticles as a Function of Ohmic Resistance  

NASA Astrophysics Data System (ADS)

Due to the ever increasing energy demand and growing global concern over the environmental impact of CO2 emissions, there is an urging need to seek solutions to transit from fossil fuels to sustainable energy. Thermoelectric (TE) materials show great promise for converting waste heat energy into electricity. TE systems have many unique advantages such as silent operationality, time reliability, and dimensional scalability. Most recently, researchers Song et al. [1] found that MnO2 nanoparticles show a giant Seebeck coefficient of S = 20 mV/K, which is100 times higher than bismuth telluride, one of the best TE materials. Song et al.[1] concluded the paper claiming that the giant S is related to the surface density of the electronic states (DOS). However, they provided very little information about the S as a function of Ohmic resistance [R] for different nano particle sizes which can give information about the DOS. Our preliminary results show that there is a sudden increase of S from 0.33-0.63 mV/K as R increases from 80-110 Ohms. This transition has never been seen before and it can give clues as to the existence of the Giant S observed in this material.[4pt] [1] F. Song, L. Wu and S. Liang, Giant Seebeck coefficient thermoelectric device of MnO2 powder, Nano. 23, 085401 (2012).

Francis, Nicholas; Hedden, Morgan; Constantin, Costel

2013-03-01

81

Improvement of Thermoelectric Properties of PEDOT/PSS Films by Addition of Gold Nanoparticles: Enhancement of Seebeck Coefficient  

NASA Astrophysics Data System (ADS)

Thermoelectric properties of hybrid films composed of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) and gold nanoparticles (AuNPs) stabilized with 3-mercaptopropinoic acid (Au-MPA NPs) and 6-mercaptohexanoic acid (Au-MHA NPs) were investigated. Several factors such as the size and content of the AuNPs, and the chain length of the NP stabilizer were found to influence the thermoelectric properties of the hybrid film. The Seebeck coefficient can be raised by varying the size of the Au-MPA NPs or the content of Au-MHA NPs. The enhancement in the Seebeck coefficient is suggested to be a result of reduced carrier concentration due to the increased number of AuNPs. This could be the first report on the fact that AuNPs enhance the Seebeck coefficient in PEDOT/PSS hybrid films.

Toshima, Naoki; Jiravanichanun, Nattha

2013-07-01

82

Carrier Concentrations and Seebeck Measurements on CuSc_1-xMg_xO_2+y Transparent Conductive Thin Films  

Microsoft Academic Search

A series of seven magnesium-doped copper scandium oxide films were made by radio frequency sputtering, and intercalated at various oxygen pressures to create different oxygen concentrations in each film. Results of the room temperature Seebeck measurements show that the p-type nature of the carriers persists for all intercalation pressures. Small Seebeck coefficients characteristic of metals corresponded to high oxygen intercalation

Dara L. Easley; Janet Tate; Allen L. Wasserman

2003-01-01

83

Enhanced seebeck coefficient for a compressive n-type polysilicon film  

NASA Astrophysics Data System (ADS)

An enhanced Seebeck coefficient (S) for a compressive n-type polysilicon film is proposed. An approximate value for S of 260 ?V/K for a polysilicon film fabricated on a gate oxide (polyGOI) is greater than the value of 210 ?V/K for a polysilicon film fabricated on a field oxide (polyFOX). The cause for this difference in the value of S is attributed to the two ends of the upward polyGOI edge caused by the local oxidation of silicon process that induces a compressive stress in the polysilicon film relative to the polyFOX. A four-point bending experiment also provides strong evidence for the enhancement in S.

Kang, Ting-Kuo

2014-01-01

84

Giant Seebeck coefficient thermoelectric device of MnO2 powder.  

PubMed

We report a giant Seebeck coefficient (S) thermoelectric (TE) material-MnO(2) powder-and the design of a practical MnO(2) TE generator to light up a regular light emitting diode (LED). The S of MnO(2) powder was measured to be higher than 20,000 ?V K(-1), which is about 100 times higher than the state-of-the-art of Bi(2)Te(3), one of the best TE materials. The giant S is very possibly closely related to the surface density of the electronic state (DOS), the Fermi energy level. The very high S and therefore high power factor is technologically important for transient TE cooling. PMID:22293218

Song, FangFang; Wu, Liming; Liang, S

2012-03-01

85

Large Seebeck coefficients of protonated titanate nanotubes for high-temperature thermoelectric conversion.  

PubMed

Titanate nanotubes Na(2-x)H(x)Ti(3)O(7) produced by alkali hydrothermally treated ground TiO(2) aerogels are investigated as possible materials for high-temperature thermoelectric conversion by measuring their thermoelectric properties. Strikingly, the Seebeck coefficients increased sharply in the temperature range 745 to 1032 K, reaching a maximum of 302 muV/K. The electrical resistivity of the TNNTs ranged from 325 to 525 Omegam, which is lower than that of bulk TiO(2), and thermal conductivities at room temperature were also very low, ranging from 0.55 to 0.75 Wm(-1) K(-1). The hollow structure of the titanate nanotubes, with small, uniform diameters, is thought to be responsible for the ultralow thermal conductivity. The large thermoelectric power and ultralow thermal conductivity suggest that titanate nanotubes represent a new kind of p-type oxide thermoelectric material. PMID:20735107

Miao, L; Tanemura, S; Huang, R; Liu, C Y; Huang, C M; Xu, G

2010-08-01

86

Use of Photothermally Generated Seebeck Voltage for Thermal Characterization of Thermoelectric Materials  

NASA Astrophysics Data System (ADS)

A simple and accurate experimental procedure to measure simultaneously the thermal properties (conductivity, diffusivity, and effusivity) of thermoelectric (TE) materials using their Seebeck voltage is proposed. The technique is based on analysis of a periodically oscillating thermoelectric signal generated from a TE material when it is thermally excited using an intensity-modulated laser source. A self-normalization procedure is implemented in the presented method using TE signals generated by changing the laser heating from one side to another of the TE material. Experiments are done on a polyaniline carbon nanohybrid (6.6 wt.% carbon nanotubes), yielding a thermal conductivity of 1.106 ± 0.001 W/m-K. The results are compared with the results from photothermal infrared radiometry experiments.

Kuriakose, Maju; Depriester, Michael; King, Roch Chan Yu; Roussel, Frédérick; Sahraoui, Abdelhak Hadj

2014-06-01

87

Apparatus for measuring Seebeck coefficient and electrical resistivity of small dimension samples using infrared microscope as temperature sensor.  

PubMed

An apparatus for measuring the Seebeck coefficient (?) and electrical resistivity (?) was designed to operate under an infrared microscope. A unique feature of this apparatus is its capability of measuring ? and ? of small-dimension (sub-millimeter) samples without the need for microfabrication. An essential part of this apparatus is a four-probe assembly that has one heated probe, which combines the hot probe technique with the Van der Pauw method for "simultaneous" measurements of the Seebeck coefficient and electrical resistivity. The repeatability of the apparatus was investigated over a temperature range of 40 °C-100 °C using a nickel plate as a standard reference. The results show that the apparatus has an uncertainty of ±4.9% for Seebeck coefficient and ±5.0% for electrical resistivity. The standard deviation of the apparatus against a nickel reference sample is -2.43 ?VK(-1) (-12.5%) for the Seebeck coefficient and -0.4 ?? cm (-4.6%) for the electrical resistivity, respectively. PMID:23742579

Jaafar, W M N Wan; Snyder, J E; Min, Gao

2013-05-01

88

Measurement of the high-temperature Seebeck coefficient of thin films by means of an epitaxially regrown thermometric reference material.  

PubMed

The Seebeck coefficient of a typical thermoelectric material, silicon-doped InGaAs lattice-matched to InP, is measured over a temperature range from 300 K to 550 K. By depositing and patterning a thermometric reference bar of silicon-doped InP adjacent to a bar of the material under test, temperature differences are measured directly. This is in contrast to conventional two-thermocouple techniques that subtract two large temperatures to yield a small temperature difference, a procedure prone to errors. The proposed technique retains the simple instrumentation of two-thermocouple techniques while eliminating the critical dependence of the latter on good thermal contact. The repeatability of the proposed technique is demonstrated to be ±2.6% over three temperature sweeps, while the repeatability of two-thermocouple measurements is about ±5%. The improved repeatability is significant for reliable reporting of the ZT figure of merit, which is proportional to the square of the Seebeck coefficient. The accuracy of the proposed technique depends on the accuracy with which the high-temperature Seebeck coefficient of the reference material may be computed or measured. In this work, the Seebeck coefficient of the reference material, n+ InP, is computed by rigorous solution of the Boltzmann transport equation. The accuracy and repeatability of the proposed technique can be systematically improved by scaling, and the method is easily extensible to other material systems currently being investigated for high thermoelectric energy conversion efficiency. PMID:23020392

Ramu, Ashok T; Mages, Phillip; Zhang, Chong; Imamura, Jeffrey T; Bowers, John E

2012-09-01

89

Enhancement of Seebeck Coefficient in Bi0.5Sb1.5Te3 with High-Density Tellurium Nanoinclusions  

NASA Astrophysics Data System (ADS)

Bi0.5Sb1.5Te3 films with homogeneously dispersed ?15 nm Te nanoparticles were prepared by the alternate deposition of Bi0.5Sb1.5Te3 layers and Te nanoparticles. As the amount of Te nanoinclusions increased to 15 vol %, the Seebeck coefficient increased from 169 to 248 µV/K. The authors concluded that the high-density Te nanoinclusions result in a carrier energy filtering effect in Bi0.5Sb1.5Te3. Consequently, the thermoelectric power factor was enhanced by 30% despite a reduction in electrical conductivity. The improvement of the power factor implies the enhancement of the thermoelectric figure of merit ZT, providing the possibility of further ZT improvement by embedding Te nanoinclusions in Bi0.5Sb1.5Te3 bulk materials.

Kim, Sang Il; Ahn, Kyunghan; Yeon, Dong-Hee; Hwang, Sungwoo; Kim, Hyun-Sik; Mock Lee, Sang; Lee, Kyu Hyoung

2011-09-01

90

Thermoelectric performance of poly(3-hexylthiophene) films doped by iodine vapor with promising high seebeck coefficient  

NASA Astrophysics Data System (ADS)

Poly(3-hexylthiophene) (P3HT) films doped with iodine vapor have been prepared by casting a P3HT solution on glass substrates and their thermoelectric (TE) performances has been investigated. The maximum Seebeck coefficient and electrical conductivity of iodine-doped P3HT films were 386 µV·K-1 (at room temperature) and 4.7 × 10-1 S·cm-1, which is about five orders of magnitude higher than that of pristine P3HT films. The power factor of these iodine-doped P3HT films was estimated to be 7.0 µW·m-1·K-2 at room temperature, which is a relative high value for organic TE materials. The UV-vis spectra of iodine-doped P3HT films showed a slight red shift of the iodine-doped P3HT compared to those of pristine P3HT films. Atomic force microscopy images indicated the conformational changes in P3HT chains after treatment with iodine vapor. During this treatment, the P3HT chains self-organized into a more ordered structure, this organization improved the charge carrier transport capability and the TE performance of P3HT the films.

Zhu, Hongfei; Liu, Congcong; Song, Haijun; Xu, Jingkun; Kong, Fangfang; Wang, Jianmin

2014-03-01

91

Measurement setup for the simultaneous determination of diffusivity and Seebeck coefficient in a multi-anvil apparatus.  

PubMed

In this paper, a high pressure setup is presented for performing simultaneous measurements of Seebeck coefficient and thermal diffusivity in multianvil apparatus for the purpose of enhancing the study of transport phenomena. Procedures for the derivation of Seebeck coefficient and thermal diffusivity/conductivity, as well as their associated sources of errors, are presented in detail, using results obtained on the filled skutterudite, Ce(0.8)Fe(3)CoSb(12,) up to 12 GPa at ambient temperature. Together with recent resistivity and sound velocity measurements in the same apparatus, these developments not only provide the necessary data for a self-consistent and complete characterization of the figure of merit of thermoelectric materials under pressure, but also serve as an important tool for furthering our knowledge of the dynamics and interplay between these transport phenomena. PMID:23020390

Jacobsen, M K; Liu, W; Li, B

2012-09-01

92

In-situ conductivity and Seebeck measurements of highly efficient n-dopants in fullerene C60  

NASA Astrophysics Data System (ADS)

We present two organic dimetal complexes Cr2(hpp)4 and W2(hpp)4 as n-dopants investigated in the model system of fullerene C60 for the application in organic electronic devices. Conductivity and Seebeck measurements on doped layers are carried out in vacuum at different doping concentrations and various substrate temperatures to compare the two dopants. Very high conductivities of up to 4 S/cm are achieved for both organic dopants. The thermal activation energy of the conductivity as well as the measured Seebeck coefficient are found to decrease with increasing doping concentration, indicating a shift of the Fermi level towards the electron transport level of the n-doped C60.

Menke, Torben; Ray, Debdutta; Meiss, Jan; Leo, Karl; Riede, Moritz

2012-02-01

93

Measurement setup for the simultaneous determination of diffusivity and Seebeck coefficient in a multi-anvil apparatus  

NASA Astrophysics Data System (ADS)

In this paper, a high pressure setup is presented for performing simultaneous measurements of Seebeck coefficient and thermal diffusivity in multianvil apparatus for the purpose of enhancing the study of transport phenomena. Procedures for the derivation of Seebeck coefficient and thermal diffusivity/conductivity, as well as their associated sources of errors, are presented in detail, using results obtained on the filled skutterudite, Ce0.8Fe3CoSb12, up to 12 GPa at ambient temperature. Together with recent resistivity and sound velocity measurements in the same apparatus, these developments not only provide the necessary data for a self-consistent and complete characterization of the figure of merit of thermoelectric materials under pressure, but also serve as an important tool for furthering our knowledge of the dynamics and interplay between these transport phenomena.

Jacobsen, M. K.; Liu, W.; Li, B.

2012-09-01

94

Evaluation of Seebeck coefficients in n- and p-type silicon nanowires fabricated by complementary metal-oxide-semiconductor technology  

NASA Astrophysics Data System (ADS)

Silicon-based thermoelectric nanowires were fabricated by using complementary metal-oxide-semiconductor (CMOS) technology. 50 nm width n- and p-type silicon nanowires (SiNWs) were manufactured using a conventional photolithography method on 8 inch silicon wafer. For the evaluation of the Seebeck coefficients of the silicon nanowires, heater and temperature sensor embedded test patterns were fabricated. Moreover, for the elimination of electrical and thermal contact resistance issues, the SiNWs, heater and temperature sensors were fabricated monolithically using a CMOS process. For validation of the temperature measurement by an electrical method, scanning thermal microscopy analysis was carried out. The highest Seebeck coefficients were - 169.97 ?V K-1 and 152.82 ?V K-1 and the highest power factors were 2.77 mW m-1 K-2 and 0.65 mW m-1 K-2 for n- and p-type SiNWs, respectively, in the temperature range from 200 to 300 K. The larger power factor value for n-type SiNW was due to the higher electrical conductivity. The total Seebeck coefficient and total power factor for the n- and p-leg unit device were 157.66 ?V K-1 and 9.30 mW m-1 K-2 at 300 K, respectively.

Hyun, Younghoon; Park, Youngsam; Choi, Wonchul; Kim, Jaehyeon; Zyung, Taehyoung; Jang, Moongyu

2012-10-01

95

A Thermoelectric Investigation of Selected Lead Salts and the Spin-Seebeck Effect in Semiconductors  

NASA Astrophysics Data System (ADS)

The dimensionless thermoelectric figure of merit, zT, is used to characterize the conversion efficiency of thermoelectric materials. In this dissertation, we include experimental results on new p-type semiconducting alloys based on lead telluride that have higher zT values than historical materials. Through alloying PbTe:Tl with sulfur, we demonstrate an increase in zT over the parent material PbTe:Tl. Next, we remove the toxic element T1 from the PbTe/PbS alloy and retain the high efficiency via doping heavy valence band in PbTe, a separate mechanism than the high-zT resonant level doping achieved by the impurity Tl. We present experimental evidence relevant to the valence band structure of PbTe alloys at elevated temperature and demonstrate that these alloys remain direct gap semiconductors at temperatures relevant to automotive thermoelectric waste heat recovery (<850K).

Jaworski, Christopher M.

96

Seebeck effect in Fe1+xTe1-ySey single crystals  

NASA Astrophysics Data System (ADS)

We present measurements of resistivity and thermopower S of Fe1+xTe1-ySey single crystalline samples with y=0 , 0.1, 0.2, 0.3, and 0.45 in zero field and in a magnetic field B=8T . We find that the shape of thermopower curves appears quite peculiar in respect to that measured in other Fe-based superconducting families. We propose a qualitative analysis of the temperature behavior of S , where the samples are described as almost compensated semimetals: different electron and hole bands with similar carrier concentrations compete and their relative contribution to the thermoelectric transport depends on the respective filling, mobility, and coupling with phonons. For y?0.2 , superconductivity occurs and the optimum Se-doping level for a maximum Tc of 13 K turns out to be y=0.3 . At low temperatures, evidence of a contribution to S by an excitation-drag mechanism is found while at high temperatures a strikingly flat behavior of S is explained within a narrow-band Hubbard model.

Pallecchi, I.; Lamura, G.; Tropeano, M.; Putti, M.; Viennois, R.; Giannini, E.; van der Marel, D.

2009-12-01

97

Nernst and Seebeck Coefficients of the Cuprate Superconductor YBa2Cu3O6.67: A Study of Fermi Surface Reconstruction  

NASA Astrophysics Data System (ADS)

The Seebeck and Nernst coefficients S and ? of the cuprate superconductor YBa2Cu3Oy (YBCO) were measured in a single crystal with doping p=0.12 in magnetic fields up to H=28T. Down to T=9K, ? becomes independent of field by H?30T, showing that superconducting fluctuations have become negligible. In this field-induced normal state, S/T and ?/T are both large and negative in the T?0 limit, with the magnitude and sign of S/T consistent with the small electronlike Fermi surface pocket detected previously by quantum oscillations and the Hall effect. The change of sign in S(T) at T?50K is remarkably similar to that observed in La2-xBaxCuO4, La2-x-yNdySrxCuO4, and La2-x-yEuySrxCuO4, where it is clearly associated with the onset of stripe order. We propose that a similar density-wave mechanism causes the Fermi surface reconstruction in YBCO.

Chang, J.; Daou, R.; Proust, Cyril; Leboeuf, David; Doiron-Leyraud, Nicolas; Laliberté, Francis; Pingault, B.; Ramshaw, B. J.; Liang, Ruixing; Bonn, D. A.; Hardy, W. N.; Takagi, H.; Antunes, A. B.; Sheikin, I.; Behnia, K.; Taillefer, Louis

2010-02-01

98

Nernst and Seebeck coefficients of the cuprate superconductor YBa2Cu3O6.67: a study of Fermi surface reconstruction.  

PubMed

The Seebeck and Nernst coefficients S and nu of the cuprate superconductor YBa{2}Cu{3}O{y} (YBCO) were measured in a single crystal with doping p=0.12 in magnetic fields up to H=28 T. Down to T=9 K, nu becomes independent of field by H approximately 30 T, showing that superconducting fluctuations have become negligible. In this field-induced normal state, S/T and nu/T are both large and negative in the T-->0 limit, with the magnitude and sign of S/T consistent with the small electronlike Fermi surface pocket detected previously by quantum oscillations and the Hall effect. The change of sign in S(T) at T approximately 50 K is remarkably similar to that observed in La2-xBaxCuO4, La{2-x-y}Nd{y}Sr_{x}CuO{4}, and La{2-x-y}Eu{y}Sr{x}CuO{4}, where it is clearly associated with the onset of stripe order. We propose that a similar density-wave mechanism causes the Fermi surface reconstruction in YBCO. PMID:20366789

Chang, J; Daou, R; Proust, Cyril; Leboeuf, David; Doiron-Leyraud, Nicolas; Laliberté, Francis; Pingault, B; Ramshaw, B J; Liang, Ruixing; Bonn, D A; Hardy, W N; Takagi, H; Antunes, A B; Sheikin, I; Behnia, K; Taillefer, Louis

2010-02-01

99

Nernst and Seebeck coefficients of the iron-pncitide superconductor Ba1-xKxFe2As2  

NASA Astrophysics Data System (ADS)

The Nernst and Seebeck coefficients of the iron-pnictide superconductor Ba1-xKxFe2As2 were measured in single crystals for K concentrations ranging from the parent compound at x=0 to the optimally-doped superconductor at x=0.40, where Tc=38 K. Both coefficients show sharp anomalies at TN, the onset temperature for antiferromagnetic order. This allows us to track the doping dependence of TN and hence to map out the T-x phase diagram of Ba1-xKxFe2As2. The reconstruction of the Fermi surface by the antiferromagnetic order causes a huge enhancement of the quasiparticle Nernst signal, suggesting that carrier density and Fermi temperature are dramatically reduced in the magnetic phase. The Nernst signal due to superconducting fluctuations is small by comparison, and it remains detectable up to a temperature approximately 15% above Tc, in the optimally-doped sample.

Luo, Xigang; Shakeripour, H.; Chang, J.; Laliberte, F.; Reid, J.-Ph.; Doiron-Leyraud, N.; Taillefer, L.; Tanatar, M. A.; Prozorov, R.; Luo, H. Q.; Wang, Z. S.; Wen, H.-H.

2011-03-01

100

Seebeck and figure of merit enhancement in nanostructured antimony telluride by antisite defect suppression through sulfur doping.  

PubMed

Antimony telluride has a low thermoelectric figure of merit (ZT < ?0.3) because of a low Seebeck coefficient ? arising from high degenerate hole concentrations generated by antimony antisite defects. Here, we mitigate this key problem by suppressing antisite defect formation using subatomic percent sulfur doping. The resultant 10-25% higher ? in bulk nanocrystalline antimony telluride leads to ZT ? 0.95 at 423 K, which is superior to the best non-nanostructured antimony telluride alloys. Density functional theory calculations indicate that sulfur increases the antisite formation activation energy and presage further improvements leading to ZT ? 2 through optimized doping. Our findings are promising for designing novel thermoelectric materials for refrigeration, waste heat recovery, and solar thermal applications. PMID:22891784

Mehta, Rutvik J; Zhang, Yanliang; Zhu, Hong; Parker, David S; Belley, Matthew; Singh, David J; Ramprasad, Ramamurthy; Borca-Tasciuc, Theodorian; Ramanath, Ganpati

2012-09-12

101

Thermal Conductivity, Electrical Resistivity and Seebeck Coefficient of High Purity Iron and Selected Iron Alloys from 90 K to 400 K.  

National Technical Information Service (NTIS)

The thermal conductivity, electrical resistivity, and Seebeck coefficient of high-purity iron, two iron--chromium alloys, one iron--nickel alloy, and one iron--chromium--nickel alloy were measured over the temperature range from 90 K to 400 K. Smoothed va...

T. K. Holder

1977-01-01

102

Thermal Conductivity, Electrical Resistivity and Seebeck Coefficient of High Purity Iron and Selected Iron Alloys from 90 K to 400 K.  

National Technical Information Service (NTIS)

The thermal conductivity, electrical resistivity, and Seebeck coefficient of high purity iron, two iron-chromium alloys, one iron-nickel alloy, and one iron-chromium-nickel alloy were measured over the temperature range from 90 K to 400 K. Smoothed values...

T. K. Holder

1977-01-01

103

Radial electric field effect on thermoelectric transport properties of Bi 2Te 3 cylindrical nanowire coaxial structure  

Microsoft Academic Search

Radial electric field effect (REFE) on the thermoelectric figure of merit and Seebeck coefficient S are studied for a coaxial cylindrical capacitor configuration on the basis of bipolar intrinsic semiconductors. Theoretical analysis of REFE nanowire was done based on Poisson's equation in cylindrical geometry with corresponding boundary conditions. Using Newton's method the radial variation of the local Seebeck coefficient, carrier

V. G. Kantser; I. M. Bejenari; D. F. Meglei

2006-01-01

104

Thermal conductivity and Seebeck coefficient of 12CaO?7Al2O3 electride with a cage structure  

NASA Astrophysics Data System (ADS)

Thermal conductivity (?) and Seebeck coefficient (?) of electron-doped light-metal oxide 12CaO?7Al2O3 (C12A7 electride) with a subnanometer-sized cage structure are reported on single crystals with various electron concentrations (Ne) . The semiconducting C12A7 electride exhibits n -type conduction with the highest ? value of -100?VK-1 at 300 K. The ? exhibits an amorphouslike T2 dependence at low temperatures and varies between 2.3 and 4.5Wm-1K-1 at 300 K. This is an order-of-magnitude lower than that of the constituents, CaO (15Wm-1K-1) and Al2O3 (30Wm-1K-1) . These properties are attributed to the cage structure, suggesting that the semiconducting electride should be regarded as a phonon glass and electron crystal material. The thermoelectric performance of electrides evaluated by a dimensionless figure of merit (ZT) shows an optimized value of 2×10-3 at 300 K for the semiconducting electride with Ne of 5×1020cm-3 .

Kim, Sung Wng; Tarumi, Ryuichi; Iwasaki, Hideo; Ohta, Hiromichi; Hirano, Masahiro; Hosono, Hideo

2009-08-01

105

The fabrication of thermoelectric La0.95Sr0.05CoO3 nanofibers and Seebeck coefficient measurement.  

PubMed

The P-type perovskite oxides La(1-x)Sr(x)CoO(3) are a promising group of complex oxide thermoelectric (TE) materials. The thermoelectric properties of these oxides are expected to be significantly improved when their critical dimensions are reduced to the nanoscale. In this paper, the La(0.95)Sr(0.05)CoO(3) nanofibers, with diameters in the range of approximately 35 nm, were successfully prepared by the electrospinning process. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize these thermoelectric nanofibers. A micro-electromechanical (MEMS) tester was designed and fabricated to measure the Seebeck coefficient of the nanofibers. The measured voltage output was as large as 1.7 mV and the obtained Seebeck coefficient of the nanofibers reached 650 microV K(-1). PMID:20820092

Xu, Weihe; Shi, Yong; Hadim, Hamid

2010-10-01

106

Semi-analytical model for the Seebeck coefficient in semiconductors with isotropic DOS given by a power function  

NASA Astrophysics Data System (ADS)

The relations for the Seebeck coefficient in a semiconductor with the isotropic density of states given by a power function are introduced within the scope of a semi-analytical model, which is based on the theoretical relations given by the foundations of the semiconductor physics as well as on experimentally defined temperature dependences of various semiconductor characteristics, but does not include any adjustable parameters. Between those characteristics the major role plays the intrinsic carrier concentration. It was demonstrated that although the introduced model is based on the simplified Maxwell-Boltzmann statistic, it is not compromised by this choice. A comparison with experimental data for five different semiconductors proves its ability to provide reliable predictions over a wide range of parameters (temperature, dopant type and concentration) not only for non-degenerated wide bandgap semiconductors (Si, Ge) but also for InAs, which represents partly degenerated narrow bandgap semiconductors with a non-parabolic density of states. Even in the case of a HgCdTe, with its extremely narrow bandgap and complex temperature dependence of the carrier concentration, the model is in good agreement with experimental data. The semi-analytical nature of the introduced model and its dependence on the abundance and reliability of the used experimental data were discussed on the example of Bi2Te3. Although the relative deficiency and controversy of the experimental results in this case significantly impede the model's applicability, it is still able to give at least qualitative predictions, which are nevertheless better than the results of the calculation of the thermopower from first principles. Being primarily addressed to the experimental community, the model provides simple relations in the case of the parabolic non-intrinsic semiconductor for thermoelectric voltage and for optimal dopant concentration for the thermogenerator within the known working temperature range, which can be useful in real-life `energy harvesting' applications.

Ibragimov, A.

2012-11-01

107

Effect of off-stoichiometry on the transport properties of the Heusler-type Fe2VAl compound  

Microsoft Academic Search

We report on the effect of off-stoichiometry on the temperature dependence of electrical resistivity, the Seebeck coefficient, and the Hall coefficient in the Heusler-type Fe2VAl compound. While the stoichiometric Fe2VAl exhibits a semiconductorlike resistivity behavior, a small deviation of the Al content from stoichiometry causes a significant decrease in the low-temperature resistivity and a large enhancement in the Seebeck coefficient.

Y. Nishino; H. Kato; M. Kato; U. Mizutani

2001-01-01

108

Hall, Seebeck, and Nernst Coefficients of Underdoped HgBa2CuO4+?: Fermi-Surface Reconstruction in an Archetypal Cuprate Superconductor  

NASA Astrophysics Data System (ADS)

Charge-density-wave order has been observed in cuprate superconductors whose crystal structure breaks the square symmetry of the CuO2 planes, such as orthorhombic YBa2Cu3Oy (YBCO), but not so far in cuprates that preserve that symmetry, such as tetragonal HgBa2CuO4+? (Hg1201). We have measured the Hall (RH), Seebeck (S), and Nernst (?) coefficients of underdoped Hg1201 in magnetic fields large enough to suppress superconductivity. The high-field RH(T) and S(T) are found to drop with decreasing temperature and become negative, as also observed in YBCO at comparable doping. In YBCO, the negative RH and S are signatures of a small electron pocket caused by Fermi-surface reconstruction, attributed to charge-density-wave modulations observed in the same range of doping and temperature. We deduce that a similar Fermi-surface reconstruction takes place in Hg1201, evidence that density-wave order exists in this material. A striking similarity is also found in the normal-state Nernst coefficient ?(T), further supporting this interpretation. Given the model nature of Hg1201, Fermi-surface reconstruction appears to be common to all hole-doped cuprates, suggesting that density-wave order is a fundamental property of these materials.

Doiron-Leyraud, Nicolas; Lepault, S.; Cyr-Choinière, O.; Vignolle, B.; Grissonnanche, G.; Laliberté, F.; Chang, J.; Bariši?, N.; Chan, M. K.; Ji, L.; Zhao, X.; Li, Y.; Greven, M.; Proust, C.; Taillefer, Louis

2013-04-01

109

Upper critical field, superconducting energy gaps and the Seebeck coefficient in La(0.8)Th(0.2)FeAsO.  

PubMed

We report the synthesis and characterization of a new electron-doped La-oxypnictide superconductor by partial substitution of lanthanum by thorium. The superconducting transition temperature at about 30.3 K was observed in La(0.8)Th(0.2)FeAsO, which is the highest in La-based oxypnictide superconductors synthesized at ambient pressure. We find that the decrease in lattice parameters with Th doping in LaOFeAs is more drastic as compared to that obtained by high pressure (6 GPa) synthesis of oxygen-deficient LaOFeAs. The resistivity and magnetic susceptibility measurements yield an upper critical field H(c2)(0) of 47 T. Partial substitution of Th in place of La induces electron doping, as shown by a negative Seebeck coefficient. The temperature-dependent magnetic penetration depth data provides strong evidence for a nodeless low energy gap of 1.4 meV. PMID:21825433

Prakash, J; Singh, S J; Patnaik, S; Ganguli, A K

2009-04-29

110

Ratchet effects in graphene and quantum wells with lateral superlattice  

NASA Astrophysics Data System (ADS)

Theoretical and experimental studies on the ratchet effects in graphene and in quantum wells with a lateral superlattice excited by alternating electric fields of terahertz frequency range are presented. We discuss the Seebeck ratchet effect and helicity driven photocurrents and show that the photocurrent generation is based on the combined action of a spatially periodic in-plane potential and a spatially modulated light.

Golub, L. E.; Nalitov, A. V.; Ivchenko, E. L.; Olbrich, P.; Kamann, J.; Eroms, J.; Weiss, D.; Ganichev, S. D.

2013-12-01

111

Thermoelectric effects in magnetic nanostructures  

Microsoft Academic Search

We model and evaluate the Peltier and Seebeck effects in magnetic multilayer nanostructures by a finite-element theory of thermoelectric properties. We present analytical expressions for the thermopower and the current-induced temperature changes due to Peltier cooling\\/heating. The thermopower of a magnetic element is in general spin polarized, leading to spin-heat coupling effects. Thermoelectric effects in spin valves depend on the

Moosa Hatami; Gerrit E. W. Bauer; Qinfang Zhang; Paul J. Kelly

2009-01-01

112

Doping effects on thermoelectric properties of the off-stoichiometric Heusler compounds Fe2-xV1+xAl  

NASA Astrophysics Data System (ADS)

The thermoelectric properties of Heusler-type Fe2-xV1+xAl1-ySiy and Fe2-xV1+x-yTiyAl alloys have been investigated to clarify which off-stoichiometric alloy, i.e., V-rich (x > 0) or V-poor (x < 0), is more effective in enhancing the Seebeck coefficient when doped by Si and Ti, while retaining a low electrical resistivity. Large Seebeck coefficients of -182 ?V/K and 110 ?V/K at 300 K are obtained for n-type Fe1.95V1.05Al0.97Si0.03 and p-type Fe2.04V0.93Ti0.03Al, respectively. When the Seebeck coefficient is plotted as a function of valence electron concentration (VEC), the VEC dependence for the doped off-stoichiometric alloys falls on characteristic curves depending on the off-stoichiometric composition x. It is concluded that a larger Seebeck coefficient with a negative sign can be obtained for the V-rich alloys rather than the V-poor alloys, whilst good p-type materials are always derived from the V-poor alloys. Substantial enhancements in the Seebeck coefficient for the off-stoichiometric alloys could be achieved by a favorable modification in the electronic structure around the Fermi level through the antisite V or Fe defect formation.

Nishino, Y.; Tamada, Y.

2014-03-01

113

Transport Magnetic Proximity Effects in Platinum  

NASA Astrophysics Data System (ADS)

Platinum (Pt) metal, being nonmagnetic and with a strong spin-orbit coupling interaction, has been central in detecting the pure spin current and establishing most of the recent spin-based phenomena. Magnetotransport measurements, both electrical and thermal, conclusively show strong ferromagnetic characteristics in thin Pt films on the ferromagnetic insulator due to the magnetic proximity effects. The pure spin current phenomena measured by Pt, including the inverse spin Hall and the spin Seebeck effects, are thus contaminated and not exclusively established.

Huang, S. Y.; Fan, X.; Qu, D.; Chen, Y. P.; Wang, W. G.; Wu, J.; Chen, T. Y.; Xiao, J. Q.; Chien, C. L.

2012-09-01

114

Perfect spin filtering and large spin thermoelectric effects in organic transition-metal molecular junctions.  

PubMed

We present ab initio studies of spin-polarized transport properties and thermospin effects in cyclopentadienyl-iron molecular junctions. It is found that the spin-up transmission coefficient at the Fermi level shows an odd-even oscillating behaviour, while the spin-down transmission coefficient has an exponential decay with the molecule length. The spin polarization at the Fermi level rapidly tends toward a saturation value close to 100% with the molecule length. This is ascribed to the existence of different orbital states for different spin components at the Fermi level. In addition, we find that the spin-up Seebeck coefficient oscillates between positive and negative values, while the spin-down Seebeck coefficient always has a positive value and monotonically increases with the molecule length. Therefore in some cases, the spin Seebeck coefficient is even larger than the corresponding charge Seebeck effect. Finally, we also provide a possibility of utilizing cyclopentadienyl-iron molecular junctions to achieve the pure spin current without an accompanying charge current at about room temperature. PMID:24788691

Yang, X F; Liu, Y S; Zhang, X; Zhou, L P; Wang, X F; Chi, F; Feng, J F

2014-06-21

115

Peltier effect in doped silicon microchannel plates  

NASA Astrophysics Data System (ADS)

The Seebeck coefficient is determined from silicon microchannel plates (Si MCPs) prepared by photo-assisted electrochemical etching at room temperature (25 °C). The coefficient of the sample with a pore size of 5 × 5 ?m2, spacing of 1 ?m and thickness of about 150 ?m is -852 ?V/K along the edge of the square pore. After doping with boron and phosphorus, the Seebeck coefficient diminishes to 256 ?V/K and -117 ?V/K along the edge of the square pore, whereas the electrical resistivity values are 7.5 × 10-3 ?·cm and 1.9 × 10-3 ?·cm, respectively. Our data imply that the Seebeck coefficient of the Si MCPs is related to the electrical resistivity and is consistent with that of bulk silicon. Based on the boron and phosphorus doped samples, a simple device is fabricated to connect the two type Si MCPs to evaluate the Peltier effect. When a proper current passes through the device, the Peltier effect is evidently observed. Based on the experimental data and the theoretical calculation, the estimated intrinsic figure of merit ZT of the unicouple device and thermal conductivity of the Si MCPs are 0.007 and 50 W/(m·K), respectively.

Pengliang, Ci; Jing, Shi; Fei, Wang; Shaohui, Xu; Zhenya, Yang; Pingxiong, Yang; Lianwei, Wang; Chen, Gao; Chu, Paul K.

2011-12-01

116

Analysis of Residual Acceleration Effects on Transport and Segregation During Directional Solidification of Tin-Bismuth in the MEPHISTO Furnace Facility  

NASA Technical Reports Server (NTRS)

The objective of this work is to approach the problem of determining the transport conditions (and effects of residual acceleration) during the plane-front directional solidification of a tin-bismuth alloy under low gravity conditions. The work involves using a combination of 2- and 3-D numerical models, scaling analyses, ID models and the results of ground-based and low-gravity experiments. The latter are to be conducted during the MEPHISTO experiment scheduled for USMP-3 in early 1996. The models will be used to predict the response of the transport conditions and consequent solute segregation in directionally solidifying tin-bismuth melt. Real-time Seebeck voltage variations across a Sn-Bi melt during directional solidification in MEPHISTO on USMP-1 show a distinct variation which can be correlated with thruster firings. The Seebeck voltage measurement is related to the response of the instantaneous average melt composition at the melt-solid interface. This allows a direct comparison of numerical simulations with the Seebeck signals obtained on USMP-1. The effects of such accelerations on composition for a directionally solidifying Sn-Bi alloy have been simulated numerically. USMP-1 acceleration data was used to assist in our choice of acceleration magnitude and orientation. The results show good agreement with experimental observations. The USMP-3 experiments took place earlier this year (February 22 through March 6). There were several differences between the USMP-3 experiments as compared to USMP-1. Firstly a more concentrated alloy was solidified and, secondly, Primary Reaction Control System thruster burns were requested at particular times during four separate growth runs. This allowed us to monitor the response Seebeck response under well-characterized growth conditions. In addition, we carried out simulations during the experiment in order to interpret the Seebeck signal. Preliminary results are described here.

Alexander J. Iwan D. (Principal Investigator)

1996-01-01

117

Effects of yttrium doping on the thermoelectric properties of Hf0.6Zr0.4NiSn0.98Sb0.02 half-Heusler alloys  

NASA Astrophysics Data System (ADS)

The (Y,Sb) codoped (Hf0.6Zr0.4)1-xYxNiSn0.98Sb0.02 (x=0, 0.01, 0.015, 0.02, and 0.025) half-Heusler alloys were prepared by levitation melting and spark plasma sintering. The effects of Y doping on the electrical conductivity, the Seebeck coefficient, and the thermal conductivity have been investigated in the temperature range of 300-900 K. It was found that the Y doping decreased the carrier concentration and electrical conductivity due to the introduction of hole carriers. The thermal conductivity was also reduced upon Y doping, mainly due to the reduced carrier thermal conductivity. The Y-doping substantially increased the Seebeck coefficient because of the decrease in carrier concentration. Pisarenko plot showed that the measured room temperature Seebeck coefficients agrees well with the predicted single parabolic band behavior as a function of the carrier concentration, suggesting that no additional mechanisms cause the extra enhancement of Seebeck coefficient in the Y-Sb codoped half-Heusler alloys. The figure of merit ZT of 1% Y-doped sample was increased by a factor of about 25% than that of the undoped sample.

Zhu, T. J.; Xiao, K.; Yu, C.; Shen, J. J.; Yang, S. H.; Zhou, A. J.; Zhao, X. B.; He, J.

2010-08-01

118

Compensation of voltage drops in solid-state switches used with thermoelectric generators  

NASA Technical Reports Server (NTRS)

Seebeck effect solid state switch was developed eliminating thermoelectric generator switch voltage drops. Semiconductor switches were fabricated from materials with large Seebeck coefficients, arranged such that Seebeck potential is generated with such polarity that current flow is aided.

Shimada, K.

1972-01-01

119

Transverse thermoelectric effects in platinum strips on permalloy films  

NASA Astrophysics Data System (ADS)

A comprehensive study on thermoelectric effects is performed for the transverse Pt strips attached to a longitudinal permalloy (Py) layer or sandwiched between two longitudinal Py layers. Thermal voltages jointly determined by planar Nernst effect (PNE), anomalous Nernst effect (ANE), and spin Seebeck effect (SSE) are detected across the Pt strip when a thermal gradient exists. By comparing the data of two differently structured samples, the respective contributions of the PNE, ANE, and SSE to thermal voltage are determined, and they have the ratio of 64:26:10, without considering the shunting effect of conductive Py, or 35:15:50, after the shunting-effect correction.

Wang, S. H.; Zou, L. K.; Cai, J. W.; Shen, B. G.; Sun, J. R.

2013-12-01

120

Observation of the planar Nernst effect in permalloy and nickel thin films with in-plane thermal gradients.  

PubMed

We present experimental evidence of a transverse thermopower, or planar Nernst effect, in ferromagnetic metal thin films driven by thermal gradients applied in the plane of the films. Samples of 20 nm thick Ni and Ni(80)Fe(20) were deposited on 500 nm thick suspended Si-N thermal isolation platforms with integrated platinum strips designed originally to allow measurement of thermally generated spin currents (the spin Seebeck effect). The low thermal conductivity of the thin supporting Si-N structure results in an essentially 2D geometry that approaches the zero substrate limit, dramatically reducing the contribution of thermal gradients perpendicular to the sample plane typically found in similar experiments on bulk substrates. The voltage on the platinum strips generated transverse to the applied thermal gradient (V(T)) is linear with increasing ?T and exhibits a sign reversal on hot and cold sides of the sample. However, V(T) is always even in applied magnetic field and shows a sin? cos? angular dependence, both key indicators of the planar Nernst effect. Within the 5 nV estimated error of our experiment there is no evidence of a signal from the spin Seebeck effect, which would have cos? angular dependence, suggesting a reduced spin Seebeck coefficient in a planar, entirely thin-film geometry. PMID:23215412

Avery, A D; Pufall, M R; Zink, B L

2012-11-01

121

Observation of the Planar Nernst Effect in Permalloy and Nickel Thin Films with In-Plane Thermal Gradients  

NASA Astrophysics Data System (ADS)

We present experimental evidence of a transverse thermopower, or planar Nernst effect, in ferromagnetic metal thin films driven by thermal gradients applied in the plane of the films. Samples of 20 nm thick Ni and Ni80Fe20 were deposited on 500 nm thick suspended Si-N thermal isolation platforms with integrated platinum strips designed originally to allow measurement of thermally generated spin currents (the spin Seebeck effect). The low thermal conductivity of the thin supporting Si-N structure results in an essentially 2D geometry that approaches the zero substrate limit, dramatically reducing the contribution of thermal gradients perpendicular to the sample plane typically found in similar experiments on bulk substrates. The voltage on the platinum strips generated transverse to the applied thermal gradient (VT) is linear with increasing ?T and exhibits a sign reversal on hot and cold sides of the sample. However, VT is always even in applied magnetic field and shows a sin??cos?? angular dependence, both key indicators of the planar Nernst effect. Within the 5 nV estimated error of our experiment there is no evidence of a signal from the spin Seebeck effect, which would have cos?? angular dependence, suggesting a reduced spin Seebeck coefficient in a planar, entirely thin-film geometry.

Avery, A. D.; Pufall, M. R.; Zink, B. L.

2012-11-01

122

Colossal enhancement in thermoelectric effect in a laterally coupled double-quantum-dot chain by the Coulomb interactions  

NASA Astrophysics Data System (ADS)

Thermoelectric effects, including Seebeck coefficient (S), thermal conductance (?), and figure of merit (ZT), in a laterally coupled double-quantum-dot (DQD) chain with two external nonmagnetic contacts are investigated theoretically by the nonequilibrium Green's function formalism. In this system, the DQD chain between two contacts forms a main channel for thermal electrons transporting, and each QD in the main chain couples laterally to a dangling one. The numerical calculations show that the Coulomb interactions not only lead to the splitting of the asymmetrical double-peak structure of the Seebeck coefficient, but also make the thermal spectrum show a strong violation of the Wiedemann–Franz law, leading to a colossal enhancement in ZT. These results indicate that the coupled DQD chain has potential applications in the thermoelectric devices with high thermal efficiency.

Xiong, Lun; Yi, Lin

2014-04-01

123

Synthetic conditions and their doping effect on {Beta}-K{sub 2}Bi{sub 8}Se{sub 13}.  

SciTech Connect

In this work the synthetic conditions for K{sub 2}Bi{sub 8}Se{sub 13} and their effect on its thermoelectric properties were investigated. K{sub 2}Bi{sub 8}Se{sub 13} was prepared as a single phase using K{sub 2}Se and Bi{sub 2}Se{sub 3} as starting materials in a furnace or via a reaction using direct flame, followed by remelting or annealing. Seebeck coefficient measurements showed that the doping level in the material is sensitive to the synthetic conditions. Higher synthesis temperatures as well as the flame reaction technique followed by annealing gave more homogenous samples with higher Seebeck coefficient. IR optical spectroscopic measurements showed a wide range of doping level achieved among the different synthetic conditions. These findings suggest that synthetic conditions can act as a useful tool for the optimization of the thermoelectric properties of these materials.

Kyratsi, Th.; Kika, I.; Hatzikraniotis, E.; Paraskevopoulos, K. M.; Chrissafis, K.; Kanatzidis, M. G. (Materials Science Division); (Univ. Cyprus); (Aristotle Univ. Thessaloniki); (Northwestern Univ.)

2009-04-01

124

Effect of Deposition Conditions on the Microstructure and the Thermoelectric Properties of Galvanostatically Electrodeposited Bi2Te3 Film  

NASA Astrophysics Data System (ADS)

Bismuth Telluride (Bi2Te3) films were deposited by a simple and cost-effective galvanostatic electrodeposition process from a solution containing bismuth tri-nitrate penta-hydrate and tellurium dioxide of different concentration ratios in 1 M nitric acid onto gold sputtered silicon substrate at various current densities. The effect of distinct current densities, electrolyte concentrations and electrodes distances on the microstructure and the thermoelectric properties of Bi2Te3 films were investigated. X-Ray diffraction (XRD) and field emission scanning electron microscope (FESEM) analysis ensured a high density, homogenous and near stoichiometric film. The surface morphology, crystalline structure and grain size were correlated with the applied current density. A prominent orientation (110) was observed for all the films and the grain size was acquired from 21 to 45 nm. The Seebeck measurement affirmed n-type semiconductor behavior of the deposited films. Enhancement in carrier mobility without significant change of the carrier concentration and Seebeck coefficient was achieved by tuning the electrodes distance. The thermoelectric film has a maximum measured Seebeck coefficient of -61.215 ?V/K and a very high electrical conductivity of 2.13 × 103 ?-1 ? cmn-1. The maximum calculated power factor was 8.2 ?W?K-2 ? cm-1.

Rashid, Mohammad Mamunur; Chung, Gwiy-Sang

2013-10-01

125

Influence of electron scatterings on thermoelectric effect  

NASA Astrophysics Data System (ADS)

In this work, we employed non-equilibrium Green's function to investigate the electron transport properties in a nanowire in the presence of scatterings. The scattering mechanism is modelled by the Büttiker probe. The effect of electron scattering is analyzed under three conditions: absence of external field; with a bias voltage; and with a finite temperature difference. It is found that weak and strong scattering strengths affect the electron transport in different ways. In the case of weak scattering strength, electron trapping increases the electron density, thereby boosting the conductance significantly. Although the increment in conductance would reduce the Seebeck coefficient slightly, the power factor still increases. In the case of strong scattering strength, electron diffraction causes the redistribution of electrons; accumulation of electrons at the ends of the wire blocks current flow; hence the conductance is reduced significantly. Although the Seebeck coefficient increases slightly, the power factor still decreases. The power factor is enhanced by 6%-18%, at the optimum scattering strength.

Li, Jing; Cheung Au Yeung, Tin; Hin Kam, Chan

2012-08-01

126

Effects of point defects on thermal and thermoelectric properties of InN  

NASA Astrophysics Data System (ADS)

In contrast to most semiconductors, electrical conductivity of InN is known to increase upon high-energy particle irradiation. The effects of irradiation on its thermal and thermoelectric properties have yet to be investigated. Here we report the thermal conductivity of high-quality InN to be 120 W/m K and examine the effects of point defects generated by irradiation on the thermal conductivity and Seebeck coefficient. We show that irradiation can be used to modulate the thermal and thermoelectric properties of InN by controlling point defect concentrations. The thermoelectric figure of merit of InN was found to be insensitive to irradiation.

Levander, A. X.; Tong, T.; Yu, K. M.; Suh, J.; Fu, D.; Zhang, R.; Lu, H.; Schaff, W. J.; Dubon, O.; Walukiewicz, W.; Cahill, D. G.; Wu, J.

2011-01-01

127

Effect of hot-press sintering temperature on thermal transport properties of TiSe2  

NASA Astrophysics Data System (ADS)

Titanium diselenide (TiSe2) alloy was prepared using solid state reaction method and hot press sintering. The effects of hot press sintering temperatures on TiSe2 were studied on the thermal transport properties of the material. As grown material shows pure TiSe2 phase and layer structure. Increasing sintering temperature results in reduced electrical resistivity ? whereas the Seebeck coefficient, ? show no significant relative change. Reduced electrical resistivity may be attributed to the increased crystalline nature. This results in improved power factor showing the optimum condition for producing better TiSe2 thermoelectric material.

Bhatt, R.; Bhattacharya, S.; Basu, R.; Patel, M.; Singh, A.; Bhatt, P.; Aswal, D. K.; Gupta, S. K.

2013-06-01

128

Rapid thermal annealing effects on the microstructure and the thermoelectric properties of electrodeposited Bi2Te3 film  

NASA Astrophysics Data System (ADS)

Bismuth telluride thermoelectric films were prepared by galvanostatic process from 1 M nitric acid solution containing 8 mM Bi3+ and 8 mM HTeO2+. Both the n and p-type films were deposited. The thermoelectric properties of the films were measured before and after the rapid thermal annealing treatment to observe the annealing effects on the as-deposited film. Post annealing treatment was carried out under Ar environment at 200-300 °C for 2-10 min duration. Annealing effects on microstructure were examined from X-Ray diffraction (XRD) patterns and Scanning Electron Microscopy images. Electrical transport properties were analyzed by Hall Effect measurement system. The analysis revealed that the carrier density decreased and the carrier mobility increased with the enhancing of annealing temperature and duration. The Seebeck coefficient and power factor were improved significantly after rapid annealing treatment for both n and p-type Bi2Te3 films. For n-type Bi2Te3 film, the Seebeck coefficient improved about three-fold (from -57 to -169.49 ?V/K) and the power factor improved around six-fold (from 2.74 to 17.37 ?W/K2 cm) after annealing. On the other hand, for p-type Bi2Te3 film the Seebeck coefficient enhanced around three-fold (from 28 to 112.3 ?V/K) and the power factor enhanced around two-fold (from 2.57 to 4.43 ?W/K2 cm) after annealing.

Rashid, Mohammad Mamunur; Cho, Kyung Ho; Chung, Gwiy-Sang

2013-08-01

129

Specific salt effects on thermophoresis of charged colloids.  

PubMed

We study the Soret effect of charged polystyrene particles as a function of temperature and electrolyte composition. As a main result we find that the Soret coefficient is determined by charge effects, and that non-ionic contributions are small. In view of the well-known electric-double layer interactions, our thermal field-flow fractionation data lead us to the conclusion that the Soret effect originates to a large extent from diffusiophoresis in the salt gradient and from the electrolyte Seebeck effect, both of which show strong specific-ion effects. Moreover, we find that thermophoresis of polystyrene beads is fundamentally different from proteins and aqueous polymer solutions, which show a strong non-ionic contribution. PMID:24652409

Eslahian, Kyriakos A; Majee, Arghya; Maskos, Michael; Würger, Alois

2014-03-28

130

A Quantitative Model for the Thermocouple Effect Using Statistical and Quantum Mechanics  

NASA Astrophysics Data System (ADS)

This paper employs statistical and quantum mechanics to develop a model for the mechanism underlying the Seebeck effect. The conventional view of the equilibrium criterion for valence electrons in a material is that the Fermi Energy should be constant throughout the system. However, this criterion is an approximation and it is shown to be inadequate for thermocouple systems. An improved equilibrium criterion is developed by applying statistical and quantum mechanics to determine the total flow of electrons across an arbitrary boundary within a system. Dynamic equilibrium is then considered to be the situation where the Fermi Energy either side of the boundary is such that the flow of electrons in each direction is the same. This equilibrium criterion is then applied to the conditions along the thermocouple wires and at the junctions in order to generate a model for the Seebeck effect. The equations involved for calculating the electronic structure of a material cannot be solved analytically, so a solution is achieved using numeric models employing CASTEP code running on a Sun Beowulf cluster and iterative algorithms written in the Excel™ VBA language on a PC. The model is used to calculate the EMF versus temperature function for the gold versus platinum thermocouple, which is then compared with established experimental data.

Bramley, Paul; Clark, Stewart

2003-09-01

131

Thermal Cycling Effects on the Thermoelectric Properties of n-Type In, Ce based Skutterudite Compounds  

SciTech Connect

N-type In-filled CoSb3 are known skutterudite compounds that have shown promising thermoelectric (TE) properties resulting in high dimensionless figure of merit values at elevated temperatures. Their use in various waste heat recovery applications will require that they survive and operate after exposure to harsh thermal cycling environments. This research focused on uncovering the thermal cycling effects on thermoelectric properties of n-type In0.2Co4Sb12 and In0.2Ce0.15Co4Sb12 skutterudite compositions as well as quantifying their temperature-dependent structural properties (elastic modulus, shear modulus, and Poisson's ratio). It was observed that the Seebeck coefficient and resistivity increased only slightly in the double-filled In,Ce skutterudite materials upon thermal cycling. In the In-filled skutterudites the Seebeck coefficient remained approximately the same on thermal cycling, while electrical resistivity increased significantly after thermal cycling. Results also show that thermal conductivity marginally decreases in the case of In-filled skutterudites, whereas the reduction is more pronounced in In, Ce-based skutterudite compounds. The possible reason for this kind of reduction can be attributed to grain pinning effects due to formation of nano inclusions. High temperature structural property measurements (i.e., Young's modulus and shear modulus) are also reported and the results show that these structural properties decrease slowly as temperature increases and the compounds are structurally stable after numerous thermal cycles.

Biswas, Krishnendu; Subramanian, Mas A.; Good, Morris S.; Roberts, Kamandi C.; Hendricks, Terry J.

2012-06-14

132

Temperature and size effects on electrical properties and thermoelectric power of Bismuth Telluride thin films deposited by co-sputtering  

NASA Astrophysics Data System (ADS)

N-type Bismuth telluride thin films of different thicknesses were deposited on cleaned glass substrate at room temperature by co-sputtering technique. The films were annealed at 300 °C for 12 h in nitrogen atmosphere to improve their properties. The thermoelectric power and electrical properties measurements were carried out on the films with thickness from 70 nm to 480 nm in the temperature range 300-430 K. The thickness dependence of electrical resistivity and Seebeck coefficient of annealed films was analyzed using the effective mean free path model. Some physical parameters such as effective mean free path of charge carriers in hypothetical bulk, the exponent of the energy term of mean free path, activation energy, and the Fermi energy were calculated. Both the electrical conductivity and the Seebeck coefficient of the bismuth telluride films increased with increasing of film thickness and grain size. Films with fewer grain boundaries and defects have longer effective mean free path of carriers and the mean free path decreases with the increase of temperature. The electron-phonon interaction was considered as the main scattering mechanism in the annealed bismuth telluride thin films.

Zeng, Zhigang; Yang, Penghui; Hu, Zhiyu

2013-03-01

133

Hall effect measurements on epitaxial SmNiO3 thin films and implications for antiferromagnetism  

NASA Astrophysics Data System (ADS)

The rare-earth nickelates (RNiO3) exhibit interesting phenomena such as unusual antiferromagnetic order at wave vector q = (½, 0, ½) and a tunable insulator-metal transition that are subjects of active research. Here we present temperature-dependent transport measurements of the resistivity, magnetoresistance, Seebeck coefficient, and Hall coefficient (RH) of epitaxial SmNiO3 thin films with varying oxygen stoichiometry. We find that from room temperature through the high temperature insulator-metal transition, the Hall coefficient is holelike and the Seebeck coefficient is electronlike. At low temperature the Néel transition induces a crossover in the sign of RH to electronlike, similar to the effects of spin density wave formation in metallic systems but here arising in an insulating phase ˜200 K below the insulator-metal transition. We propose that antiferromagnetism can be stabilized by band structure even in insulating phases of correlated oxides, such as RNiO3, that fall between the limits of strong and weak electron correlation.

Ha, Sieu D.; Jaramillo, R.; Silevitch, D. M.; Schoofs, Frank; Kerman, Kian; Baniecki, John D.; Ramanathan, Shriram

2013-03-01

134

Thermosize Effects of Ideal Fermi Gases Confined in Micro/Nano-Scale Tubes  

NASA Astrophysics Data System (ADS)

It is found that when two micro/nano-scale tubes of different areas of cross sections filled with identical Fermi gas are connected to each other and the two junctions are kept at different temperatures, the finite-size effect will result in the "thermosize effects", which are analogous to thermoelectric effects in conductors and/or semiconductors. Expressions for the important parameters related to the thermosize effects, including the Seebeck-like chemical potential difference, Peltier-like heat, and Thomson-like heat, are derived in the cases of both strong degeneracy and non-degeneracy. It may be expected that there will be some novel practical applications for these thermosize effects.

Su, Guozhen; Chen, Liwei; Lin, Tongling; Chen, Jincan

2011-06-01

135

Giant thermoelectric effects in a proximity-coupled superconductor–ferromagnet device  

NASA Astrophysics Data System (ADS)

The usually negligibly small thermoelectric effects in superconducting heterostructures can be boosted dramatically due to the simultaneous effect of spin splitting and spin filtering. Building on an idea of our earlier work (Machon et al 2013 Phys. Rev. Lett. 110 047002), we propose realistic mesoscopic setups to observe thermoelectric effects in superconductor heterostructures with ferromagnetic interfaces or terminals. We focus on the Seebeck effect being a direct measure of the local thermoelectric response and find that a thermopower of the order of \\sim 250 \\mu V\\;{{K}^{-1}} can be achieved in a transistor-like structure. A measurement of the thermopower can furthermore be used to determine quantitatively the spin-dependent interface parameters that induce the spin splitting. For applications in nanoscale cooling we discuss the figure of merit for which we find values exceeding 1.5 for temperatures \\lesssim 1 K.

Machon, P.; Eschrig, M.; Belzig, W.

2014-07-01

136

Large inverse spin Hall effect in the antiferromagnetic metal Ir20Mn80  

NASA Astrophysics Data System (ADS)

A spin current is usually detected by converting it into a charge current through the inverse spin Hall effect (ISHE) in thin layers of a nonmagnetic metal with large spin-orbit coupling, such as Pt, Pd, and Ta. Here we demonstrate that Ir20Mn80, a high-temperature antiferromagnetic metal that is commonly employed in spin-valve devices, exhibits a large inverse spin Hall effect, as recently predicted theoretically. We present results of experiments in which the spin currents are generated either by microwave spin pumping or by the spin Seebeck effect in bilayers of singe-crystal yttrium iron garnet (YIG)/Ir20Mn80 and compare them with measurements in YIG/Pt bilayers. The results of both measurements are consistent, showing that Ir20Mn80 has a spin Hall angle similar to Pt, and that it is an efficient spin-current detector.

Mendes, J. B. S.; Cunha, R. O.; Alves Santos, O.; Ribeiro, P. R. T.; Machado, F. L. A.; Rodríguez-Suárez, R. L.; Azevedo, A.; Rezende, S. M.

2014-04-01

137

Effect of Ca doping level on the laser-induced voltages in tilted La1- x Ca x MnO3 (0.1 ? x ? 0.7) thin films  

NASA Astrophysics Data System (ADS)

Tilted La1- x Ca x MnO3 (0.1 ? x ? 0.7) thin films have been grown on vicinal cut LaAlO3 (100) substrate by pulsed laser deposition. The laser-induced voltage effect was studied at room temperature with the KrF excimer laser using as the thermal source. The relationships between Ca doping level and voltage signal, response time and anisotropy Seebeck coefficient were established. The voltage signal and anisotropy Seebeck coefficient increase at first with increasing Ca doping level, reach a maximum at the same Ca content around x = 0.5, and then decrease. The respond time decreases with the Ca concentration increasing, and changes very little after x = 0.5. The figure of merit F m was also the largest at this doping level, indicating a potential good performance of the photodetector devices. The variation of intrinsic structural and transport anisotropy induced by the change of Ca concentration has been proposed to account for the different LIV effects observed in LCMO thin films.

Ma, Ji; Theingi, Mya; Zhang, Hui; Chen, Qingming; Liu, Xiang

2014-03-01

138

Comment on "Unexpected size effect in the thermopower of thin-film stripes" [J. Appl. Phys. 110, 083709 (2011)  

NASA Astrophysics Data System (ADS)

In a recent article, Sun et al. [J. Appl. Phys. 110, 083709 (2011)] claim to measure a size-dependent thermoelectric effect in a micron-scale single-metal thermocouple. In this Comment, we demonstrate that the observed phenomenon is not due to a size-dependent Seebeck effect as claimed, but is rather wire-size-dependent heat transport that causes unequal heating at the bonding pads. As a result, the bonding pads are at two different temperatures, and the observed voltage corresponds to a thermoelectric effect of a parasitic thermocouple formed between their metal structure and the bonding-pad wires. We provide simulations and suggest a control experiment based on their structure that supports our contention that the observation depends on width-dependent heat transport in the wires.

Szakmany, Gergo P.; Orlov, Alexei O.; Bernstein, Gary H.; Porod, Wolfgang

2014-06-01

139

Spin-caloric transport properties of cobalt nanostructures: Spin disorder effects from first principles  

NASA Astrophysics Data System (ADS)

The fundamental aspects of spin-dependent transport processes and their interplay with temperature gradients, as given by the spin Seebeck coefficient, are still largely unexplored and a multitude of contributing factors must be considered. We used density functional theory together with a Monte-Carlo-based statistical method to simulate simple nanostructures, such as Co nanowires and films embedded in a Cu host or in vacuum, and investigated the influence of spin disorder scattering on electron transport at elevated temperatures. While we show that the spin-dependent scattering of electrons due to temperature-induced disorder of the local magnetic moments contributes significantly to the resistance, thermoelectric, and spin-caloric transport coefficients, we also conclude that the actual magnitude of these effects cannot be predicted, quantitatively or qualitatively, without such detailed calculations.

Ková?ik, Roman; Mavropoulos, Phivos; Wortmann, Daniel; Blügel, Stefan

2014-04-01

140

Effect of Bismuth Nanotubes on the Thermoelectric Properties of BiSb Alloy Nanocomposites  

NASA Astrophysics Data System (ADS)

Bismuth nanotubes have been synthesized and successfully included in Bi1- x Sb x nanoalloys to form composite structures. The nanotubes were synthesized by transformation of a ?-BiI precursor with n-BuLi solution leading to tubular bismuth structures. The Bi1- x Sb x nanoalloys were produced by ball milling. Three series of composite structures were synthesized by including different fractions (0 wt.%, 3 wt.%, 5 wt.%) of nanotubes in nanoalloys of different composition x. Investigation of thermoelectric and structural properties revealed a decrease of the thermal conductivity of up to 40% for the composites in comparison with alloys without nanotube inclusions. This effect can be attributed to enhanced phonon scattering. Seebeck coefficients and electrical conductivities were both slightly enhanced in the composite series with 3 wt.% nanotube inclusions, leading to enhancement of throughout the series compared with the nanoalloy series without nanotube inclusions.

Güne?, Ekrem; Landschreiber, Bernadette; Hartung, David; Elm, Matthias T.; Rohner, Christian; Klar, Peter J.; Schlecht, Sabine

2014-06-01

141

Al insertion and additive effects on the thermoelectric properties of yttrium boride  

NASA Astrophysics Data System (ADS)

The aluminoboride YxAlyB14 (x ˜ 0.57, 0.41 ? y ? 0.63) has been found to show striking p-n control of the thermoelectric properties through variations of the y occupancy of the Al site. The effect of Al was investigated in further extremes. Polycrystalline samples of Al-free YxB14(x ˜ 0.55; "YB25") were successfully synthesized in sufficient amounts for bulk spark plasma sintering (SPS) samples and their thermoelectric properties were investigated. Y0.56Al0.57B14 was also prepared in comparison, and further Al was added to the samples through SPS treatment. We observed that Y0.55B14 exhibits large positive Seebeck coefficients, ˜1000 ?V K-1, around room temperature and the absolute value of the Seebeck coefficient largely decreases with increase of temperature while that of Y0.56Al0.57B14 is proportional to T-1/2, indicating a strong effect of Al on the electronic structure around the Fermi level. Y0.55B14 was found to be strongly disordered with a relatively low thermal conductivity and short localization length of 0.65 Å which is close to that previously determined for the disordered and thermally glass-like compound YB66. Occupancy of Al could not be increased further for the Al-rich sample, although Al was discovered to act as a sintering aid to enhance density and ZT could be significantly improved by 50%.

Maruyama, Satofumi; Prytuliak, Anastasiia; Miyazaki, Yuzuru; Hayashi, Kei; Kajitani, Tsuyoshi; Mori, Takao

2014-03-01

142

Effect of Bi-doping and Mg-excess on the thermoelectric properties of Mg2Si materials  

NASA Astrophysics Data System (ADS)

In this work, Bi-doped magnesium silicide compounds were prepared by applying a combination of both, short-time ball milling and heating treatment. The effect of Mg excess was also studied, aiming towards further improvement in thermoelectric properties. The structural modifications of all materials were followed by Powder X-ray diffraction and Scanning Electron Microscopy. Highly dense pellets of Mg2Si1-xBix (0?x?0.035) and Mg2+?Si0.975Bi0.025 (?=0.04, 0.06 and 0.12) were fabricated via hot pressing and studied in terms of Seebeck coefficient, electrical and thermal conductivities and free carrier concentration. Their thermoelectric performance, at high temperature range, is presented and the maximum value of the dimensionless-figure-of-merit (ZT) is found to be 0.68 at 810 K, for Mg2Si0.97Bi0.03.

Ioannou, M.; Polymeris, G. S.; Hatzikraniotis, E.; Paraskevopoulos, K. M.; Kyratsi, Th.

2014-08-01

143

The great improvement effect of pores on ZT in Co1-xNixSb3 system  

NASA Astrophysics Data System (ADS)

In this paper, the Co1-xNixSb3+y system (x=0.1,0.2; y=0, 0.05) has been prepared by direct current induced hot press and annealing. Pores were made by annealing pressed Co1-xNixSb3.05 pellets into Co1-xNixSb3 pellets during annealing. It was found that from room temperature to 500 °C, the pores with diameter larger than 1 ?m has significantly increased the Seebeck coefficient, considerably decreased the thermal conductivity, almost maintained the electrical conductivity constant, and therefore markedly improved the dimensionless figure of merit (ZT) of Co1-xNixSb3 system. By comparing the samples, we conclude that inducing pores into skutterudites is an effective route to greatly improve the ZT.

He, Qinyu; Hu, Shejun; Tang, Xingui; Lan, Yucheng; Yang, Jian; Wang, Xiaowei; Ren, Zhifeng; Hao, Qing; Chen, Gang

2008-07-01

144

Effects of Nano-?-Al2O3 Dispersion on the Thermoelectric and Mechanical Properties of CoSb3 Composites  

NASA Astrophysics Data System (ADS)

Nano-?-Al2O3/CoSb3 composites with different ?-Al2O3 contents were prepared by spark plasma sintering. The effects of ?-Al2O3 addition on the microstructure, the thermoelectric properties, and the mechanical properties were studied in this article. It is found that ?-Al2O3 nanoparticles locate mainly at grain boundaries of the matrix. The dispersed particles decrease both the electrical conductivity and the thermal conductivity, but make the Seebeck coefficient increase. The dimensionless figure of merit is nearly unchanged by the dispersion. However, the introduction of nano-?-Al2O3 is very effective in improving the mechanical performance of the composites. The compressive strength and flexural strength of the 1.0 wt.% nano-?-Al2O3 dispersed samples are improved by 42.7 and 52.0%, respectively, compared with the nondispersed samples.

Wen, Pengfei; Mei, Hong; Zhai, Pengcheng; Duan, Bo

2013-11-01

145

Transport Magnetic Proximity Effects in Platinum  

NASA Astrophysics Data System (ADS)

Platinum (Pt) metal, being non-magnetic and having a strong spin-orbit coupling interaction, has been central in detecting pure spin current and establishing most of the recent spin-based phenomena. Thus, it is important to ascertain the transport and magnetic characteristics of thin Pt films in contact with a ferromagnet. In this work, we use both electric and thermal means to conclusively show the transport magnetic proximity effects (MPE) of thin Pt film in contact with ferromagnetic insulator YIG. At thicknesses comparable to, and less than, the spin diffusion length, the strong ferromagnetic characteristics in Pt films on YIG are indistinguishable from those of ferromagnetic permalloy on YIG. [1] The MPE occurs at the interface and decreases exponentially away from the interface, concentrating in only a few monolayers. As a result, the pure spin current detected by a thin Pt is tainted with a spin polarized current. The pure spin current phenomena, such as the inverse spin Hall effect and the spin Seebeck effect, have been contaminated with the anomalous Hall effect and the anomalous Nernst effect respectively. These results raise serious questions about the suitability, and the validity, of using Pt in establishing pure spin current phenomena; on the other hand, a much stronger spin-based effect can be induced by the MPE at the interface. This research is in collaboration with X. Fin, Y. P. Chen, J. Wu, and J. Q. Xiao (University of Delaware), T. Y. Chen (Arizona State University) and D. Qu, W. G. Wang, and C. L. Chien (The Johns Hopkins University).[4pt] [1] S. Y. Huang et al., Phys. Rev. Letts. 109, 107204 (2012).

Huang, Ssu-Yen

2013-03-01

146

Effects of Pd substitution on the thermoelectric and electronic properties of delafossite Cu1-xPdxFeO2 (x=0.01, 0.03 and 0.05)  

NASA Astrophysics Data System (ADS)

Cu(1-x)Pd(x)FeO2 (x=0.01, 0.03 and 005) delafossite was prepared by solid state reactions and was calcined/sintered at 1050 °C. The effect of Pd2+ substitution for the Cu1+ sites on the thermoelectric and electronic properties of Cu(1-x)Pd(x)FeO2 were investigated. The crystal structure, oxygen decomposition, thermoelectric and electronic properties were characterized by X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy (XPS), Seebeck coefficient, electrical conductivity and thermal conductivity measurements. The characterization showed that Cu(1-x)Pd(x)FeO2 formed a hexagonal delafossite structure with R3-m symmetry. The existence of Pd2+, Cu1+, Cu2+, Fe3+, Fe4+ and O was revealed from the XPS results. Confirmation of Pd2+ substitution for the Cu1+ sites occurred by increasing the c-axis in the lattice parameter with a Pd content. The O content intercalated at the center of the triangular Cu acted as a support to produce Cu2+ ions and was reduced with an increasing Pd content. The mixed valencies of Cu1+/Cu2+ and Cu1+/Pd2+ in the Cu layer changed the electrical conductivity and the Fe3+/Fe4+ mixed valencies in the FeO6 layer caused the Seebeck coefficient to increase. Both the electrical conductivity and Seebeck coefficient for Pd contents of x=0.01 and 0.03 were higher than that of non-doped CuFeO2. The low thermal conductivity of Cu(1-x)Pd(x)FeO2 resulted from the substitution of Pd, which has a large atomic mass, into structure. The Jonker plot indicated that the electronic properties displayed a degenerate density of states and that Cu(1-x)Pd(x)FeO2 was a semiconductor. A high ZT value of 0.055 was obtained for a Pd content of 0.03 at 950 K. The Pd2+ substitution for the Cu1+ sites influenced the thermoelectric and electronic properties of the delafossite Cu(1-x)Pd(x)FeO2 samples.

Ruttanapun, Chesta

2014-07-01

147

Thermomagnonic spin transfer and Peltier effects in insulating magnets  

NASA Astrophysics Data System (ADS)

The recent discovery of the spin Seebeck effect [1] in metals, insulators and semiconductors stimulated development of spincaloritronics [2]. The possibility of measuring the Onsager reciprocal spin Peltier effect has been investigated recently as well. In our theoretical work [3], we study the fictitious electromagnetic fields induced by magnetic textures which may offer an alternative route for observing the spin Peltier effect. Particularly, in an insulating ferromagnet a moving magnetic texture should effectively drive the spin (wave) current which in turn should lead to the heat current by the spin Peltier effect. We further study the coupled magnon energy transport and collective magnetization dynamics in ferromagnets with magnetic textures. We conclude that the analogy between the fictitious electromagnetic fields and real fields should lead to magnonic counterparts of such effects as the Hall effect, the Ettingshausen effect, the Nernst effect, and the Righi-Leduc effect. By constructing a phenomenological theory based on irreversible thermodynamics, we describe motion of domain walls by thermal gradients and generation of heat flows by magnetization dynamics. From microscopic description based on magnon kinetics, we estimate the transport coefficients and analyze the feasibility of energy-related applications (e.g. nanoscale heat pumps [4]) in insulating ferromagnets, such as yttrium iron garnet and europium oxide. Our estimates show that the viscous coupling effects between magnetization dynamics and magnon flows can be strong in materials with low spin densities (e.g. dilute magnetic systems) and narrow domain walls, which can allow the magnonic manipulation of magnetization dynamics and heat pumping.[4pt] [1] K. Uchida et al. Nature 455, 778 (2008).[0pt] [2] G. E. W. Bauer, A. H. MacDonald, S. Maekawa, Solid State Commun. 150, 459 (2010).[0pt] [3] A. A. Kovalev and Y. Tserkovnayk, arXiv:1106.3135.[0pt] [4] A. A. Kovalev and Y. Tserkovnyak, Solid State Commun. 150, 500 (2010).

Kovalev, Alexey A.

2012-02-01

148

Proximity effect on spin-dependent conductance and thermopower of correlated quantum dots  

NASA Astrophysics Data System (ADS)

We study the electric and thermoelectric transport properties of correlated quantum dots coupled to two ferromagnetic leads and one superconducting electrode. Transport through such hybrid devices depends on the interplay of ferromagnetic-contact-induced exchange field, superconducting proximity effect, and correlations leading to the Kondo effect. We consider the limit of large superconducting gap. The system can be then modeled by an effective Hamiltonian with a particle-nonconserving term describing the creation and annihilation of Cooper pairs. By means of the full density-matrix numerical renormalization group method, we analyze the behavior of electrical and thermal conductances, as well as the Seebeck coefficient as a function of temperature, dot level position, and strength of the coupling to the superconductor. We show that the exchange field may be considerably affected by the superconducting proximity effect and is generally a function of Andreev bound-state energies. Increasing the coupling to the superconductor may raise the Kondo temperature and partially restore the exchange-field-split Kondo resonance. The competition between ferromagnetic and superconducting proximity effects is reflected in the corresponding temperature and dot level dependence of both the linear conductance and the (spin) thermopower.

Wójcik, Krzysztof P.; Weymann, Ireneusz

2014-04-01

149

Apparatus and method for measuring the Seebeck coefficient and resistivity of materials  

NASA Technical Reports Server (NTRS)

An apparatus for measuring the thermoelectric properties of materials under high pressure is described that includes a pair of force transmitting assemblies constructed of thermally and electrically conductive material positioned between the ram and anvil of a press. Each force transmitting assembly has a small diameter pressing portion for contacting a face of the sample so that the sample can be squeezed between them. Each assembly also includes a heat exchanger to maintain the sample face at a controlled temperature, and an electrical conductor to carry current generated by the sample. A sleeve of thermally and electrically insulative material closely surrounds the pressing portions of the two assemblies.

Hadek, V. (inventor)

1973-01-01

150

Large Seebeck magnetic anisotropy in thin Co films embedded in Cu determined by ab initio investigations  

NASA Astrophysics Data System (ADS)

The longitudinal thermopower of a Cu/Co/Cu trilayer system exhibits an oscillatory dependence on the thickness of the Co layer, a behavior related to the formation of quantum well states in the minority spin channel. In addition, it is found to be very sensitive to a switching between an in-plane and out-of-plane magnetization. The resulting magnetothermopower (MTP) is therefore much larger than anticipated from the conventional anisotropic magnetoresistance (AMR). Our calculations establish a direct connection between the magnitude of the MTP signal and the asymmetry of the AMR around the Fermi energy. An enhancement of MTP based on this understanding may offer the possibility of implementing an efficient spin read-out thermoelectric device based on a single ferromagnetic layer.

Popescu, Voicu; Kratzer, Peter

2013-09-01

151

Effects of partial substitution of Co by Ni on the high-temperature thermoelectric properties of TiCoSb-based half-Heusler compounds  

Microsoft Academic Search

TiCoSb-based half-Heusler compounds were prepared by solid-state reaction and their thermoelectric properties were studied. The un-doped TiCoSb compound shows n-type conduction and demonstrates high Seebeck coefficient at high temperatures. The partial substitution of Co by Ni caused great increase in electron concentration and electrical conductivity, while the Seebeck coefficient and the thermal conductivity showed little change when Ni content (x)

Min Zhou; Chude Feng; Lidong Chen; Xiangyang Huang

2005-01-01

152

Density-of-states effective mass and scattering parameter measurements by transport phenomena in thin films  

NASA Astrophysics Data System (ADS)

A novel machine has been developed to measure transport coefficients in the temperature range of 50-350 K of thin films deposited on electrically insulating substrates. The measured coefficients-resistivity, Hall, Seebeck, and Nernst-are applied to solutions of the Boltzmann transport equation to give information about the film's density-of-states effective mass, the Fermi energy level, and an energy-dependent scattering parameter. The machine is designed to eliminate or compensate for simultaneously occurring transport phenomena that would interfere with the desired measured quantity, while allowing for all four coefficients to be measured on the same sample. An average density-of-states effective mass value of 0.29+/-0.04me was measured on the transparent conductive oxide, cadmium stannate (CTO), over a carrier concentration range of 2-7×1020 cm-3. This effective mass value matched previous results obtained by optical and thermoelectric modeling. The measured scattering parameter indicates that neutral impurities or a mixture of scattering mechanisms may inhibit the transport of carriers in CTO.

Young, D. L.; Coutts, T. J.; Kaydanov, V. I.

2000-02-01

153

The role of Coulomb interaction in thermoelectric effects of an Aharonov-Bohm interferometer  

NASA Astrophysics Data System (ADS)

We investigate the thermoelectric effects of an Aharonov-Bohm (AB) interferometer with a quantum dot (QD) embedded in each of its arms, where the intra-dot Coulomb interaction between electrons in each QD is taken into account. Using Green's function methods and the equation of motion (EOM) technique, we find that the Seebeck coefficient and Lorenz number can be strongly enhanced when the chemical potential sweeps the molecular states associated with the Fano line-shapes in the transmission spectra, due to quantum interference effects between the bonding and antibonding molecular states. It is found that enhancement of the thermoelectric effects occurs between the two groups of conductance peaks in the presence of strong intra-dot Coulomb interaction—the reason being that a transmission node is developed in the Coulomb blockade regime. In this case, the maximum value of the Lorenz number approaches 10?2kB2/(3e2). Its thermoelectric conversion efficiency in the absence of phonon thermal conductance, described by the figure of merit ZT, approaches 2 at room temperature. Therefore, it may be used as a high-efficiency solid-state thermoelectric conversion device under certain circumstances.

Liu, Yu-Shen; Zhang, De-Bao; Yang, Xi-Feng; Feng, Jin-Fu

2011-06-01

154

Spin thermoelectric effects in Kondo quantum dots coupled to ferromagnetic leads  

NASA Astrophysics Data System (ADS)

Thermoelectric effects in transport through a quantum dot coupled to external ferromagnetic leads are investigated theoretically. The basic thermoelectric transport characteristics, such as thermopower, electronic contribution to the heat conductance, and the corresponding figure of merit, are calculated in the linear response regime by means of the density-matrix numerical renormalization group method. The case of a nonzero spin splitting of the electrochemical potential in the electrodes is also considered and the associated spin thermoelectric effects are analyzed. It is shown that the spin-dependent thermoelectric phenomena in the local moment regime depend generally on the exchange field induced by ferromagnetic contacts. In addition, the temperature dependence of the Seebeck coefficient is rather nontrivial, and depends on the spin polarization and spin relaxation in the leads. In the presence of ferromagnetic leads, the thermopower as a function of temperature may change sign more times than the thermopower for nonmagnetic leads. These changes can be thus used to determine the relevant Kondo behavior and Kondo energy scale in the system. Moreover, the effects of external magnetic field and different spin polarization of ferromagnetic leads are also analyzed.

Weymann, I.; Barna?, J.

2013-08-01

155

Response time measurement in flow induced signal generation on semiconductors  

Microsoft Academic Search

Measurable electrical signal is generated when a gas flows over a variety of solids, including doped semiconductors, even at the modest speed of a few meters per second. The underlying mechanism is an interesting interplay of Bernoulli's principle and the Seebeck effect. The electrical signal depends on the square of Mach number (M) and is proportional to the Seebeck coefficient

Sankha S. Sarkar; S. Ghosh; A. K. Sood

2007-01-01

156

Importance of relativistic effects in electronic structure and thermopower calculations for Mg2Si, Mg2Ge, and Mg2Sn  

NASA Astrophysics Data System (ADS)

We present a theoretical study of the influence of relativistic effects on the electronic band structure and thermopower of Mg2X (X = Si, Ge, Sn) semiconductors. The full potential Korringa-Kohn-Rostoker (KKR) method is used, and a detailed comparison between the fully relativistic and semirelativistic electronic structure features is done. We show that the spin-orbit (S-O) interaction splits the valence band at ? point in good agreement with the experimental data, and this effect strongly depends on X atom. The S-O modifications of the topology of the ?-centered holelike Fermi surface pockets lead to a change in electron transport properties, which are investigated using the Boltzmann approach. In addition, a simple and efficient method is presented for the calculation of density of states effective mass m*, and then used to examine the impact of relativistic effects on m*. It is found that the S-O coupling of the valence bands reduces the effective mass and therefore significantly lowers the thermopower, primarily in Mg2Sn, but also in Mg2Ge. A detrimental influence of the S-O interaction on the thermoelectric performance of p-type Mg2X is analyzed as a function of temperature (10-900 K) and carrier concentration (1018-1022 cm-3). Interestingly, similar calculations in n-type Mg2X, show a negligible effect of the S-O interaction on the lowest conduction bands and, consequently, also on the Seebeck coefficient.

Kutorasinski, K.; Wiendlocha, B.; Tobola, J.; Kaprzyk, S.

2014-03-01

157

Thermal Hall effect in YBCO: Probing Fermi-surface reconstruction inside the superconducting state  

NASA Astrophysics Data System (ADS)

The thermal Hall (Righi-Leduc) effect was measured in the cuprate superconductor YBCO at a doping p = 0.11, as a function of magnetic field H up to 29 T. At temperatures well below the zero-field superconducting Tc, the thermal Hall conductivity ?xy is positive at low field and then turns over to become negative at fields above 15 T. The negative ?xy is consistent with the negative Hall and Seebeck coefficients observed in the normal state above 25 T [1,2]. This further supports our interpretation: the Fermi surface of YBCO contains a small electron-like pocket [3] in that region of the phase diagram, the result of a Fermi-surface reconstruction attributed to stripe order [4]. In the T = 0 limit at H = 29 T, we find reasonable agreement with the Wiedemann-Franz law, ?xy/T=L0?xy. The fact that ?xy changes sign at H 15 T is consistent with a scenario of phase competition whereby stripe order emerges only at finite field, in agreement with recent NMR studies that detect the onset of charge-stripe order above 15 T [5]. [4pt] [1] LeBoeuf et al., PRB 83, 054056 (2011); [2] Lalibert'e et al., Nat. Commun. 2, 432 (2011); [3] LeBoeuf et al., Nature 450, 533 (2007); [4] Chang et al., PRL 104, 057005 (2010); [5] Wu et al., Nature 477, 191 (2011).

Cyr-Choinière, Olivier; Laliberté, Francis; Dufour-Beauséjour, Sophie; Grissonnanche, Gaël.; Gordon, Ryan T.; Doiron-Leyraud, Nicolas; Taillefer, Louis; Ramshaw, Brad J.; Liang, Ruixing; Bonn, Doug A.; Hardy, Walter N.; Proust, Cyril

2012-02-01

158

Effect of local atomic and electronic structures on thermoelectric properties of chemically substituted CoSi  

NASA Astrophysics Data System (ADS)

We report the effects of Ge partial substitution for Si on local atomic and electronic structures of thermoelectric materials in binary compound cobalt monosilicides (\\text{CoSi}_{1-x}\\text{Ge}_{x}\\text{:}\\ 0 \\le x \\le 0.15 ). Correlations between local atomic/electronic structure and thermoelectric properties are investigated by means of X-ray absorption spectroscopy. The spectroscopic results indicate that as Ge is partially substituted onto Si sites at x \\le 0.05 , Co in CoSi1?xGex gains a certain amount of charge in its 3d orbitals. Contrarily, upon further replacing Si with Ge at x \\ge 0.05 , the Co 3d orbitals start to lose some of their charge. Notably, thermopower is strongly correlated with charge redistribution in the Co 3d orbital, and the observed charge transfer between Ge and Co is responsible for the variation of Co 3d occupancy number. In addition to Seebeck coefficient, which can be modified by tailoring the Co 3d states, local lattice disorder may also be beneficial in enhancing the thermoelectric properties. Extended X-ray absorption fine structure spectrum results further demonstrate that the lattice phonons can be enhanced by Ge doping, which results in the formation of the disordered Co-Co pair. Improvements in the thermoelectric properties are interpreted based on the variation of local atomic and electronic structure induced by lattice distortion through chemical substitution.

Hsu, C. C.; Pao, C. W.; Chen, J. L.; Chen, C. L.; Dong, C. L.; Liu, Y. S.; Lee, J. F.; Chan, T. S.; Chang, C. L.; Kuo, Y. K.; Lue, C. S.

2014-05-01

159

Compositional disorder and its effect on the thermoelectric performance of Zn?P? nanowire-copper nanoparticle composites.  

PubMed

Recent studies indicated that nanowire format of materials is ideal for enhancing the thermoelectric performance of materials. Most of these studies were performed using individual nanowires as the test elements. It is not currently clear whether bulk assemblies of nanowires replicate this enhanced thermoelectric performance of individual nanowires. Therefore, it is imperative to understand whether enhanced thermoelectric performance exhibited by individual nanowires can be extended to bulk assemblies of nanowires. It is also imperative to know whether the addition of metal nanoparticle to semiconductor nanowires can be employed for enhancing their thermoelectric performance further. Specifically, it is important to understand the effect of microstructure and composition on the thermoelectric performance on bulk compound semiconductor nanowire-metal nanoparticle composites. In this study, bulk composites composed of mixtures of copper nanoparticles with either unfunctionalized or 1,4-benzenedithiol (BDT) functionalized Zn?P? nanowires were fabricated and analyzed for their thermoelectric performance. The results indicated that use of BDT functionalized nanowires for the fabrication of composites leads to interface-engineered composites that have uniform composition all across their cross-section. The interface engineering allows for increasing their Seebeck coefficients and electrical conductivities, relative to the Zn?P? nanowire pellets. In contrast, the use of unfunctionalized Zn?P? nanowires for the fabrication of composite leads to the formation of composites that are non-uniform in composition across their cross-section. Ultimately, the composites were found to have Zn?P? nanowires interspersed with metal alloy nanoparticles. Such non-uniform composites exhibited very high electrical conductivities, but slightly lower Seebeck coefficients, relative to Zn?P? nanowire pellets. These composites were found to show a very high zT of 0.23 at 770 K, orders of magnitude higher than either interface-engineered composites or Zn?P? nanowire pellets. The results indicate that microstructural composition of semiconductor nanowire-metal nanoparticle composites plays a major role in determining their thermoelectric performance, and such composites exhibit enhanced thermoelectric performance. PMID:24577096

Brockway, Lance; Vasiraju, Venkata; Vaddiraju, Sreeram

2014-03-28

160

Investigation of transverse Peltier effect on top-seeded melt textureYBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}  

SciTech Connect

The transverse Peltier effect is investigated on the top-seeded melt texture superconductor YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} (YBCO). By restricting the heat absorbing or evolving on one of the sample{close_quote}s surfaces, the Peltier heat flow is converted into a temperature difference for measurement. The temperature difference is found proportional to the current applied, which is in accordance with the prediction of transverse Peltier effect. Based on a simplified model, the difference of the Seebeck coefficients between the {ital ab} plane and the {ital c} axis, {vert_bar}{ital S}{sub {ital ab}}{minus}{ital S}{sub {ital c}}{vert_bar}, is about 35 {mu}V/K. It is in good agreement with that of large single crystal [I. Terasaki, Y. Sato, S. Tajima, S. Miyamoto, and S. Tanaka, Physica C {bold 235-240}, 1413 (1994)]. The transverse Peltier effect is verified. This supports the idea that the off-diagonal thermoelectric effect is responsible for the anomalously high laser-induced transient transverse voltage on the oriented YBCO superconducting thin films. {copyright} {ital 1996 American Institute of Physics.}

He, Z.H.; Ma, Z.G.; Li, Q.Y.; Luo, Y.Y.; Zhang, J.X. [Department of Physic, Zhongshan University, Guangzhou 510275, People`s Republic of (China)] [Department of Physic, Zhongshan University, Guangzhou 510275, People`s Republic of (China); Meng, R.L.; Chu, C.W. [Texas Center for Superconductivity at the University of Houston, Houston, Texas 77204-5932 (United States)] [Texas Center for Superconductivity at the University of Houston, Houston, Texas 77204-5932 (United States)

1996-12-01

161

Effect of Synthesis and Sintering Conditions on the Thermoelectric Properties of n-Doped Mg2Si  

NASA Astrophysics Data System (ADS)

Magnesium silicide (Mg2Si)-based alloys are promising candidates for thermoelectric (TE) energy conversion in the middle-high temperature range. The detrimental effect of the presence of MgO on the TE properties of Mg2Si based materials is widely known. For this reason, the conditions used for synthesis and sintering were optimized to limit oxygen contamination. The effect of Bi doping on the TE performance of dense Mg2Si materials was also investigated. Synthesis was performed by ball milling in an inert atmosphere starting from commercial Mg2Si powder and Bi powder. The samples were consolidated, by spark plasma sintering, to a density >95%. The morphology, and the composition and crystal structure of samples were characterized by field-emission scanning electronic microscopy and x-ray diffraction, respectively. Moreover, determination of Seebeck coefficients and measurement of electrical and thermal conductivity were performed for all the samples. Mg2Si with 0.1 mol% Bi doping had a ZT value of 0.81, indicative of the potential of this method for fabrication of n-type bulk material with good TE performance.

Fiameni, S.; Famengo, A.; Agresti, F.; Boldrini, S.; Battiston, S.; Saleemi, M.; Johnsson, M.; Toprak, M. S.; Fabrizio, M.

2014-02-01

162

Exploring the doping effects of Ag in p-type PbSe compounds with enhanced thermoelectric performance  

NASA Astrophysics Data System (ADS)

In this study, we prepared a series of Ag-doped PbSe bulk materials by a melting-quenching process combined with a subsequent spark plasma sintering process, and systematically investigated the doping effects of Ag on the thermoelectric properties. Ag substitution in the Pb site does not introduce resonant levels near the valence band edge or detectable change in the density of state in the vicinity of the Fermi level, but moves the Fermi level down and increases the carrier concentration to a maximum value of ~4.7 × 1019 cm-3 which is still insufficient for heavily doped PbSe compounds. Nonetheless, the non-monotonic variation in carrier concentration with increasing Ag content indicates that Ag doping reaches the solution limit at ~1.0% and the excessive Ag presumably acts as donors in the materials. Moreover, the large energy gap of the PbSe-based material wipes off significant 'roll-over' in the Seebeck coefficient at elevated temperatures which gives rise to high power factors, being comparable to p-type Te analogues. Consequently, the maximum ZT reaches ~1.0 for the 1.5% Ag-doped samples with optimized carrier density, which is ~70% improvement in comparison with an undoped sample and also superior to the commercialized p-type PbTe materials.

Wang, Shanyu; Zheng, Gang; Luo, Tingting; She, Xiaoyu; Li, Han; Tang, Xinfeng

2011-11-01

163

Effect of ruthenium substitution in layered sodium cobaltate Na xCoO 2: Synthesis, structural and physical properties  

NASA Astrophysics Data System (ADS)

Solid-state synthesis of Na 0.71Co 1-xRu xO 2 compositions shows that ruthenium can be substituted for cobalt in the hexagonal Na 0.71CoO 2 phase up to x=0.5. The cell expands continuously with increasing ruthenium content. All mixed Co-Ru phases show a Curie-Weiss behaviour with no evidence of magnetic ordering down to 2 K. Unlike the parent phase Na 0.71CoO 2, ruthenium-substituted phases are all semiconducting. They exhibit high thermoelectric power, with a maximum of 165 ?V/K at 300 K for x=0.3. The Curie constant C and Seebeck coefficient S show a non-monotonic evolution as a function of ruthenium content, demonstrating a remarkable interplay between magnetic properties and thermoelectricity. The presence of ruthenium has a detrimental effect on water intercalation and superconductivity in this system. Applying to Ru-substituted phases the oxidative intercalation of water known to lead to superconductivity in the Na xCoO 2 system yields a 2-water layer hydrate only for x=0.1, and this phase is not superconducting down to 2 K.

Strobel, Pierre; Muguerra, Hervé; Hébert, Sylvie; Pachoud, Elise; Colin, Claire; Julien, Marc-Henri

2009-07-01

164

Effects of indium-filling and synthesis pressure on the thermoelectric properties of CoSb3  

NASA Astrophysics Data System (ADS)

InxCo4Sb12 skutterudite compounds have been prepared successfully at different synthesis pressures by high pressure and high temperature (HPHT) method, the processing time has been reduced from a few days to half an hour. In addition, the effect of synthesis pressure on the thermoelectric properties of In0.4Co4Sb12 compounds has been investigated in this paper. The structure of In0.4Co4Sb12 samples was evaluated by means of X-ray diffraction and scanning electron microscopy (SEM). The Seebeck coefficient, electrical resistivity and thermal conductivity were all measured in the temperature range of room temperature to 673 K. The sample synthesized at 2.0 GPa showed the highest power factor of 29.3 ?Wcm-1K-2 at 373 K. A dimensionless thermoelectric figure of merit (ZT) of 0.51 at 673 K was achieved for n-type In0.4Co4Sb12 prepared at 1.3 GPa, which was significantly enhanced in comparison with pure CoSb3.

Deng, Le; Wang, Li Bin; Qin, Jie Ming; Zheng, Tao; Jia, Xiao Peng; Ma, Hong An

2014-06-01

165

High Performance Thermoelectric Materials Using Solution Phase Synthesis of Narrow Bandgap Core/Shell Quantum Dots Deposited Into Colloidal Crystal Thin Films.  

National Technical Information Service (NTIS)

Thermoelectrics is the science and technology associated with thermoelectric converters, that is, the generation of electrical power based on the Seebeck effect and refrigeration by the Peltier effect. The attractive features of thermoelectric devices are...

2005-01-01

166

The Effect of Annealing in Controlled Vapor Pressure on the Thermoelectric Properties of RF-Sputtered Bi2Te3 Film  

NASA Astrophysics Data System (ADS)

To investigate the effect of annealing in controlled atmosphere on the thermoelectric properties of Bi-Te film, Te-deficient Bi-Te film was deposited by sputtering, and then annealed with various Bi-Te alloy powders with different Te concentrations in a closed system at 250°C for 24 h. Bi-Te phases other than Bi2Te3 in the as-deposited film could be removed when the film was annealed with Bi-Te source powder containing 62 at.% or higher content of Te. At the same time, the values of Seebeck coefficient and carrier concentration of the films approach -105 ?V/K and 3 × 1019 cm-3 to 6 × 1019 cm-3, respectively. This result indicates that mass transport of Te to the film takes place, resulting in the formation of Bi2Te3 phase and reduction of the amount of p-type carriers due to compositional change of the film from Te-deficient to stoichiometric. Annealing in controlled Te-vapor atmosphere is an effective method to improve the thermoelectric properties of Bi-Te film by changing the composition and phase of Te-deficient film to stoichiometric Bi2Te3 film.

Kim, Hyo-Jung; Yim, Ju-Hyuk; Choi, Won Chel; Park, Chan; Kim, Jin-Sang

2012-06-01

167

Impact of interfacial resistance switching on thermoelectric effect of Nb-doped SrTiO3 single crystalline  

NASA Astrophysics Data System (ADS)

The thermoelectric properties of the bistable resistance states in Nb doped SrTiO3 single crystal have been investigated. The Seebeck coefficients for both low and high resistance states change linearly with temperature. The three-terminals contrast measurement demonstrates that a large fraction of the voltage drop is applied at the tiny volume near the bottom interface between the electrode and the oxide bulk. Therefore, the metallic oxide bulk plays a dominant role in the temperature dependence of Seebeck coefficients. The thermoelectric properties of new resistance switching (RS) devices with minimized non-RS volume could be exploited for the RS mechanism and novel applications.

Zhang, Peijian; Meng, Yang; Liu, Ziyu; Li, Dong; Su, Tao; Meng, Qingyu; Mao, Qi; Pan, Xinyu; Chen, Dongmin; Zhao, Hongwu

2012-03-01

168

Effect of temperature dependence of electrical resistivity on the cooling performance of a single thermoelectric element  

Microsoft Academic Search

The coefficients of performance (COP) ?0 and ? for a single thermoelectric (TE) element welded with two metal plates were calculated as functions of temperature difference (?T) and thermoelectric figure of merit (ZT) from the conventional thermal rate equations and the new thermal rate ones proposed here, respectively. We made an attempt to take the differences in the Seebeck coefficient

Osamu Yamashita

2008-01-01

169

Band Structure Engineering in Geometry-Modulated Nanostructures for Thermoelectric Efficiency Enhancement  

NASA Astrophysics Data System (ADS)

The energy subband structure of nanowires with periodically modulated cross-section has been calculated within a continuum model and the effective mass approximation. A characteristic structure of minibands and resonances has been found. This leads to a remarkable enhancement of the Seebeck coefficient compared with that of nonmodulated nanowires of the same dimensions. The Seebeck coefficient enhancement depends on the interplay between the thermal broadening and the quantum confinement. It is pointed out here that the modulation geometry and material parameters can provide design tools for Seebeck coefficient enhancement in nanowires.

Zianni, Xanthippi

2014-04-01

170

Effects of SiC Nanodispersion on the Thermoelectric Properties of p-Type and n-Type Bi2Te3-Based Alloys  

NASA Astrophysics Data System (ADS)

Polycrystalline p-type Bi0.5Sb1.5Te3 and n-type Bi2Te2.7Se0.3 thermoelectric (TE) alloys containing a small amount (vol.% ?5) of SiC nanoparticles were fabricated by mechanical alloying and spark plasma sintering. It was revealed that the effects of SiC addition on TE properties can be different between p-type and n-type Bi2Te3-based alloys. SiC addition slightly increased the power factor of the p-type materials by decreasing both the electrical resistivity ( ?) and Seebeck coefficient ( ?), but decreased the power factor of n-type materials by increasing both ? and ?. Regardless of the conductivity type, the thermal conductivity was reduced by dispersing SiC nanoparticles in the Bi2Te3-based alloy matrix. As a result, a small amount (0.1 vol.%) of SiC addition increased the maximum dimensionless figure of merit ( ZT max) of the p-type Bi0.5Sb1.5Te3 alloys from 0.88 for the SiC-free sample to 0.97 at 323 K, though no improvement in TE performance was obtained in the case of n-type Bi2Te2.7Se0.3 alloys. Importantly, the SiC-dispersed alloys showed better mechanical properties, which can improve material machinability and device reliability.

Liu, Da-Wei; Li, Jing-Feng; Chen, Chen; Zhang, Bo-Ping

2011-05-01

171

Spray pyrolysis of tin selenide thin-film semiconductors: the effect of selenium concentration on the properties of the thin films  

NASA Astrophysics Data System (ADS)

Thin films of tin selenide (SnxSey) with an atomic ratio of , 1 and 1.5 were prepared on a glass substrate at T = 470°C using a spray pyrolysis technique. The initial materials for the preparation of the thin films were an alcoholic solution consisting of tin chloride (SnCl4· 5H2O) and selenide acide (H2SeO3). The prepared thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy, scanning tunneling microscopy, scanning helium ion microscopy, and UV-vis spectroscopy. The photoconductivity and thermoelectric effects of the SnxSey thin films were then studied. The SnxSey thin films had a polycrystalline structure with an almost uniform surface and cluster type growth. The increasing atomic ratio of r in the films, the optical gap, photosensitivity and Seebeck coefficient were changed from 1.6 to 1.37 eV, 0.01 to 0.31 and -26.2 to -42.7 mV/K (at T = 350 K), respectively. In addition, the XRD patterns indicated intensity peaks in r = 1 that corresponded to the increase in the SnSe and SnSe2 phases.

Fadavieslam, M. R.; Bagheri-Mohagheghi, M. M.

2013-08-01

172

Optical and electrical properties and phonon drag effect in low temperature TEP measurements of AgSbSe2 thin films  

NASA Astrophysics Data System (ADS)

Polycrystalline thin films of silver antimony selenide have been deposited using a reactive evaporation technique onto an ultrasonically cleaned glass substrate at a vacuum of 10?5 torr. The preparative parameters, like substrate temperature and incident fluxes, have been properly controlled in order to get stoichiometric, good quality and reproducible thin film samples. The samples are characterized by XRD, SEM, AFM and a UV—vis—NIR spectrophotometer. The prepared sample is found to be polycrystalline in nature. From the XRD pattern, the average particle size and lattice constant are calculated. The dislocation density, strain and number of crystallites per unit area are evaluated using the average particle size. The dependence of the electrical conductivity on the temperature has also been studied and the prepared AgSbSe2 samples are semiconducting in nature. The AgSbSe2 thin films exhibited an indirect allowed optical transition with a band gap of 0.64 eV. The compound exhibits promising thermoelectric properties, a large Seebeck coefficient of 30 mV/K at 48 K due to strong phonon electron interaction. It shows a strong temperature dependence on thermoelectric properties, including the inversion of a dominant carrier type from p to n over a low temperature range 9–300 K, which is explained on the basis of a phonon drag effect.

Namitha Asokan, T.; Urmila, K. S.; Jacob, Rajani; Reena Philip, Rachel; Okram, G. S.; Ganesan, V.; Pradeep, B.

2014-05-01

173

Post-annealing Effect on Microstructures and Thermoelectric Properties of Bi0.45Sb1.55Te3 Thin Films Deposited by Co-sputtering  

NASA Astrophysics Data System (ADS)

p-Type Bi0.45Sb1.55Te3 thermoelectric (TE) thin films have been prepared at room temperature by a magnetron cosputtering process. The effect of postannealing on the microstructure and TE properties of Bi0.45Sb1.55Te3 films has been investigated in the temperature range from room temperature to 350°C. x-Ray diffraction analysis shows that the annealed films have polycrystalline rhombohedral crystal structure, and the average grain size increases from 36 nm to 64 nm with increasing annealing temperature from room temperature to 350°C. Electron probe microanalysis shows that annealing above 250°C can cause Te reevaporation, which induces porous thin films and dramatically affects electrical transport properties of the thin films. TE properties of the films have been investigated at room temperature. The hole concentration shows a trend from descent to ascent and has a minimum value at the annealing temperature of 200°C, while the Seebeck coefficient shows an opposite trend and a maximum value of 245 ?V K-1. The electrical resistivity monotonically decreases from 19.8 m? cm to 1.4 m? cm with increasing annealing temperature. Correspondingly, a maximum value of power factor, 27.4 ?W K-2 cm-1, was obtained at the annealing temperature of 250°C.

Song, Junqiang; Chen, Xihong; Tang, Yunshan; Yao, Qin; Chen, Lidong

2012-11-01

174

Effect of ceramic dispersion on thermoelectric properties of nano-ZrO{sub 2}/CoSb{sub 3} composites  

SciTech Connect

In the present work, nano-ZrO{sub 2}/CoSb{sub 3} composites were fabricated by milling ZrO{sub 2} and CoSb{sub 3} powders and hot pressing at different sintering temperatures. For the prepared compacts, the phase purity, microstructure, and temperature-dependent thermoelectric properties were characterized. The effect of nano-ZrO{sub 2} dispersion on composite electrical conductivity and thermal conductivity is strictly clarified by comparing the transport properties of the nondispersed and dispersed CoSb{sub 3} at identical porosity, so that the effect of porosity on thermoelectric parameters could be eliminated. The effect of the insulating inclusion itself on transport properties is also considered and eliminated using effective media theories. It is clearly verified that charge carrier scattering and phonon scattering occur simultaneously to lower the electrical conductivity and the thermal conductivity of CoSb{sub 3} due to the introduction of nano-ZrO{sub 2} inclusions. The investigated composites show higher electrical conductivity due to existence of metallic Sb and lower thermal conductivity because of nanodispersion. At the ranges of high measuring temperature (673-723 K) and low porosity (6%-9%), the ratio of electrical conductivity to thermal conductivity of the dispersed CoSb{sub 3} is higher than that of nondispersed CoSb{sub 3}, and the dimensionless figure of merit (ZT) of the composite could probably be improved at these ranges with the enhanced ratio of electrical conductivity to thermal conductivity and Seebeck coefficient, which is assumed to be increased by a potential barrier scattering.

He, Zeming; Stiewe, Christian; Platzek, Dieter; Karpinski, Gabriele; Mueller, Eckhard; Li, Shanghua; Toprak, Muhammet; Muhammed, Mamoun [Institute of Materials Research, German Aerospace Center (DLR), D-51170 Cologne (Germany); Materials Chemistry Division, Royal Institute of Technology (KTH), SE-10044 Stockholm (Sweden)

2007-02-15

175

The Effect of Grain Size and Volume Fraction on Charge Transport in Thermoelectric Nanocomposite of Bi2Te3Sb2Te3  

Microsoft Academic Search

It was shown by D. J. Bergman and L. J. Fel (J. Appl. Phys. 85, 8205, 1999) that in a composite material thermoelectric power factor, the product of the square of the Seebeck coefficient and electrical conductivity, can be enhanced over that of the individual constituents, but the figure-of- merit cannot. It is expected that this predication fails in nanocomposites

Payam Norouzzadeh; Daryoosh Vashaee

2012-01-01

176

Are Effective Properties Effective?  

SciTech Connect

The effective moduli (effective Young's modulus, effective Poisson's ratio, effective shear modulus, and effective bulk modulus) of dispersed-phase-reinforced composite materials are determined at the mesoscopic level using three-dimensional parallel boundary element simulations. By comparing the mesoscopic BEM results and the macroscopic results based on effective properties, limitations in the effective property approach have been examined.

Han, Ru; Ingber, Marc S. [Department of Mechanical Engineering, University of New Mexico, NM 87131 (United States); Hsiao, S.-C. [Department of Hydraulic and Ocean Engineering, National Cheng-Kung University No. 1, Ta-Hsueh Road Tainan 701, Taiwan (China)

2008-02-15

177

Temperature Gradient Measurements by Using Thermoelectric Effect in CNTs-Silicone Adhesive Composite  

PubMed Central

This work presents the fabrication and investigation of thermoelectric cells based on composite of carbon nanotubes (CNT) and silicone adhesive. The composite contains CNT and silicon adhesive 1?1 by weight. The current-voltage characteristics and dependences of voltage, current and Seebeck coefficient on the temperature gradient of cell were studied. It was observed that with increase in temperature gradient the open circuit voltage, short circuit current and the Seebeck coefficient of the cells increase. Approximately 7 times increase in temperature gradient increases the open circuit voltage and short circuit current up to 40 and 5 times, respectively. The simulation of experimental results is also carried out; the simulated results are well matched with experimental results.

Chani, Muhammad Tariq Saeed; Karimov, Kh. S.; Asiri, Abdullah M.; Ahmed, Nisar; Bashir, Muhammad Mehran; Khan, Sher Bahadar; Rub, Malik Abdul; Azum, Naved

2014-01-01

178

Temperature Gradient Measurements by Using Thermoelectric Effect in CNTs-Silicone Adhesive Composite.  

PubMed

This work presents the fabrication and investigation of thermoelectric cells based on composite of carbon nanotubes (CNT) and silicone adhesive. The composite contains CNT and silicon adhesive 1?1 by weight. The current-voltage characteristics and dependences of voltage, current and Seebeck coefficient on the temperature gradient of cell were studied. It was observed that with increase in temperature gradient the open circuit voltage, short circuit current and the Seebeck coefficient of the cells increase. Approximately 7 times increase in temperature gradient increases the open circuit voltage and short circuit current up to 40 and 5 times, respectively. The simulation of experimental results is also carried out; the simulated results are well matched with experimental results. PMID:24748375

Chani, Muhammad Tariq Saeed; Karimov, Kh S; Asiri, Abdullah M; Ahmed, Nisar; Bashir, Muhammad Mehran; Khan, Sher Bahadar; Rub, Malik Abdul; Azum, Naved

2014-01-01

179

Effect of ruthenium substitution in layered sodium cobaltate Na{sub x}CoO{sub 2}: Synthesis, structural and physical properties  

SciTech Connect

Solid-state synthesis of Na{sub 0.71}Co{sub 1-x}Ru{sub x}O{sub 2} compositions shows that ruthenium can be substituted for cobalt in the hexagonal Na{sub 0.71}CoO{sub 2} phase up to x=0.5. The cell expands continuously with increasing ruthenium content. All mixed Co-Ru phases show a Curie-Weiss behaviour with no evidence of magnetic ordering down to 2 K. Unlike the parent phase Na{sub 0.71}CoO{sub 2}, ruthenium-substituted phases are all semiconducting. They exhibit high thermoelectric power, with a maximum of 165 muV/K at 300 K for x=0.3. The Curie constant C and Seebeck coefficient S show a non-monotonic evolution as a function of ruthenium content, demonstrating a remarkable interplay between magnetic properties and thermoelectricity. The presence of ruthenium has a detrimental effect on water intercalation and superconductivity in this system. Applying to Ru-substituted phases the oxidative intercalation of water known to lead to superconductivity in the Na{sub x}CoO{sub 2} system yields a 2-water layer hydrate only for x=0.1, and this phase is not superconducting down to 2 K. - Graphical Abstract: Effect of ruthenium substitution on thermoelectric power in Na{sub 0.71}Co{sub 1-x}Ru{sub x}O{sub 2} (left) and on low-temperature ac susceptibility in hydrated derivative (right).

Strobel, Pierre, E-mail: pierre.strobel@grenoble.cnrs.f [Institut Neel, CNRS, and Universite Joseph Fourier, B.P. 166, 38042 Grenoble, Cedex 9 (France); Muguerra, Herve [Institut Neel, CNRS, and Universite Joseph Fourier, B.P. 166, 38042 Grenoble, Cedex 9 (France); Hebert, Sylvie [CRISMAT (UMR CNRS 6508), ENSI-Caen, F-14050 Caen Cedex (France); Pachoud, Elise [Institut Neel, CNRS, and Universite Joseph Fourier, B.P. 166, 38042 Grenoble, Cedex 9 (France); CRISMAT (UMR CNRS 6508), ENSI-Caen, F-14050 Caen Cedex (France); Colin, Claire [Institut Neel, CNRS, and Universite Joseph Fourier, B.P. 166, 38042 Grenoble, Cedex 9 (France); Julien, Marc-Henri [Laboratoire de Spectrometrie Physique, UMR CNRS 5588 and Universite Joseph Fourier, 38402 Saint Martin d'Heres (France)

2009-07-15

180

Effect of partial La filling on the local electronic properties of LaxCo4Sb12 studied using 59Co NMR  

NASA Astrophysics Data System (ADS)

We present a systematic investigation of the LaxCo4Sb12 skutterudites with x<=0.2 using 59Co nuclear magnetic resonance (NMR) spectroscopy. The NMR line shape, the quadrupole splitting, the Knight shift and the spin lattice relation rate of each compound have been identified. For LaxCo4Sb12, the central transition and the quadrupole linewidths increase with the La concentration because of the effect of the inhomogeneous electric field gradient. In addition, each linewidth exhibits a temperature-independent behavior, confirming the non-magnetic characteristic of these materials. The results of the isotropic Knight shift and the spin-lattice relaxation rate provide further information on the electronic structure around the Fermi surfaces of these compounds. In La0.1Co4Sb12 and La0.2Co4Sb12, the low-temperature NMR relaxation rates follow the Korringa behavior, indicating a finite density of carriers at the Fermi level. The high-temperature relaxation rates go over to a semiconductor-like activated form, being consistent with a semimetallic response. A detailed analysis of the spin-lattice relaxation rate established that the partial Co 3d Fermi-level density of states (DOS) increases with the La content. The NMR observations were interpreted in terms of a two-band scenario that consists of predominant d-electron features at low temperatures and exotic behavior of s-character electrons at high temperatures. Moreover, the obtained Fermi-level DOS show good agreement with those observed from the electrical conductivity and the Seebeck coefficient measurements in these La-filled skutterudites.

Lue, C. S.; Huang, S. M.; Kuo, C. N.; Huang, F.-T.; Chu, M.-W.

2008-08-01

181

Effect of Annealing Temperature on the Thermoelectric Properties of the Bi0.5Sb1.5Te3 Thin Films Prepared by Radio-Frequency Sputtering  

NASA Astrophysics Data System (ADS)

The effect of annealing temperature on the crystallinity, thermoelectric properties, and surface morphology of the Bi0.5Sb1.5Te3 thin films prepared on SiO2/Si substrate by radio-frequency (RF) magnetron sputtering was investigated using X-ray diffraction (XRD), the four-point probe method, and scanning electron microscopy (SEM). XRD results show that the crystallite structure of the Bi x Sb2- x Te3 thin films belong to Bi0.5Sb1.5Te3. When the Bi x Sb2- x Te3 thin films were annealed between 423 K and 523 K (150 °C and 250 °C) for 10 minutes, the crystallinity of the thin films continuously increases with the temperature increase. In addition, the (015) reflection plane as the preferred orientation and the oxidation compound of Bi3.73Sb1.5O3 first appeared when the Bi0.5Sb1.5Te3 thin films were annealed at 523 K (250 °C) for 10 minutes. An activation energy of 51.66 kJ/mol for crystallite growth of Bi0.5Sb1.5Te3 thin films annealed between 423 K and 523 K (150 °C and 250 °C) for 10 minutes was obtained. The resistivity was 2.69 × 102 and 5.93 × 10 ??·m, respectively, for the as-deposited Bi0.5Sb1.5Te3 thin films and annealed at 523 K (250 °C) for 10 minutes. The maximum values of the Seebeck coefficient and power factor were 256.5 ?V/K and 1.12 × 103 ?W/m·K2, respectively, for the Bi0.5Sb1.5Te3 thin films annealing treatment at 523 K (250 °C) for 10 minutes.

Lin, Huey-Jiuan; Kang, Kai-Jyun; Hwang, Jenn-Dong; Chu, Hsu-Shen; Huang, Hong-Hsin; Wang, Moo-Chin

2013-05-01

182

Model for Increasing the Power Obtained from a Thermoelectric Generator Module  

NASA Astrophysics Data System (ADS)

We have developed a model for finding the most efficient way of increasing the power obtained from a thermoelectric generator (TEG) module with a variety of operating conditions and limitations. The model is based on both thermoelectric principles and thermal resistance circuits, because a TEG converts heat into electricity consistent with these two theories. It is essential to take into account thermal contact resistance when estimating power generation. Thermal contact resistance causes overestimation of the measured temperature difference between the hot and cold sides of a TEG in calculation of the theoretical power generated, i.e. the theoretical power is larger than the experimental power. The ratio of the experimental open-loop voltage to the measured temperature difference, the effective Seebeck coefficient, can be used to estimate the thermal contact resistance in the model. The ratio of the effective Seebeck coefficient to the theoretical Seebeck coefficient, the Seebeck coefficient ratio, represents the contact conditions. From this ratio, a relationship between performance and different variables can be developed. The measured power generated by a TEG module (TMH400302055; Wise Life Technology, Taiwan) is consistent with the result obtained by use of the model; the relative deviation is 10%. Use of this model to evaluate the most efficient means of increasing the generated power reveals that the TEG module generates 0.14 W when the temperature difference is 25°C and the Seebeck coefficient ratio is 0.4. Several methods can be used triple the amount of power generated. For example, increasing the temperature difference to 43°C generates 0.41 W power; improving the Seebeck coefficient ratio to 0.65 increases the power to 0.39 W; simultaneously increasing the temperature difference to 34°C and improving the Seebeck coefficient ratio to 0.5 increases the power to 0.41 W. Choice of the appropriate method depends on the limitations of system, the cost, and the environment.

Huang, Gia-Yeh; Hsu, Cheng-Ting; Yao, Da-Jeng

2014-06-01

183

Effect of Heat Treatment on the Thermoelectric Properties of Bismuth-Antimony-Telluride Prepared by Mechanical Deformation and Mechanical Alloying  

NASA Astrophysics Data System (ADS)

In this work, p-type 20%Bi2Te3-80%Sb2Te3 bulk thermoelectric (TE) materials were prepared by mechanical deformation (MD) of pre-melted ingot and by mechanical alloying (MA) of elemental Bi, Sb, and Te granules followed by cold-pressing. The dependence on annealing time of changes of microstructure and TE properties of the prepared samples, including Seebeck coefficient, electrical resistivity, thermal conductivity, and figure-of-merit, was investigated. For both samples, saturation of the Seebeck coefficient and electrical resistivity were observed after annealing for 1 h at 380°C. It is suggested that energy stored in samples prepared by both MA and MD facilitated their recrystallization within short annealing times. The 20%Bi2Te3-80%Sb2Te3 sample prepared by MA followed by heat treatment had higher a Seebeck coefficient and electrical resistivity than specimens fabricated by MD. Maximum figures-of-merit of 3.00 × 10-3/K and 2.85 × 10-3/K were achieved for samples prepared by MA and MD, respectively.

Lee, Deuk-Hee; Lee, Jae-Uk; Jung, Sung-Jin; Baek, Seung-Hyub; Kim, Ju-Heon; Kim, Dong-Ik; Hyun, Dow-Bin; Kim, Jin-Sang

2014-06-01

184

Effect of Heat Treatment on the Thermoelectric Properties of Bismuth-Antimony-Telluride Prepared by Mechanical Deformation and Mechanical Alloying  

NASA Astrophysics Data System (ADS)

In this work, p-type 20%Bi2Te3-80%Sb2Te3 bulk thermoelectric (TE) materials were prepared by mechanical deformation (MD) of pre-melted ingot and by mechanical alloying (MA) of elemental Bi, Sb, and Te granules followed by cold-pressing. The dependence on annealing time of changes of microstructure and TE properties of the prepared samples, including Seebeck coefficient, electrical resistivity, thermal conductivity, and figure-of-merit, was investigated. For both samples, saturation of the Seebeck coefficient and electrical resistivity were observed after annealing for 1 h at 380°C. It is suggested that energy stored in samples prepared by both MA and MD facilitated their recrystallization within short annealing times. The 20%Bi2Te3-80%Sb2Te3 sample prepared by MA followed by heat treatment had higher a Seebeck coefficient and electrical resistivity than specimens fabricated by MD. Maximum figures-of-merit of 3.00 × 10-3/K and 2.85 × 10-3/K were achieved for samples prepared by MA and MD, respectively.

Lee, Deuk-Hee; Lee, Jae-Uk; Jung, Sung-Jin; Baek, Seung-Hyub; Kim, Ju-Heon; Kim, Dong-Ik; Hyun, Dow-Bin; Kim, Jin-Sang

2014-04-01

185

Experimental Test of the Spin Mixing Interface Conductivity Concept  

NASA Astrophysics Data System (ADS)

We perform a quantitative, comparative study of the spin pumping, spin Seebeck, and spin Hall magnetoresistance effects, all detected via the inverse spin Hall effect in a series of over 20yttriumirongarnet/Pt samples. Our experimental results fully support present, exclusively spin current-based, theoretical models using a single set of plausible parameters for spin mixing conductance, spin Hall angle, and spin diffusion length. Our findings establish the purely spintronic nature of the aforementioned effects and provide a quantitative description, in particular, of the spin Seebeck effect.

Weiler, Mathias; Althammer, Matthias; Schreier, Michael; Lotze, Johannes; Pernpeintner, Matthias; Meyer, Sibylle; Huebl, Hans; Gross, Rudolf; Kamra, Akashdeep; Xiao, Jiang; Chen, Yan-Ting; Jiao, HuJun; Bauer, Gerrit E. W.; Goennenwein, Sebastian T. B.

2013-10-01

186

Impurity Band Effects in Thermoelectric Materials  

NASA Astrophysics Data System (ADS)

The possibility of improvement of the power factor through introduction of impurity bands is considered. The contributions to the Seebeck coefficient and electrical conductivity from carriers in an impurity band are expressed in terms of the Fermi energy and the position of the impurity levels relative to the edge of the main band. Surprisingly, it is found that the presence of an impurity band generally brings little benefit, and in fact, when it lies near the edge of the main band, the power factor may be significantly reduced. Our findings are consistent with the observation that the figure of merit of PbTe is improved by the presence of deep-lying thallium states. They also indicate that, for Bi2Te3, compensation for nonstoichiometry by counterdoping may not yield the highest power factor.

Goldsmid, H. J.

2012-08-01

187

Thermoelectric properties of electrolessly etched silicon nanowire arrays  

NASA Astrophysics Data System (ADS)

Patterning silicon as nanowires with roughened sidewalls enhances the thermoelectric figure-of-merit ZT by order of magnitude compared to the bulk at 300 K [1]. The enhancement is mainly achieved by the remarkable reduction in the thermal conductivity below 5 W/mK at 300 K with only a negligible effect on the power factor of these nanowires. While the focus remained on understanding the implications of surface disorder on the thermal conductivity, the phonon transport effects on the Seebeck coefficient of these wires remains largely unexplored. We developed an electroless etching technique to generate nanowire arrays (NWAs) with controlled surface roughness, morphology, porosity and doping [2]. We conduct the simultaneous device-level measurements of the Seebeck coefficient and thermal conductivity of the NWAs using frequency domain techniques. We observe that nano-structuring quenches the phonon drag [3] in NWAs thereby reducing the Seebeck coefficient by ˜25% compared to the bulk at degenerate doping levels. Further, we observe that the sidewall roughness greater than 3 nm roughness height lowers the thermal conductivity 75% below the Casimir limit [4] with 10% - 15% increase in Seebeck coefficient. The porous NWAs show thermal conductivity close to the amorphous limit of Si with enhancement in the Seebeck coefficient primarily due to the carrier depletion. References: [1] A. I. Hochbaum et al, Nature 451, 163-167 (2008). [2] K. Balasundaram et. al., Nanotechnology 23, 305304 (2012). [3] C. Herring, Phys. Rev. 96, 1163 (1954). [4] H. G. B. Casimir, Physica 5, 495 (1938).

Sadhu, Jyothi; Tian, Hongxiang; Ma, Jun; Valavala, Krishna; Singh, Piyush; Sinha, Sanjiv

2013-03-01

188

Synthesis and thermoelectric properties of RuO{sub 2} nanorods  

SciTech Connect

We have explored the effect of the O/Ru ratio on the morphology and the Seebeck coefficient of RuO{sub 2} nanorods (space group P4{sub 2}/mnm) synthesized by reactive sputtering. At an O/Ru ratio of 1.69, a faceted surface is observed, while nanorod formation occurs at O/Ru ratios of 2.03 and 2.24. Using classical molecular dynamics with the potential parameters derived in this work, we show that volatile species enable nanorod formation. Based on ab initio calculations, two effects of the nanorod formation on the Seebeck coefficient are observed: (i) increase due to additional states in the vicinity of the Fermi level and (ii) decrease due to oxygen point defects (volatile species). These two competing effects give rise to a moderate increase in the Seebeck coefficient upon nanorod formation.

Music, Denis; Basse, Felix H.-U.; Schneider, Jochen M. [Materials Chemistry, RWTH Aachen University, D-52056 Aachen (Germany); Hassdorf, Ralf [Institute of Materials Research, German Aerospace Centre (DLR), D-51147 Cologne (Germany)

2010-07-15

189

Ballistic thermoelectric transport in structured nanowires  

NASA Astrophysics Data System (ADS)

Thermoelectric (TE) devices are solid-state energy converters that can be used for power generation through the Seebeck effect and TE cooling through the Peltier effect. Nanostructures give great opportunities to engineer TE energy conversion efficiency. In this work, we investigate TE transport properties in structured nanowires (NWs) in the ballistic transport regime, where the NWs are bent, kinked, stubbed and segmented like a superlattice nanowire using the Green’s function method and the Landauer–Büttiker formula. A large Seebeck coefficient is found when the transmission gap appears due to the quantum interference effect of electrons. The sign of the Seebeck coefficient can be controlled by the geometries of these structured NWs. This finding is helpful for the design of nanoscale TE devices, such as thermocouple, with the same type of material doping rather than those comprised of n-type and p-type materials.

Wang, Biao; Zhou, Jun; Yang, Ronggui; Li, Baowen

2014-06-01

190

Improved thermoelectric cooling based on the Thomson effect  

NASA Astrophysics Data System (ADS)

Traditional thermoelectric Peltier coolers exhibit a cooling limit which is primarily determined by the figure of merit, zT. Rather than a fundamental thermodynamic limit, this bound can be traced to the difficulty of maintaining thermoelectric compatibility. Self-compatibility locally maximizes the cooler's coefficient of performance for a given zT and can be achieved by adjusting the relative ratio of the thermoelectric transport properties that make up zT. In this study, we investigate the theoretical performance of thermoelectric coolers that maintain self-compatibility across the device. We find that such a device behaves very differently from a Peltier cooler, and we term self-compatible coolers “Thomson coolers” when the Fourier heat divergence is dominated by the Thomson, as opposed to the Joule, term. A Thomson cooler requires an exponentially rising Seebeck coefficient with increasing temperature, while traditional Peltier coolers, such as those used commercially, have comparatively minimal change in Seebeck coefficient with temperature. When reasonable material property bounds are placed on the thermoelectric leg, the Thomson cooler is predicted to achieve approximately twice the maximum temperature drop of a traditional Peltier cooler with equivalent figure of merit (zT). We anticipate that the development of Thomson coolers will ultimately lead to solid-state cooling to cryogenic temperatures.

Snyder, G. Jeffrey; Toberer, Eric S.; Khanna, Raghav; Seifert, Wolfgang

2012-07-01

191

Seebeck Coefficient and Electrical Resistivity of Some Rare Earth Ternary Sulfides La/sub 3-x/M/sub x/S sub 4 (M = Sm, Eu, Yb).  

National Technical Information Service (NTIS)

Binary lanthanum sulfides with compositions between La sub 2 S sub 3 and La sub 3 S sub 4 form a continuous series of solid solutions in the high temperature gamma form and have been reported to have high figures of merit. In this study, in order to achie...

B. J. Beaudry J. F. Nakahara K. A. Gschneidner M. J. Tschetter T. Takeshita

1986-01-01

192

Self-Consistent Drift-Diffusion Transport in Thermoelectrics and Implications for Measuring the Scattering Parameter  

NASA Astrophysics Data System (ADS)

We present a microscopic model of the Seebeck effect based on a generalized drift-diffusion equation and use it to predict a simple relationship between the electric field within an operating thermoelectric and the scattering parameter. Our model replicates existing theoretical results and permits an intuitive spatial picture of the Seebeck effect. A similar formalism was independently developed by Cai and Mahan, but this work includes numerical results for high dopant concentrations where the thermoelectric power factor is maximized. Based on these results, we propose that measurement of the bulk electric field should constitute a measurement of the scattering parameter, the improvement of which could lead to greater thermoelectric efficiency.

Santhanam, Parthiban; Ram, Rajeev J.

2010-09-01

193

Effect of Nickel Substitution on Defect Chemistry, Electrical Properties, and Dimensional Stability of Calcium-Doped Yttrium Chromite  

SciTech Connect

The effect of nickel substitution on defect chemistry, electrical properties, and dimensional stability of calcium-doped yttrium chromite was studied for use as an interconnect material in high temperature solid oxide fuel cells (SOFCs). The compositions of Y0.8Ca0.2Cr1-xNixO3±? (x=0-0.15), prepared using the glycine nitrate process, showed single phase orthorhombic perovskite structures over a wide range of oxygen partial pressures (10^-17 atm ? pO2 ? 0.21 atm). X-ray diffraction (XRD) analysis indicated that most of the nickel ions replacing chromium ions are divalent and act as acceptor dopants, leading to a substantial increase in conductivity. In particular, the conductivity at 900 degree C in air increased from 10 S/cm to 34 S/cm with 15% nickel substitution, and an increase in charge carrier density was confirmed by Seebeck measurements. A point defect model was derived, and the relationship between electrical conductivity and oxygen partial pressure was successfully fitted into the proposed model. The defect modeling results indicated that nickel substitution improves the stability of calcium-doped yttrium chromite toward reduction and suppresses the oxygen vacancy formation, which results in significantly increased electrical conductivity in reducing environment. The electrical conductivity of Y0.8Ca0.2Cr0.85Ni0.15O3±? at 900 degree C in reducing atmosphere (pO2=10^-17 atm) was 5.8 S/cm, which was more than an order of magnitude higher than that of Y0.8Ca0.2CrO3±? (0.2 S/cm). Improved stability in reducing atmosphere was further confirmed by dilatometry measurements showing reduced isothermal "chemical" expansion, and the isothermal expansion in reducing atmosphere (pO2=10^-17 atm) at 900 degree C decreased from 0.07% for Y0.8Ca0.2CrO3±? to 0.03% for Y0.8Ca0.2Cr0.85Ni0.15O3±?. Based on these results, enhanced electrical performance and mechanical integrity is expected with nickel substitution on calcium-doped yttrium chromite in SOFC operating conditions.

Yoon, Kyung J.; Stevenson, Jeffry W.; Marina, Olga A.

2011-06-30

194

A thermoelectric scanning facility for the study of elemental thermocouples  

NASA Astrophysics Data System (ADS)

A scanning facility for studying the thermoelectric behaviour of the metals used in elemental thermocouples (Au, Pt and Pd) is described. The facility effectively measured changes in Seebeck coefficient along a 560 mm length of each of three wires, relative to a fourth, by moving them through a 50 mm long, EMF-producing zone into a uniform-temperature region at 250 °C. The uniform region was stable to within 0.7 mK and EMF measurements were made to 10 nV (equivalent to about 1 mK). Accordingly, the facility is able to detect changes of ~10 ppm in Seebeck coefficient. The precautions necessary to work at this accuracy are detailed and preliminary data on the changes that occur at temperatures up to 1000 °C are reported. For example, the measured Seebeck coefficient of Pd decreased at temperatures in the range 550 to 850 °C, a change opposite in sign to that previously reported.

Bentley, Robin E.

2000-05-01

195

Doppler Effect  

NSDL National Science Digital Library

This site offers information on the classical doppler effect, the relativistic doppler effect, aberration, and the transverse doppler effect. It also discusses wave fronts, first-order and second order effect, light-time correction, Galilean transformation, and parallax.

Calvert, J. B.

2010-08-19

196

Implications of nanostructuring on the thermoelectric properties in half-Heusler alloys  

NASA Astrophysics Data System (ADS)

High energy ball milled Zr0.25Hf0.75NiSn alloys subjected to spark plasma sintering show an enhanced thermoelectric figure of merit in comparison with its normal bulk material synthesized by arc-melting process. The enhancement is due to increase in Seebeck coefficient with simultaneous decrease in thermal conductivity which follows due to increase in the cell volume. Theoretical calculations find that volume expansion facilitates band narrowing effects leading to high Seebeck coefficient and that decreasing orbital overlap which results in weak bonding leads to dampening the phonon propagation in addition to the interface scattering of phonons from phase boundaries.

Bhardwaj, A.; Misra, D. K.; Pulikkotil, J. J.; Auluck, S.; Dhar, A.; Budhani, R. C.

2012-09-01

197

Modern Thermocouple Experiment.  

ERIC Educational Resources Information Center

Describes a thermocouple circuit used to measure Joule heating as well as Peltier heating and cooling for a copper-Constantan metallic junction. Shows how the Seebeck effect from a thermocouple can monitor the temperature condition of a junction with regard to input power and Peltier effect. (Author/GA)

Chang, K. N.; And Others

1978-01-01

198

Thermoelectric Devices: Solid-State Refrigerators and Electrical Generators in the Classroom  

Microsoft Academic Search

Thermoelectric devices are solid-state devices that convert thermal energy from a temperature gradient into electrical energy (the Seebeck effect) or convert electrical energy into a temperature gradient (the Peltier effect). The first application is used most notably in spacecraft power generation systems (for example, in Voyager I and II) and in thermocouples for temperature measurement, while the second application is

Edmund J. Winder; Arthur B. Ellis; George C. Lisensky

1996-01-01

199

The effect of phonon-grain boundary scattering on the lattice thermal conductivity and thermoelectric conversion efficiency of heavily doped fine-grained, hot-pressed silicon germanium alloy  

Microsoft Academic Search

The preparation of fine-grained high-density compacts of heavily doped n-type Si63.5Ge36.5 alloy and the measurement of their thermal diffusivity over the temperature range 300 to 1150 K are reported. The compacts investigated possessed grain sizes (L) in the range 10Seebeck coefficient and electrical resistivity do not change with

D. M. Rowe; V. S. Shukla

1981-01-01

200

Thermoelectric power generation for battery charging  

Microsoft Academic Search

Thermoelectric generators use the Seebeck effect to produce electrical power from a temperature difference caused by heat energy flow. In this paper the principle of using thermoelectrically converted heat energy for powering portable electronic equipment or charging its battery has been investigated for a lap-top computer. The thermoelectric battery charger developed, consists of a thermoelectric converter system, powered from butane

Mahmudur Rahman; Roger Shuttleworth

1995-01-01

201

Electrical Properties and Surface Microtopographic Studies of Tungsten Disulfide Single Crystals Grown by CVT Technique  

Microsoft Academic Search

The single crystals of tungsten disulphide (WS2) were grown by chemical vapor transport (CVT) technique, using iodine as the transporting agent. The stoichiometric composition and the crystallographic lattice parameters of the grown crystals were determined by EDAX and X?ray diffraction (XRD) techniques, respectively. The Hall effect measurement and the Seebeck coefficient variation with temperature confirmed that the single crystals were

Sunil Chaki; Ajay Agarwal

2008-01-01

202

REVIEW ARTICLE: Review of micromachined thermopiles for infrared detection  

Microsoft Academic Search

During the last few years, thermopiles have come increasingly under the spotlight of commercial infrared sensing. This growing interest has motivated us to write an overview of micromachined thermopiles. The first part deals with the Seebeck effect and discusses the most important physical parameters with their interactions. We also describe the main noise sources and give a derivation of the

A. Graf; M. Arndt; M. Sauer; G. Gerlach

2007-01-01

203

Appearance of thermochemical emf in some conducting materials  

Microsoft Academic Search

The appearance of an emf in conductors when they are heated is described by the Seebeck and Thompson effects. If some part of the surface of a conductor is covered by a pyrotechnical material and ignited, then while the pyrotechnical material is burning and after it has burned, an emf arises at the ends of the conductor. The direction of

Y. S. Petrov; V. V. Maslikhov; V. D. Shcheglov

1983-01-01

204

Thermoelectric metal comparator determines composition of alloys and metals  

NASA Technical Reports Server (NTRS)

Emf comparing device nondestructively inspects metals and alloys for conformance to a chemical specification. It uses the Seebeck effect to measure the difference in emf produced by the junction of a hot probe and the junction of a cold contact on the surface of an unknown metal.

Stone, C. C.; Walker, D. E.

1967-01-01

205

Effects of Bi doping on the thermoelectric properties of ?-Zn4Sb3  

NASA Astrophysics Data System (ADS)

The thermoelectric properties of Bi-doped compounds (Zn1-xBix)4Sb3 (x=0,0.0025,0.005,0.01) were studied experimentally as well as theoretically. The results indicate that low-temperature (T<300 K) thermal conductivity of moderately doped (Zn0.9975Bi0.0025)4Sb3 reduces remarkably as compared with that of Zn4Sb3 due to enhanced phonon scattering of impurity (dopant). Electrical resistivity and Seebeck coefficient increase monotonically with increase in the Bi content resulting mainly from decrease in carrier concentration. Moreover, first-principle calculations were performed on the occupation options of Bi atoms in ?-Zn4Sb3, which show that Bi will preferentially occupy the Zn sites and not Sb sites and act as donors, being consistent with the experimental observations. In addition, the lightly doped compound (Zn0.9975Bi0.0025)4Sb3 exhibits the best thermoelectric performance due to the improvement in both its thermal conductivity and Seebeck coefficient, whose figure of merit, ZT, is about 1.5 times larger than that of ?-Zn4Sb3 at 300 K.

Qin, X. Y.; Liu, M.; Pan, L.; Xin, H. X.; Sun, J. H.; Wang, Q. Q.

2011-02-01

206

Study of Interesting Solidification Phenomena on the Ground and in Space (MEPHISTO)  

NASA Technical Reports Server (NTRS)

Real-time Seebeck voltage variations in a Sn-Bi melt during directional solidification in the MEPHISTO spaceflight experiment flown on the USMP-3 mission, can be correlated with well characterized thruster firings and an Orbiter Main System (OMS) burn. The Seebeck voltage measurement is related to the response of the instantaneous average melt composition at the melt-crystal interface. This allowed us to make a direct comparison of numerical simulations with the experimentally obtained Seebeck signals. Based on the results of preflight and real-time computations, several well-defined thruster firing events were programmed to occur at specific times during the experiment. In particular, we simulated the effects of the thruster firings on melt and crystal composition in a directionally solidifying Sn-Bi alloy. The relative accelerations produced by the firings were simulated by impulsive accelerations of the same magnitude, duration and orientation as the requested firings. A comparison of the simulation results with the Seebeck signal indicates that there is a good agreement between the two. This unique opportunity allows us, for the first time, to quantitatively characterize actual g-jitter effects on an actual crystal growth experiment and to properly calibrate our models of g-jitter effects on crystal growth.

Favier, J.-J.; Iwan, J.; Alexander, D.; Garandet, J.-P.

1998-01-01

207

Study of Interesting Solidification Phenomena on the Ground and in Space (MEPHISTO)  

NASA Technical Reports Server (NTRS)

Real-time Seebeck voltage variations in a Sn-Bi melt during directional solidification in the MEPHISTO spaceflight experiment flown on the USMP-3 mission, have been correlated with well-characterized thruster firings and an Orbiter Main System (OMS) burn. The Seebeck voltage measurement is related to the response of the instantaneous average melt composition at the melt-crystal interface. This allowed us to make a direct comparison of numerical simulations with the experimentally obtained Seebeck signals. Based on the results of preflight and real-time computations, several well-defined thruster firing events were programmed to occur at specific times during the experiment. In particular, we simulated the effects of the thruster firings on melt and crystal composition in a directionally solidifying Sn-Bi alloy. The relative accelerations produced by the firings were simulated by impulsive accelerations of the same magnitude, duration and orientation as the requested firings. A comparison of the simulation results with the Seebeck signal indicates that there is a good agreement between the two. This unique opportunity allows us to make the first quantitative characterization of actual g-jitter effects on an actual crystal growth experiment and to calibrate our models of g-jitter effects on crystal growth.

Alexander, J. Iwan D.; Favier, J.-J.; Garandet, J.-P.

1999-01-01

208

Placebo Effect  

MedlinePLUS

... effect This information is current as of August 25, 2008 http://www.neurology.org/content/71/9/ ... effect This information is current as of August 25, 2008 Services Updated Information & http://www.neurology.org/ ...

209

Greenhouse Effect  

NSDL National Science Digital Library

This activity is a greenhouse-effect-in-a-bottle experiment. The lesson includes readings from NEED.org and an inquiry lab measuring the effect of carbon dioxide and temperature change in an enclosed environment.

Education, Connecticut E.

210

Effects of \\  

Microsoft Academic Search

Brainstorming instruction is an effective method for increasing the production of good ideas in a particular type of creative thinking problems, and is even more effective if preceded by extensive training in its use. (5 tables)

Sidney J. Parnes; Arnold Meadow

1959-01-01

211

Development of Flexible Micro-Thermo-electrochemical Generators Based on Ionic Liquids  

NASA Astrophysics Data System (ADS)

The unfavourable relationship between electrical and thermal conductivity limits the choice of solid-state materials for thermoelectric generators (TEG). Among ionic liquids (IOL), it appears that a large variety of thermoelectric (TE) materials with promising high Seebeck coefficients have potential for development. Furthermore, the novel solid-on-liquid deposition technology (SOLID) allows the encapsulation of liquid TE materials to create new, highly integrated TEG devices. Following this vision, this paper studies a large number of IOLs looking at TE-relevant parameters such as thermal and electrical conductivity, Seebeck coefficient and temperature-dependent viscosity. We show that positive and negative Seebeck coefficients can be obtained, depending on the molecular structure and the viscosity of the IOL. The properties of single-junction TEGs are presented in terms of I-V characteristics correlated with the IOL properties. We prove that the limiting effect of conversion efficiency is the current density that can be extracted from a device rather than the Seebeck coefficient.

Uhl, Stefanie; Laux, Edith; Journot, Tony; Jeandupeux, Laure; Charmet, Jérôme; Keppner, Herbert

2014-04-01

212

Doppler Effect  

NSDL National Science Digital Library

In this activity, learners use a tuning fork to explore how the Doppler effect works. They strike the tuning fork to produce a sound, then observe as the tone changes as the fork is swung back and forth. Learners also explore applications of the Doppler effect in technology.

Cosi

2009-01-01

213

Thermal Effects.  

ERIC Educational Resources Information Center

Presents a literature review of the effect of temperature on the biosphere water, covering publications of 1976-77. This review includes the effects of temperature on growth, production, and embryonic and larval development. A list of 401 references is also presented. (HM)

Talmage, Sylvia S.; Coutant, Charles C.

1978-01-01

214

Size effect  

Microsoft Academic Search

This paper surveys the available results on the size effect on the nominal strength of structures — a fundamental problem of considerable importance to concrete structures, geotechnical structures, geomechanics, arctic ice engineering, composite materials, etc., with applications ranging from structural engineering to the design of ships and aircraft. The history of the ideas on the size effect is briefly outlined

Zden?k P. Bažant

2000-01-01

215

Deterministic effects.  

PubMed

Deterministic effects are distinguished from stochastic effects for radiation protection purposes by the following characteristics: both incidence and severity increase as a function of dose after a threshold dose is reached. Cell killing is central to all deterministic effects with the exception of radiation-induced cataracts. The understanding of radiation-induced killing of cells has increased greatly in the last decade with an extraordinarily intense interest in apoptosis. Programmed cell death has long been known to developmental biologists and the importance of cell death has been recognized and quantified by tumor biologists and students of cell kinetics but the coining of a new name and the increase of understanding of the molecular aspects of cell death has stimulated interest. Some cells appear to be very sensitive to radiation and undergo apoptosis, whereas others such as fibroblasts do not with equal frequency. This characteristic, like many others, underlines the genetic differences among cell types. We are reaching a time that there are techniques and the knowledge to apply them to clinical and radiation protection problems. In radiotherapy, success depends on the differential effect between tumor and normal tissues that is obtained. To design the optimum therapy, a profile of both the tumor cells and the cells of the normal tissues that may be at risk would help. The profile would characterize the radiosensitivity and the underlying factors, which could help in the choice of adjunct therapy for tumor and normal tissue. Fibrosis, a common unwanted late effect, appears to be influenced by genetic factors, at least in experimental animals. Techniques are available for treating people as individuals more than ever before, and that must be a good thing to do. Protection against deterministic effects would seem an easy matter but we are uncomfortably ignorant of the precise effect of protracted low-dose irradiation on tissues, such as the bone marrow and the testis, important features of risk in space. Entering the new century, it may be timely to classify radiation effects, as Radiation Effects Research Foundation (RERF) has done, into cancer, genetic effects, and noncancer effects. The recognition in the atomic-bomb survivors of noncancer effects at doses on the order of 0.5 Sv (half the dose level considered a threshold in earlier studies) should stimulate interest in deterministic effects. PMID:11281201

Fry, R J

2001-04-01

216

Effective Schools Require Effective Principals  

ERIC Educational Resources Information Center

At long last, scholars and policy makers have come to realize what most school administrators have known for years--that effective schools require both outstanding teachers and strong leaders. Although there is considerable research about the characteristics of effective school leaders and the strategies principals can use to help manage…

LaPointe, Michelle; Davis, Stephen H.

2006-01-01

217

Doppler Effect  

NSDL National Science Digital Library

- The Doppler Effect explains why we hear a sonic boom when an airplane flies faster than the speed of sound. - Applying the Doppler Effect is how we have Doppler Radar used to track weather. - The Doppler Effect can be applied to outerspace and it evidence that the universe is expanding. Sound is energy traveling through a medium. A medium can be a gas, liquid, or solid. Therefore sound can not travel in outerspace since it is a vacuum which means there is nothing not even air. Energy traveling through a medium or even a vacuum is considered a wave. ...

Leet, Mr.

2008-03-16

218

Effect of Y doping on magnetic and transport properties of La0.7Sr0.3CoO3  

NASA Astrophysics Data System (ADS)

The temperature variation of magnetization, resistivity and thermo electric power of undoped and Y-doped La0.7Sr0.3CoO3 samples have been investigated. Y-doping decreases the magnetization possibly due to the spin state transition of Co-ions. The low temperature conduction in (La1-yYy)0.7Sr0.3CoO3 is consistent with the variable range hopping. With Y doping, value of the Seebeck coefficient increases, as Y doping decreases bandwidth and increases distortion.

Dwivedi, G. D.; Shukla, K. K.; Shahi, P.; Jha, O. K.; Ghosh, A. K.; Nigam, A. K.; Chatterjee, Sandip

2013-02-01

219

[Effective delegation].  

PubMed

Ninety-seven percent of middle level managers feel they face work overload. The source of this problem may lie in a failure to delegate tasks effectively. If a manager does not effectively delegate, he/she is more likely to report fatigue, stress and depression. Conversely, effectively delegating tasks will improve overall job quality, professional growth in subordinates and cooperation within the team. While it is necessary for managers to delegate tasks effectively, few can be considered to be good natural 'delegators'. Learning and training is necessary for managers to develop the necessary confidence and maturity. This article describes the definitions, purpose and benefits of delegation; factors related to effective delegation; strategies related to successful delegation and skills related to performing cross-cultural delegations. Such issues have seldom been addressed in previous articles. Moreover, nursing implications and suggested applications in nursing practice, education, management and research are mentioned. This article is intended to provide directions to nursing managers and subordinates to promote delegation knowledge and skills. PMID:19051179

Fang, Li; Hung, Chich-Hsiu

2008-12-01

220

Photoelectric Effect  

NSDL National Science Digital Library

This is a series of simulations of aspects of the photoelectric effect. There is an animation of the experiment with four choices of incident radiation - low and high intensity "red", to represent low energy light and low and high intensity "blue" to represent higher energy light. Electron production is animated and there is an ammeter to simulate current flow. Additional simulations show the effect of light frequency and intensity. There is a link to a spreadsheet that allows students to choose a sample from among five metals. The spreadsheet includes several questions to be answered after working through the materials.

221

Teapot Effect  

Microsoft Academic Search

When tea is poured from a teapot it often runs along the under side of the spout rather than falling into the cup. Recent experiments have shown that this ``teapot effect'' is not due to surface tension nor adhesion, as many have supposed. Therefore, a new explanation is presented which is based upon certain exact solutions of the hydrodynamic equations

Joseph B. Keller

1957-01-01

222

Coriolis Effect  

NSDL National Science Digital Library

This set of four animated slides illustrates the Coriolis effect, a manifestation of one of Newton's laws which says that objects move in a straight line, in an "inertial" frame of reference, unless acted upon by a force. The slides use the analogy of a ball thrown on a rotating carousel.

223

Effective Mentoring  

Microsoft Academic Search

Effective mentoring is essential to the growth and success of librarianship in all types of library. This paper considers the possibilities for fostering mentoring activities among early career librarians, mid-career transitional librarians, and non-professional library workers. First, the paper describes existing studies to illuminate the urgency of mentoring activities to address the diminishing number of librarians and changing librarianship in

Shin Freedman

2009-01-01

224

Slingshot Effect  

NSDL National Science Digital Library

This web page demonstrates the slingshot effect through a Flash simulation. The user places an object at some distance from Jupiter, sets up its initial velocity, then choose the appropriate time to lunch it. Once the simulation begins, the path of the projectile and its speed are shown.

Fowler, Michael; Ching, Jacquie H.

2008-09-20

225

System Effectiveness  

SciTech Connect

An effective risk assessment system is needed to address the threat posed by an active or passive insider who, acting alone or in collusion, could attempt diversion or theft of nuclear material. It is critical that a nuclear facility conduct a thorough self-assessment of the material protection, control, and accountability (MPC&A) system to evaluate system effectiveness. Self-assessment involves vulnerability analysis and performance testing of the MPC&A system. The process should lead to confirmation that mitigating features of the system effectively minimize the threat, or it could lead to the conclusion that system improvements or upgrades are necessary to achieve acceptable protection against the threat. Analysis of the MPC&A system is necessary to understand the limits and vulnerabilities of the system to internal threats. Self-assessment helps the facility be prepared to respond to internal threats and reduce the risk of theft or diversion of nuclear material. MSET is a self-assessment or inspection tool utilizing probabilistic risk assessment (PRA) methodology to calculate the system effectiveness of a nuclear facility's MPC&A system. MSET analyzes the effectiveness of an MPC&A system based on defined performance metrics for MPC&A functions based on U.S. and international best practices and regulations. A facility's MC&A system can be evaluated at a point in time and reevaluated after upgrades are implemented or after other system changes occur. The total system or specific subareas within the system can be evaluated. Areas of potential performance improvement or system upgrade can be assessed to determine where the most beneficial and cost-effective improvements should be made. Analyses of risk importance factors show that sustainability is essential for optimal performance. The analyses reveal where performance degradation has the greatest detrimental impact on total system risk and where performance improvements have the greatest reduction in system risk. The risk importance factors show the amount of risk reduction achievable with potential upgrades and the amount of risk reduction actually achieved after upgrades are completed. Applying the risk assessment tool gives support to budget prioritization by showing where budget support levels must be sustained for MC&A functions most important to risk. Results of the risk assessment are also useful in supporting funding justifications for system improvements that significantly reduce system risk.

Powell, Danny H [ORNL] [ORNL; Elwood Jr, Robert H [ORNL] [ORNL

2011-01-01

226

Effects of Synthesis Temperature on the Microstructure and Thermoelectric Properties of Te-Se Codoped Skutterudites  

NASA Astrophysics Data System (ADS)

Skutterudite compounds Co4Sb11.3Te0.5Se0.2 were synthesized by solid-state reaction at different temperatures (853 K, 903 K, 953 K, and 1003 K) with subsequent spark plasma sintering. x-Ray diffraction, field-emission scanning electron microscopy, and electron probe microanalysis were utilized to analyze the phase structure, microstructure, and actual compositions of the samples. The results showed that the actual composition and the grain size vary with the synthesis temperature. The thermoelectric properties of all samples were measured in the temperature range of 300 K to 800 K. As the synthesis temperature increases, the electrical conductivity increases rapidly, the absolute Seebeck coefficient falls, and the thermal conductivity first decreases and then increases. The highest dimensionless figure of merit ZT was achieved for the sample synthesized at 953 K, exceeding 1.0 at high temperature.

Ding, Shijie; Duan, Bo; Xu, Chenglong; Li, Yao; Liu, Lisheng; Zhai, Pengcheng

2013-10-01

227

Mass Fluctuation Effect in Ti1-x Nb x S2 Bulk Compounds  

NASA Astrophysics Data System (ADS)

The thermoelectric properties of Nb-substituted TiS2 compounds have been investigated in the temperature range of 300 K to 700 K. Polycrystalline samples in the series Ti1-x Nb x S2 with x varying from 0 to 0.05 were prepared using solid-liquid-vapor reaction and spark plasma sintering. Rietveld refinements of x-ray diffraction data are consistent with the existence of full solid solution for x ? 0.05. Transport measurements reveal that niobium can be considered as an electron donor when substituted at Ti sites. Consequently, the electrical resistivity and the absolute value of the Seebeck coefficient decrease as the Nb content increases, due to an increase in the carrier concentration. Moreover, due to mass fluctuation, the lattice thermal conductivity is reduced, leading to a slight increase of ZT values as compared with TiS2.

Beaumale, M.; Barbier, T.; Bréard, Y.; Raveau, B.; Kinemuchi, Y.; Funahashi, R.; Guilmeau, E.

2013-10-01

228

Effect of Biaxial Strain on Electronic and Thermoelectric Properties of Mg2Si  

NASA Astrophysics Data System (ADS)

The electronic and thermoelectric properties of biaxially strained magnesium silicide Mg2Si are analyzed by means of first-principle calculations and semiclassical Boltzmann theory. Electron and hole doping are examined for different doping concentrations and temperatures. Under strain the degeneracy of the electronic orbitals near the band edges is removed, the orbital bands are warped, and the energy gap closes up. These characteristics are rationalized in the light of the electron density transfers upon strain. The electrical conductivity increases with the biaxial strain, whereas neither the Seebeck coefficient nor the power factor (PF) follow this trend. Detailed analysis of the evolution of these thermoelectric properties is given in terms of the in-plane and cross-plane components. Interestingly, the maximum value of the PF is shifted towards lower temperatures when increasingly intensive strain is applied.

Balout, Hilal; Boulet, Pascal; Record, Marie-Christine

2013-12-01

229

Effects of Synthesis Temperature on the Microstructure and Thermoelectric Properties of Te-Se Codoped Skutterudites  

NASA Astrophysics Data System (ADS)

Skutterudite compounds Co4Sb11.3Te0.5Se0.2 were synthesized by solid-state reaction at different temperatures (853 K, 903 K, 953 K, and 1003 K) with subsequent spark plasma sintering. x-Ray diffraction, field-emission scanning electron microscopy, and electron probe microanalysis were utilized to analyze the phase structure, microstructure, and actual compositions of the samples. The results showed that the actual composition and the grain size vary with the synthesis temperature. The thermoelectric properties of all samples were measured in the temperature range of 300 K to 800 K. As the synthesis temperature increases, the electrical conductivity increases rapidly, the absolute Seebeck coefficient falls, and the thermal conductivity first decreases and then increases. The highest dimensionless figure of merit ZT was achieved for the sample synthesized at 953 K, exceeding 1.0 at high temperature.

Ding, Shijie; Duan, Bo; Xu, Chenglong; Li, Yao; Liu, Lisheng; Zhai, Pengcheng

2014-06-01

230

Effective Presentations  

PubMed Central

Where the purpose of presentations is to inform, effective delivery is important to ensure that audiences receive the educational message. We offer six suggestions: introduce the topic in an interesting way; speak loudly enough; do not read; involve the audience actively; respect the attention span of the audience; and limit the amount of content. We conclude that the skills of live public presentation can be learned, but that the art of presentation is innate. Imagesp2063-ap2064-a

Spooner, H. James; Swanson, Richard W.

1990-01-01

231

Compton Effect  

NSDL National Science Digital Library

The Compton Effect model simulates the the scattering of light off of an electron, the Compton effect. Compton used the idea that light behaves like a particle to explain light-electron (photon-electron) scattering. He used the relation for the energy and momentum of the photon and the relativistic expression for the energy of the electron, and applied relativistic energy and momentum conservation for the collision. The wavelength shift of the light depend on the angle of the scattered photon (and the electron). By changing the scattering angle in the simulation, the angle of the scattered photon changes according to Compton's equation. The panel on the left shows the experimental set up, while the panel on the right shows the resulting photon wavelength from the scattering. In a typical Compton experiment, light is scattered off of the electrons in an atom, and there is little scattering due to the more tightly held electrons while there is more scattering due to the less tightly held electrons. This is what is responsible for the two peak distribution shown. The Compton Effect model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_qm_compton.jar file will run the program if Java is installed.

Palop, Jose I.

2010-12-12

232

Ag and Cu doping and their effects on the thermoelectric properties of ?-Zn4Sb3  

NASA Astrophysics Data System (ADS)

The measurements of electrical resistivity and Seebeck coefficients of Ag- and Cu-doped compounds ?-(Zn1-xMx)4Sb3 (M=Ag,Cu;x=0,0.0025,0.005,0.01) were carried out, and the results indicated that both their resistivity and Seebeck coefficients increase first ( x?0.0025 for Ag and x?0.005 for Cu) and then decrease obviously with further increase in their doping content. Correspondingly, hole concentration behaviors in the opposite way. In terms of the one vacancy-two interstitial Zn atom model: A11BCSb10 and two-vacancy-three-interstitial Zn atom model: A10BCDSb10 (here A is normal Zn atom and B, C, and D interstitial Zn atoms) proposed by Cargnoni [Chem. Eur. J. 10, 3861 (2004)]10.1002/chem.200400327, first-principles calculations were performed on the occupation options of Ag and Cu atoms in disordered ?-Zn4Sb3 . The results indicated that both Ag and Cu atoms occupy preferentially the Zn vacancies in normal sites. Subsequently, Ag and Cu atoms will substitute for interstitial atoms D (for Ag) and B (for Cu). The calculations also showed that as Ag and Cu atoms fill Zn vacancies they play the role of donors, leading to a decrease in hole concentration; while Ag and Cu atoms replace the interstitial atoms they act as acceptors resulting in an increase in hole concentration, which are in good agreement with the nonmonotonous change behavior in the transport properties and Hall carrier concentrations observed experimentally. In addition, calculations revealed that Cu instead of Ag can also fill the Zn vacancies with smaller volumes and Cu doping nearly always has lower formation energies than Ag, which could give a reasonable explanation for the higher solubility of Cu than that of Ag in ?-Zn4Sb3 .

Liu, Mian; Qin, Xiaoying; Liu, Changsong; Pan, Lin; Xin, Hongxing

2010-06-01

233

Effect of varying mixture ratio of raw material powders on the thermoelectric properties of AlMgB14-based materials prepared by spark plasma sintering  

NASA Astrophysics Data System (ADS)

Thermoelectric properties of AlMgB14-based materials prepared by spark plasma sintering were investigated. Al, Mg, and B powders were used as raw material powders. The raw powders were mixed using a V-shaped mixer, and then the mixture was sintered at 1673 K or 1773 K. The mixture ratio of raw powders was varied around stoichiometric ratio of AlMgB14. X-ray diffraction patterns of samples showed that all samples consist of AlMgB14 and MgAl2O4. The Seebeck coefficient of the samples exhibited significant change depending on the varying mixture ratio and sintering temperature. One sample exhibited a large negative value for the Seebeck coefficient (approximately -500 ?V/K) in the temperature range from 573 K to 1073 K, while others showed positive value (250-450 ?V/K). Thus n-type AlMgB14-based material has been realized by varying raw material ratio and sintering temperature.

Miura, Shota; Sasaki, Hikaru; Takagi, Ken-ichi; Fujima, Takuya

2014-08-01

234

Spin caloritronics.  

PubMed

Spintronics is about the coupled electron spin and charge transport in condensed-matter structures and devices. The recently invigorated field of spin caloritronics focuses on the interaction of spins with heat currents, motivated by newly discovered physical effects and strategies to improve existing thermoelectric devices. Here we give an overview of our understanding and the experimental state-of-the-art concerning the coupling of spin, charge and heat currents in magnetic thin films and nanostructures. Known phenomena are classified either as independent electron (such as spin-dependent Seebeck) effects in metals that can be understood by a model of two parallel spin-transport channels with different thermoelectric properties, or as collective (such as spin Seebeck) effects, caused by spin waves, that also exist in insulating ferromagnets. The search to find applications--for example heat sensors and waste heat recyclers--is on. PMID:22522639

Bauer, Gerrit E W; Saitoh, Eiji; van Wees, Bart J

2012-05-01

235

Microbial effects  

SciTech Connect

The postulated doubling of atmospheric CO/sub 2/ is not likely to have direct effect on soil microbial activity because during the growing season, the concentration of CO/sub 2/ in the soil atmosphere is already ten to fifty times higher than existing atmospheric CO/sub 2/. Based on all available experimental information, it is estimated that a doubling of atmospheric CO/sub 2/ will cause an increase in primary productivity of 10 to 40% depending on locale. The increase in biomass will, in turn, produce a limitation of available soil nutrients, especially nitrogen and phosphorus. Increased organic carbon together with nitrogen and/or phosphorus limitation will result in a preferential increase in nitrogen fixation and mycorrhizal activities as the expedient means for supplying required nutrients to sustain the predicted increase in primary productivity. Therefore, increased emphasis should be placed on fundamental research related to soil microbiology with special reference to nitrogen-fixing, nitrifying and denitrifying bacteria, and to the mycorrhizal fungi. 111 references, 2 figures.

Lamborg, M.R.; Hardy, R.W.F.; Paul, E.A.

1983-01-01

236

Nanocubes  

NASA Astrophysics Data System (ADS)

A giant Seebeck coefficient of -890 ?V/K at 500 °C has been observed in Y0.2Sr0.8TiO3 prepared using nanocubes. Doping rare earth elements, RE, has revealed that small RE is effective to enhance the Seebeck coefficient. Through soft mode observations by Raman spectroscopy and structural calculations based on density functional theory, it has been found that the breakdown of inversion symmetry of the perovskite structure near the surface of nanocubes can be recovered by doping with small RE. Because the dielectric constant is strongly related to the surface structure in this compound, we suggest that RE doping modulates the potential barrier at the grain boundary, resulting in a pronounced energy filtering effect in Y doped SrTiO3.

Kinemuchi, Yoshiaki; Mimura, Ken-ichi; Towata, Atsuya; Kato, Kazumi

2014-06-01

237

Lanthanide Contraction Effect In Magnetic Thermoelectric Materials Of Rare Earth-doped Bi1.5Pb0.5Ca2Co2O8  

NASA Astrophysics Data System (ADS)

We report in this paper the result of synthesis and crystal structure characterization of magnetic thermoelectric materials of rare-earth-doped Bi1.5Pb0.5Ca2Co2O8, namely Bi1.5Pb0.5Ca1.9RE0.1Co2O8 (RE = La, Pr, Sm, Eu, Gd, Ho). Single phase samples have been prepared by solid state reaction process using precursors of Bi2O3, PbO, CaCO3, RE2O3, and Co3O4. The precursors were pulverized, calcinated, and sintered in air at various temperatures for several hours. Analysis of XRD data shows that Bi1.5Pb0.5Ca1.9RE0.1Co2O8 compound is a layered system consisting of an alternate stack of CoO2 layer and Bi2Sr2O4 block along the c-axis. The misfit structure along b-direction is revealed from the difference of the b-axis length belonging to two sublattices, namely hexagonal CdI2-type CoO2 layer and rock-salt (RS) NaCl-type Bi2Sr2O4 block, while they possess the common a- and c-axis lattice parameters and ? angles. The overall crystal structure parameters (a, b, and c) increases with type of doping from La to Ho, namely by decreasing the ionic radii of rare-earth ion. We discuss this phenomenon in terms of the lanthanide contraction, an effect commonly found in the rare-earth compound, results from poor shielding of nuclear charge by 4f electrons. In addition, the values of b-lattice parameters in these rare-earth doped samples are almost the same with those belongs to undoped parent compound (Bi1.5Pb0.5Sr2Co2O8) and its related Y-doped (Bi1.5Pb0.5Ca1.9Y0.1Co2O8) samples, while the c-values reduced significantly in rare-earth doped samples, with opposite trend with those of variation of a-axis length. Morevover, the misfit degree in rare-earth doped compound is higher in compared to parent compound and Y-doped samples. We argue that these structural changes induced by rare-earth doping may provide information for the variation of electronic structure of Co-ions (Co3+ and Co4+), in particular their different spin states of low-spin, intermediate-spin, and high-spin. This, in turn, will affect the thermoelectric properties (Seebeck coefficient) of the system.

Sutjahja, Inge Magdalena; Akbar, Taufik; Nugroho, Agung

2010-12-01

238

Effect of Addition of Ag, In or Pb on the Structure and Thermoelectric Performance of ?-Zn4Sb3  

NASA Astrophysics Data System (ADS)

Zn4Sb3 bulk alloys with addition of Ag, Pb or In were prepared by high- frequency induction melting and post-annealing. X-ray powder diffraction analysis showed that the lattice of the compound was distorted by the additions. Differential scanning calorimetry analysis revealed that the phase transition from ? to ? or ? to ?' was suppressed by the addition of In or Ag. A high carrier concentration and high thermal conductivity were found in the sample with Ag or In additions. However, lower electric resistivity, nearly the same Seebeck coefficient, and low thermal conductivity, as compared with the undoped sample, were found in the sample with Pb addition, leading to good thermoelectric performance. The highest ZT value of 1.12 at 605 K was achieved for the Pb0.02Zn4Sb3 sample in this work, which is about 30% larger than that for the undoped ?-Zn4Sb3.

Liu, F. S.; Pan, L. C.; Ao, W. Q.; He, L. P.; Li, X. X.; Li, H. T.; Li, J. Q.

2012-08-01

239

Effect of nanocomposite structure on the thermoelectric properties of 0.7-at% Bi-doped Mg2Si nanocomposite  

NASA Astrophysics Data System (ADS)

Nanocomposites offer a promising approach to the incorporation of nanostructured constituents into bulk thermoelectric materials. The 0.7-at% Bi-doped Mg2Si nanocomposites are prepared by spark plasma sintering of the mixture of nanoscale and microsized 0.7-at% Bi-doped Mg2Si powders. Microstructure analysis shows that the bulk material is composed of nano- and micrograins. Although the nanograin hinders electrical conduction, the nanocomposite structure is more helpful to reduce thermal conductivity and increase the Seebeck coefficient, hence improving thermoelectric performance. A dimensionless figure of merit of 0.8 is obtained for the 0.7-at% Bi-doped Mg2Si nanocomposite with 50-wt % nanopowder, which is about twice larger than that of the sample without nanopowder.

Yang, Mei-Jun; Shen, Qiang; Zhang, Lian-Meng

2011-10-01

240

Design, Calibration, and Testing of a New Tian-Calvet Heat-Flow Microcalorimeter for Measurement of Differential Heats of Adsorption  

Microsoft Academic Search

A Tian-Calvet heat-flow microcalorimeter system is described for measurement of heats of adsorption and reaction on porous solids. Heat-flow signals are measured in transducer assemblies consisting of several hundred Seebeck-effect thermoelements connected in series and arranged in a square configuration. These transducers surround a stainless steel calorimeter cell connected to a high-vacuum volumetric adsorption system. The sensitivity of the calorimeter

V. Garcia-Cuello; J. C. Moreno-Pirajan; L. Giraldo-Gutierrez; K. Sapag; G. Zgrablich

2008-01-01

241

Mechanism of the Electrical Conduction in Li-Doped NiO  

Microsoft Academic Search

The electrical conductivity and the Seebeck effect are measured in the temperature region of 100 to 1300°K in NiO doped with Li. From the results it is concluded that the mobility of the charge carriers involves no activation energy. The temperature dependence of the conductivity is almost completely determined by the charge-carrier concentration. In order to calculate from the measurements

A. J. Bosman; C. Crevecoeur

1966-01-01

242

Thermoelectric properties of p-type antimony bismuth telluride alloys prepared by cold pressing  

Microsoft Academic Search

Sb2 ? xBixTe3 (x = 0.43–0.51) thermoelectric materials were prepared by the powder metallurgy method. The effects of grinding and sintering processes on the Seebeck coefficient, electrical conductivity, and thermoelectric figure of merit were investigated. For different particle sizes, a shift in maximum of Z = f(x) dependence was found. This shift can be explained by the presence of point

J. Navrátil; Z. Starý

1996-01-01

243

Electrical properties of the 85% Bi 2Te 3-15% Bi 2Se 3 thermoelectric material doped with SbI 3 and CuBr  

Microsoft Academic Search

The temperature dependences of the Seebeck coefficient, resistivity, Hall coefficient, and carrier mobility of SbI3- and CuBr-doped 85% Bi2Te3-15% Bi2Se3 single crystals have been characterized at temperatures ranging from 77 to 600 K, and the degenerate temperature, scattering parameter, bandgap energy, and the effective masses of the electron and hole have been determined. The degenerate temperature of the 85% Bi2Te3-15%

D. B. Hyun; J. S. Hwang; T. S. Oh; J. D. Shim; N. V. Kolomoets

1998-01-01

244

Rapid synthesis of high thermoelectric performance higher manganese silicide with in-situ formed nano-phase of MnSi  

Microsoft Academic Search

P-type higher manganese silicides with in-situ formed nano-MnSi phase were prepared by a rapid melt-spinning process combined with a spark plasma sintering method (MS-SPS). Because of the in-situ formed multi-scale nano-MnSi phase, the electrical conductivity of the samples increases dramatically while the Seebeck coefficient maintains relatively high values owing possibly to an energy filtering effect. The thermal conductivity of the

Wenhui Luo; Han Li; Yonggao Yan; Zebing Lin; Xinfeng Tang; Qinjie Zhang; Ctirad Uher

2011-01-01

245

Studies on transport properties of MoSe2-xTex single crystals  

NASA Astrophysics Data System (ADS)

Single crystals of MoSe2-xTex (x = 0.25, 0.5, 1, 1.5, 1.75) were grown by chemical vapor transport technique. The stoichiometric composition of grown crystals was confirmed by energy dispersive X-ray spectroscopy. Transport properties like electrical resistivity, Seebeck co-efficient measurements at high temperature and Hall effect at room temperature were studied on these samples. The obtained results are discussed in details in this paper.

Bhavsar, Divyesh N.; Jani, Ashvinkumar R.

2013-08-01

246

Thermoelectric Properties of Layered Anisotropic p-type PbSb2Te4 Compound and Peculiarities of its Energy Spectrum  

Microsoft Academic Search

The measurements of the transport tensors: electrical ?11, ?33 and thermal ?11, ?33 conductivity, Seebeck S11, S33 and Hall effect R123, R321 (11 - along the cleavage plane and 33 - along the trigonal crystal axis) have been made on the high- quality single crystals of the ternary layered p-type PbSb2Te4 compound in the temperature range 85-350 K. These crystals

L. E. Shelimova; M. K. Zhitinskaya; S. A. Nemov; T. E. Svechnikova; P. P. Konstantinov; E. S. Avilov; M. A. Kretova; V. S. Zemskov

247

Twoband model of the electron spectrum in n-Bi2Te2.7Se0.3  

Microsoft Academic Search

The Hall factor and thermoelectric properties of n-Bi2Te2.7Se0.3 solid solution with the room-temperature Seebeck coefficient S = 212 ?V\\/K have been studied in the temperature range 77-350 K. The observed temperature dependences demonstrate some specific features, which were found earlier in samples with lower electron density N. The effect of these specific features on the thermoelectric figure of merit Z

P. P. Konstantinov; L. V. Prokofieva; M. I. Fedorov; D. A. Pshenay-Severin; Yu. I. Ravich; V. V. Kompaniets; V. A. Chistyakov

2005-01-01

248

Effective Teaching/Effective Urban Teaching  

ERIC Educational Resources Information Center

This article considers the ways in which 17 novice teachers define and describe effective urban teaching and the stark contrasts that these teachers draw between effective urban teaching and effective teaching. The authors find that descriptions of students played a considerable role when participants made distinctions between effective teaching…

Watson, Dyan; Charner-Laird, Megin; Kirkpatrick, Cheryl L.; Szczesiul, Stacy Agee; Gordon, Pamela J.

2006-01-01

249

Effect of Ce-Doping on Thermoelectric Properties in PbTe Alloys Prepared by Spark Plasma Sintering  

NASA Astrophysics Data System (ADS)

Ce-doped Pb1- x Ce x Te alloys with x = 0, 0.005, 0.01, 0.015, 0.03, and 0.05 were prepared by induction melting, ball milling, and spark plasma sintering techniques. The structure and thermoelectric properties of the samples were investigated. X-ray diffraction (XRD) analysis indicated that the samples were of single phase with NaCl-type structure for x less than 0.03. The lattice parameter a increases with increasing Ce content. The lower Ce-doped samples ( x = 0.005 and 0.01) showed p-type conduction, whereas the pure PbTe and the higher doped samples ( x = 0, 0.015, 0.03, and 0.05) showed n-type conduction. The lower Ce-doped samples exhibited a much higher absolute Seebeck coefficient, but the higher electrical resistivity and higher thermal conductivity compared with pure PbTe resulted in a lower figure of merit ZT. In contrast, the higher Ce-doped samples exhibited a lower electrical resistivity, together with a lower absolute Seebeck coefficient and comparable thermal conductivity, leading to ZT comparable to that of PbTe. The lowest thermal conductivity (range from 0.99 W m-1 K-1 at 300 K to 0.696 W m-1 K-1 at 473 K) was found in the alloy Pb0.95Ce0.05Te due to the presence of the secondary phases, leading to a ZT higher than that of pure PbTe above 500 K. The maximum figure of merit ZT, in the alloy Pb0.95Ce0.05Te, was 0.88 at 673 K.

Li, J. Q.; Li, S. P.; Wang, Q. B.; Wang, L.; Liu, F. S.; Ao, W. Q.

2011-10-01

250

Alloys Fabricated by Gas Atomization and Hot Extrusion  

NASA Astrophysics Data System (ADS)

In this research, n-type (Bi2Te3)1- x (Bi2Se3) x -based thermoelectric (TE) materials were produced through a gas atomization process, and subsequently hot extruded with an extrusion ratio of 10:1 at 400 °C. The effect of chemical composition on TE properties was investigated. The microstructure of all extruded bars showed a homogeneous and fine distribution of grains due to the dynamic recrystallization during the hot extrusion process. With increasing Bi2Te3 content, from 0.85 to 0.90, both electrical resistivity and Seebeck coefficient values were increased. The maximum figure of merit ( ZT) 0.673 was obtained at room temperature for (Bi2Te3)0.90(Bi2Se3)0.10 alloys due to them exhibiting higher seebeck coefficient and lower thermal conductivity than other compositions.

Madavali, Babu; Kim, Hyo-Seob; Hong, Soon-Jik

2014-06-01

251

Thermoelectric Properties and n- to p-Type Conversion of Co-Doped ZrNiSn-Based Half-Heusler Alloys  

NASA Astrophysics Data System (ADS)

Half-Heulser thermoelectric materials ZrNi1- y Co y Sn ( y = 0, 0.02, 0.04, 0.08, 0.12) were prepared by a time-efficient levitation melting and spark plasma sintering procedure. X-ray diffraction analysis and electron probe microanalysis showed that single-phase half-Heusler compounds without compositional segregation have been obtained. The effects of Co doping on the electrical conductivity, Seebeck coefficient, and thermal conductivity of ZrNiSn-based half-Heusler alloys have been investigated from 300 K to 900 K. The Seebeck coefficient displayed a change from negative to positive values above nominal Co doping content of y = 0.02, indicating a transition in the conduction behavior from n-type to p-type. The maximum dimensionless figure of merit ZT of undoped ZrNiSn sample reached 0.5 at 870 K.

Xie, Han-Hui; Yu, Cui; He, Bin; Zhu, Tie-Jun; Zhao, Xin-Bing

2012-06-01

252

High temperature transport properties of thermoelectric CaMnO3-? — Indication of strongly interacting small polarons  

NASA Astrophysics Data System (ADS)

The conductivity and Seebeck coefficient of CaMnO3-? have been studied at temperatures up to 1000 °C and in atmospheres with controlled oxygen partial pressure. Both transport coefficients were varied in situ by the reversible formation of oxygen vacancies up to ? = 0.15. The charge carrier concentration was calculated using a defect chemical model. The Seebeck coefficient could be approximated by Heikes' formula, while the conductivity shows a maximum at a molar charge carrier concentration of 0.25. These results were interpreted as a signature of strong electronic correlation effects, and it was concluded that charge transport in CaMnO3-? occurs via strongly interacting small polarons. General prospects for strongly correlated materials as potential candidates for high temperature thermoelectric power generation were discussed.

Schrade, M.; Kabir, R.; Li, S.; Norby, T.; Finstad, T. G.

2014-03-01

253

Measurement of Thermopower and Current-Voltage Characteristics of Molecular Junctions to Identify Orbital Alignment  

SciTech Connect

We report an experimental technique that concurrently measures the Seebeck coefficient and the current-voltage (I-V) characteristics of a molecular junction to determine the identity and the effective energetic separation of the molecular orbital closest to the electrodes’ Fermi level. Junctions created by contacting a gold-coated atomic force microscope tip with a monolayer of molecules assembled on a gold substrate were found to have a Seebeck coefficient of (+16.9±1.4) ?V/K. This positive value unambiguously shows that the highest occupied molecular orbital (HOMO) dominates charge transport. Further, by analyzing the (I-V) characteristics, the HOMO level is estimated to be ? 0.69?eV with respect to the Fermi level.

Tan, Aaron; Sadat, Seid; Reddy, Pramod

2010-01-01

254

Phase purity and the thermoelectric properties of Ge2Sb2Te5 films down to 25 nm thickness  

NASA Astrophysics Data System (ADS)

Thermoelectric phenomena strongly influence the behavior of chalcogenide materials in nanoelectronic devices including phase-change memory cells. This work uses a novel silicon-on-insulator experimental structure to measure the phase and temperature-dependent Seebeck and Thomson coefficients of Ge2Sb2Te5 films including the first data for films of thickness down to 25 nm. The Ge2Sb2Te5 films annealed at different temperatures contain varying fractions of the amorphous and crystalline phases which strongly influence the thermoelectric properties. The Seebeck coefficient reduces from 371 ?V/K to 206 ?V/K as the crystalline fraction increases by a factor of four as quantified using x-ray diffraction. The data are consistent with modeling based on effective medium theory and suggest that careful consideration of phase purity is needed to account for thermoelectric transport in phase change memory.

Lee, Jaeho; Kodama, Takashi; Won, Yoonjin; Asheghi, Mehdi; Goodson, Kenneth E.

2012-07-01

255

Thermoelectricity of Nanocomposites Containing TiO2–CoO Coaxial Nanocables  

SciTech Connect

TiO{sub 2}-CoO coaxial nanocables were deposited into anodic aluminum oxide (AAO) nanoporous templates to form nanocomposite materials. Electron microscopic analysis was conducted to reveal their structures. Seebeck coefficients of the composites were measured. The highest absolute value of Seebeck coefficient is 393 {micro}V K{sup -1} for the TiO{sub 2} nanotube-filled AAO. The TiO{sub 2}-CoO coaxial nanocable-filled AAO has a lower absolute value of 300 {micro}V K{sup -1}. Both composites showed n-type behavior. The effect of Ag nanoparticles addition on the thermoelectric behavior was also examined.

Su, L.; Zhang, L.; Gana, Y.X.

2011-04-01

256

The central role of the Peltier coefficient in thermoelectric cooling  

NASA Astrophysics Data System (ADS)

This paper discusses the special role that the Peltier effect plays in thermoelectric cooling. From a particular energy balance for a thermocouple, we can conclude that the Peltier component pumps out the energy of all other terms: Joule, Fourier, Seebeck, and thermoelectric cooling. We emphasize also that in this energy balance, there is a need to include a new contribution, named after Seebeck that usually is not considered in the literature. We discuss a new method to evaluate the Peltier coefficient using measurements of the two temperature gradients at the junction of a thermocouple. An arrangement has been built to explore this method. A precise value for the Peltier coefficient of a thermocouple has been obtained but which deviates from the Kelvin relation. A better design of the experimental device is needed.

Garrido, J.; Casanovas, A.

2014-03-01

257

Insights on the origin of the structural phase transition in BaV{sub 10}O{sub 15} from electronic structure calculations and the effect of Ti-doping on its structure and electrical transport properties  

SciTech Connect

Band structure calculations at the level of LMTO-ASA provide insight into the electronic structure of BaV{sub 10}O{sub 15} and the origin of the structural phase transition. A crystal orbital Hamiltonian population/integrated crystal orbital Hamiltonian population analysis provides evidence that the crystallographic phase transition is driven by V-V bond formation. As well, the energy bands near the Fermi level are very narrow, <1eV, consistent with the fact that the observed insulating behavior can be due to electron localization via either Mott-Hubbard correlation and/or Anderson disorder. The partial solid solution, BaV{sub 10-x}Ti{sub x}O{sub 15}, was examined to study the effect of Ti-doping at the V sites on the structure and electronic transport properties. In spite of the non-existence of 'BaTi{sub 10}O{sub 15}', the limiting x=8, as indicated by a monotonic increase in the cell volume and systematic changes in properties. This limit may be due to the difficulty of stabilizing Ti{sup 2+} in this structure. For x=0.5 both the first order structural phase transition and the magnetic transition at 40K are quenched. The samples obey the Curie-Weiss law to x=3 with nearly spin only effective moments along with {theta} values which range from -1090K (x=0.5) to -1629K (x=3). For x>3 a very large, {approx}2x10{sup -3}emu/mol, temperature independent (TIP) contribution dominates. Conductivity measurements on sintered, polycrystalline samples show semiconducting behavior for all compositions. Activation energies for Mott hopping derived from high temperature data range from {approx}0.1eV for x=0-1 and fall to a plateau of 0.06eV for x=3-7. Low temperature data for x=3, 5 and 7 show evidence for Mott variable range hoping (VRH) with a T1/4 law and in one case between 5 and 17K, a Efros-Shklovskii correlated hopping, T1/2 law, was seen, in sharp contrast to BaV{sub 10}O{sub 15} where only the E-S law was observed up to 75K. Seebeck coefficients are small (<35{mu}V/K), positive, roughly TIP and increase with increasing x up to x=5. This may point to a Heikes hopping of holes but a simple single carrier model is impossible. The compositions for x>3 are remarkable in that local moment behavior is lost, yet a metallic state is not reached. The failure of this system to be driven metallic even at such high doping levels is not fully understood but it seems clear that disorder induced carrier localization plays a major role.

Bridges, C.A. [Department of Chemistry and Brockhouse Institute for Materials Research, McMaster University, 1280 Main Street W. (ABB-424), Hamilton, Ontario, L8S 4M1 (Canada); Greedan, J.E. [Department of Chemistry and Brockhouse Institute for Materials Research, McMaster University, 1280 Main Street W. (ABB-424), Hamilton, Ontario, L8S 4M1 (Canada)]. E-mail: greedan@mcmaster.ca; Kleinke, Holger [Department of Chemistry, University of Waterloo, Waterloo, Ontario (Canada)

2004-12-01

258

Cross-plane electrical and thermal transport in oxide metal/semiconductor superlattices  

NASA Astrophysics Data System (ADS)

Perovskite oxides display a rich variety of electronic properties as metals, ferroelectrics, ferromagnetics, multiferroics, and thermoelectrics. Cross-plane electron filtering transport in metal/semiconductor superlattices provides a potential approach to increase the thermoelectric figure of merit (ZT). La0.67Sr0.33MnO3 (LSMO) and LaMnO3 (LMO) thin-film depositions were optimized using pulsed laser deposition (PLD) to achieve low resistivity constituent materials for LSMO/LMO superlattice heterostructures on (100)-strontium titanate (STO) substrates. X-ray diffraction and high-resolution reciprocal space mapping (RSM) indicate that the superlattices are epitaxial and pseudomorphic. Cross-plane devices were fabricated by etching cylindrical pillar structures in superlattices using inductively-coupled-plasma reactive-ion etching. The cross-plane electrical conductivity data for LSMO/LMO superlattices reveal an effective barrier height of 220 meV. The cross-plane LSMO/LMO superlattices showed a giant Seebeck coefficient of 2560 microV/K at 300K that increases to 16640 microV/K at 360K. The large Seebeck coefficient may arise due to hot electron and spin filtering as LSMO/LMO superlattice constituent materials exhibit spintronic properties where charges and spin current are intertwined and can generate a spin-Seebeck effect. The room temperature thermal conductivity achieved in low resistivity superlattices was 0.92 W/mK, which indicates that cross-plane phonon scattering at interfaces reduces the lattice contribution to the thermal conductivity. The giant contribution of spin-Seebeck, the large temperature dependence of the cross-plane power factor, and the low thermal conductivity in low resistance LSMO/LMO superlattices may offer opportunities to realize spin-magnetic thermoelectric devices, and suggests a direction for further investigations of the potential of LSMO/LMO oxide superlattices for thermoelectric devices.

Jha, Pankaj

259

Thermoelectric Properties of Magnesium Silicide Deposited by Use of an Atmospheric Plasma Thermal Spray  

NASA Astrophysics Data System (ADS)

The thermoelectric properties of magnesium silicide (Mg2Si) samples prepared by use of an atmospheric plasma spray (APS) were compared with those of samples prepared from the same feedstock powder by use of the conventional hot-pressing method. The characterization performed included measurement of thermal conductivity, electrical conductivity, Seebeck coefficient, and figure of merit, ZT. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive x-ray spectroscopy (EDX) were used to assess how phase and microstructure affected the thermoelectric properties of the samples. Hall effect measurements furnished carrier concentration, and measurement of Hall mobility provided further insight into electrical conductivity and Seebeck coefficient. Low temperature and high velocity APS using an internal-powder distribution system achieved a phase of composition similar to that of the feedstock powder. Thermal spraying was demonstrated in this work to be an effective means of reducing the thermal conductivity of Mg2Si; this may be because of pores and cracks in the sprayed sample. Vacuum-annealed APS samples were found to have very high Seebeck coefficients. To further improve the figure of merit, carrier concentration must be adjusted and carrier mobility must be enhanced.

Fu, Gaosheng; Zuo, Lei; Longtin, Jon; Nie, Chao; Chen, Yikai; Tewolde, Mahder; Sampath, Sanjay

2014-07-01

260

Thermoelectric Properties of Magnesium Silicide Deposited by Use of an Atmospheric Plasma Thermal Spray  

NASA Astrophysics Data System (ADS)

The thermoelectric properties of magnesium silicide (Mg2Si) samples prepared by use of an atmospheric plasma spray (APS) were compared with those of samples prepared from the same feedstock powder by use of the conventional hot-pressing method. The characterization performed included measurement of thermal conductivity, electrical conductivity, Seebeck coefficient, and figure of merit, ZT. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive x-ray spectroscopy (EDX) were used to assess how phase and microstructure affected the thermoelectric properties of the samples. Hall effect measurements furnished carrier concentration, and measurement of Hall mobility provided further insight into electrical conductivity and Seebeck coefficient. Low temperature and high velocity APS using an internal-powder distribution system achieved a phase of composition similar to that of the feedstock powder. Thermal spraying was demonstrated in this work to be an effective means of reducing the thermal conductivity of Mg2Si; this may be because of pores and cracks in the sprayed sample. Vacuum-annealed APS samples were found to have very high Seebeck coefficients. To further improve the figure of merit, carrier concentration must be adjusted and carrier mobility must be enhanced.

Fu, Gaosheng; Zuo, Lei; Longtin, Jon; Nie, Chao; Chen, Yikai; Tewolde, Mahder; Sampath, Sanjay

2014-04-01

261

Communicating Effectively PDF  

Cancer.gov

Effective communication is essential for the delivery of quality cancer palliative care. And yet, healthcare providers often lack the skills to communicate effectively with their patients and families.

262

Deposition and investigation of lanthanum-cerium hexaboride thin films  

SciTech Connect

Thin films of lanthanum-cerium hexaboride, the promising thermoelectric material for low-temperature applications, are deposited on various substrates by the electron-beam evaporation, pulsed laser deposition and magnetron sputtering. The influence of the deposition conditions on the films X-ray characteristics, composition, microstructure and physical properties, such as the resistivity and Seebeck coefficient, is studied. The preferred (100) orientation of all films is obtained from XRD traces. In the range of 780-800 deg. C deposition temperature the highest intensity of diffractions peaks and the highest degree of the preferred orientation are observed. The temperature dependence of the resistivity and the Seebeck coefficient of films are investigated in the temperature range of 4-300 K. The features appropriate to Kondo effect in the dependences {rho}(T) and S(T) are detected at temperatures below 20 K. Interplay between the value of the Seebeck coefficient, metallic parameters and Kondo scattering of investigated films is discussed. - Graphical abstract: Kondo scattering in (La,Ce)B{sub 6} films: temperature dependence of the resistivity of (La,Ce)B{sub 6} films on various substrates and the ceramics La{sub 0.99}Ce{sub 0.01}B{sub 6}.

Kuzanyan, A.S. [Institute for Physical Research NAS, Ashtarak, 378410 (Armenia)]. E-mail: akuzan@ipr.sci.am; Harutyunyan, S.R. [Institute for Physical Research NAS, Ashtarak, 378410 (Armenia); Vardanyan, V.O. [Institute for Physical Research NAS, Ashtarak, 378410 (Armenia); Badalyan, G.R. [Institute for Physical Research NAS, Ashtarak, 378410 (Armenia); Petrosyan, V.A. [Institute for Physical Research NAS, Ashtarak, 378410 (Armenia); Kuzanyan, V.S. [Institute for Physical Research NAS, Ashtarak, 378410 (Armenia); Petrosyan, S.I. [Institute for Physical Research NAS, Ashtarak, 378410 (Armenia); Karapetyan, V.E. [Institute for Physical Research NAS, Ashtarak, 378410 (Armenia); Wood, K.S. [NRL, Washington, DC 20375 (United States); Wu, H.-D. [SFA/NRL, Washington, DC 20375 (United States); Gulian, A.M. [Physics Art Frontiers/NRL, Washington, DC 20375 (United States)

2006-09-15

263

Characterization of the Thermoelectric Behavior of Plastically Deformed Steels  

NASA Astrophysics Data System (ADS)

Different studies on the thermoelectric behavior of metals and metal alloys expose an influence of plastic deformation on the Seebeck coefficient. At present a detailed, quantitative analysis and descriptions of the effects of plastic deformation are not available, even though the thermoelectric properties are of fundamental importance for both theory and application. Therefore, the impact of plastic deformations on the temperature-dependent thermoelectric behavior of steel alloys is introduced in this paper. To achieve this, a device based on the integral measuring method was built to measure the relative Seebeck coefficient of steel alloys to platinum at different temperature gradients and for several degrees of plastic deformation. Well-defined values of plastic deformation were realized by cold rolling. With this compressive forming technology, logarithmic deformation up to 2.2 was set for all steel samples. Increasing plastic deformation results in a significant change in the relative Seebeck coefficient for all tested steel alloys. A relation between the thermoelectric behavior and plastic deformation of steels can be clearly illustrated based on the combination of metallurgical examinations and measurements of microhardness. These results provide new insights into the thermoelectric mechanism in steels in diverse plastic deformation states.

Demmel, P.; Pazureck, A.; Golle, R.; Volk, W.; Hoffmann, H.

2013-07-01

264

Effect of GaSb Addition on the Thermoelectric Properties of Mg2Si0.5Sn0.5 Solid Solutions  

NASA Astrophysics Data System (ADS)

Mg2Si0.5Sn0.5- xGaSb (0 ? x ? 0.15) solid solutions were synthesized by a B2O3 flux method followed by hot pressing. X-ray power diffraction analysis and scanning electron microscopy observations confirm that single-phase samples were obtained. The lattice constant monotonically increases with increasing GaSb content. It was found that the Seebeck coefficients showed weak temperature dependency after alloying with GaSb, being enhanced at high temperatures. The electrical conductivity increases while the lattice thermal conductivity decreases with increasing GaSb content. A maximum dimensionless figure of merit of 0.47 was obtained at 660 K for the sample with x = 0.08, mainly due to its high electrical conductivity.

Du, Z. L.; Jiang, G. Y.; Chen, Y.; Gao, H. L.; Zhu, T. J.; Zhao, X. B.

2012-06-01

265

AHSGE Cause and Effect  

NSDL National Science Digital Library

Cause and Effect practice to build skill knowledge for the reading portion of the graduation exam. Complete the Cause and Effect activities at your pace . Cause and Effect Match , Cause and Effect Mini Lesson and Game , What s the Cause?? Quiz . ...

Ufomadu, Ms.

2013-06-13

266

On Effect Size  

Microsoft Academic Search

The call for researchers to report and interpret effect sizes and their corresponding confidence intervals has never been stronger. However, there is confusion in the literature on the definition of effect size, and consequently the term is used inconsistently. We propose a definition for effect size, discuss 3 facets of effect size (dimension, measure\\/index, and value), outline 10 corollaries that

Ken Kelley; Kristopher J. Preacher

2012-01-01

267

On Effect Size  

ERIC Educational Resources Information Center

The call for researchers to report and interpret effect sizes and their corresponding confidence intervals has never been stronger. However, there is confusion in the literature on the definition of effect size, and consequently the term is used inconsistently. We propose a definition for effect size, discuss 3 facets of effect size (dimension,…

Kelley, Ken; Preacher, Kristopher J.

2012-01-01

268

Polymorphic effect systems  

Microsoft Academic Search

We present a new approach to programming languages for parallel computers that uses an effect system to discover expression scheduling constraints. This effect system is part of a 'kinded' type system with three base kinds: types, which describe the value that an expression may return; effects, which describe the side-effects that an expression may have; and regions, which describe the

John M. Lucassen; David K. Gifford

1988-01-01

269

A random effects model for effect sizes  

Microsoft Academic Search

Recent interest in quantitative research synthesis has led to the development of rigorous statistical theory for some of the methods used in meta-analysis. Statistical theory proposed previously has stressed the estimation of fixed but unknown population effect sizes (standardized mean differences). Theoretical considerations often suggest that treatment effects are not fixed but vary across different implementations of a treatment. The

Larry V. Hedges

1983-01-01

270

Effects of double filling of La and Ce on thermoelectric properties of Ce{sub m}La{sub n}Fe{sub 1.0}Co{sub 3.0}Sb{sub 12} compounds by spark plasma sintering  

SciTech Connect

Double-filled skutterudite compounds Ce{sub m}La{sub n}FeCo{sub 3}Sb{sub 12} with (m+n)=0.2-0.4 were synthesized by spark plasma sintering using powders of Co, Sb, Fe, and rare-earth Ce and La as starting materials, and the thermoelectric properties were studied in detail. The dominant phases of all the samples are the skutterudite with small amount of Sb as an impurity phase, and the amount of Sb decreases in double-filled compound. The lattice constant is enhanced linearly up to (m+n)=0.30 with increasing filling fraction and then unchanged. The Seebeck coefficient and thermal conductivity of double-filled compounds are generally higher than single-filled samples whatever the filling fraction is. Among all the samples, Ce{sub 0.1}La{sub 0.2}FeCo{sub 3}Sb{sub 12} shows the highest Seebeck coefficient of 150 {mu}V K{sup -1} at 773 K and the lowest thermal conductivity of 1.81 W/mK at 673 K, and the maximum ZT value reaches 0.60 at 773 K due to its lower thermal conductivity.

Lu, Q.M.; Zhang, J.X.; Zhang, X.; Liu, Y.Q.; Liu, D.M.; Zhou, M.L. [Key Laboratory of Advanced Functional Materials, Ministry of Education, College of Material Science and Engineering, Beijing University of Technology, Beijing 100022 (China)

2005-11-15

271

Kite Pseudo Effect Algebras  

NASA Astrophysics Data System (ADS)

We define a new class of pseudo effect algebras, called kite pseudo effect algebras, which is connected with partially ordered groups not necessarily with strong unit. In such a case, starting even with an Abelian po-group, we can obtain a noncommutative pseudo effect algebra. We show how such kite pseudo effect algebras are tied with different types of the Riesz Decomposition Properties. Kites are so-called perfect pseudo effect algebras, and we define conditions when kite pseudo effect algebras have the least non-trivial normal ideal.

Dvure?enskij, Anatolij

2013-11-01

272

Beyond First Stage Effects.  

National Technical Information Service (NTIS)

A first stage effect is something that creates greater efficiency. A Second stage effect impacts how people incorporate technologies into social systems. This incorporation causes changes in traditional organization and thought that result in true revolut...

J. L. Ledoux

2000-01-01

273

Modulational effects in accelerators.  

National Technical Information Service (NTIS)

We discuss effects of field modulations in accelerators, specifically those that can be used for operational beam diagnostics and beam halo control. In transverse beam dynamics, combined effects of nonlinear resonances and tune modulations influence diffu...

T. Satogata

1997-01-01

274

Side Effects (Management)  

MedlinePLUS

... cancer care is relieving side effects, called symptom management, palliative care, or supportive care. It is important ... treat them. To learn about the symptoms and management of the long-term side effects of cancer ...

275

Aeroelastic Thermal Effects.  

National Technical Information Service (NTIS)

The adverse effect of increasing temperature on the stability of turbomachinery airfoils was long recognized but remains today one that is not fully understood. The quantitative effect on the reduced frequency parameter, k = omega c/V, which was experimen...

J. D. Jeffers

1988-01-01

276

Effects of Aging  

MedlinePLUS

... and taking steps to counterbalance the effects of aging can help you maintain a young spirit and ... of many age-related changes. The Effects of Aging Aging Muscles: As muscles age, they begin to ...

277

Medications and Side Effects  

MedlinePLUS

... medication. WHEN & HOW SEVERE (1= NOT VERY/ SIDE EFFECT 5 = EXTREMELY)SUGGESTIONS FOR COPING Lack of energy/ ... doctor. WHEN & HOW SEVERE (1= NOT VERY/ SIDE EFFECT 5 = EXTREMELY)SUGGESTIONS FOR COPING Anxiety I Ask ...

278

Military Effectiveness: A Reappraisal.  

National Technical Information Service (NTIS)

Military effectiveness is a common goal among military forces, but it is an ill-defined concept. Two divergent theories cover the ground of military effectiveness. One looks at the interaction of social structures, whereas the other looks at the effect or...

J. J. Bernasconi

2007-01-01

279

Vectorial Photoelectric Effect  

Microsoft Academic Search

Experimental results and their analysis are presented which indicate that the vectorial photoelectric effect originates neither in excitation at the surface nor in pure volume optical absorption, but is a unique combined surface-volume effect which depends only on optical absorption as influenced by the interface. This effect can be phenomenologically regarded as surface-enhanced optical absorption (SEOA) in which, for certain

R. M. Broudy

1971-01-01

280

Allee effects in ants.  

PubMed

1. Allee effects occur when the aggregation of individuals result in mutually beneficial intraspecific interactions whereby individual fitness, or per capita growth rate, increases with the number of individuals. Allee effects are common in social species due to their cooperative behaviours, such as breeding, feeding or defence. Allee effects have important implications for many aspects of basic and applied ecology. Over the past decades, the study of Allee effects has influenced population dynamics, community ecology, endangered species management and invasion biology. 2. Despite the fact that cooperation is the basis of their social structure, Allee effects have received little attention among eusocial insects. Extreme cooperation is common, and reproductive specialization of individuals occurs due to division of labour. These life-history traits suggest that the potential contribution of each caste to reproduction and survival may be differential and nonadditive. 3. We studied Allee effects in the invasive Argentine ant (Linepithema humile). In this species, many queens and workers are present in colonies, which allowed us to explore the differential effects of castes on the presence of Allee effects. In the laboratory, we measured brood production and individual survival in experimental colonies that differed in the initial numbers of queens and workers.4. Our results highlight the differential effect of queens and workers on survival and productivity. We found three positive density-dependent relationships indicative of component Allee effects at the colony level: both workers and queens had a positive effect on the productivity of the other caste, and queens had a positive effect on worker survivorship. 5. Our experimental results suggest a potential positive feedback between worker and queen abundance, which may have contributed to the evolution of large colony sizes. Our study provides the first evidence of Allee effects in eusocial insects and highlights the need to consider castes separately in population dynamics. Division of labour and differential reproductive rates are factors that should be integrated into the study of Allee effects. PMID:23672650

Luque, Gloria M; Giraud, Tatiana; Courchamp, Franck

2013-09-01

281

Giant thermoelectric effect in graphene-based topological insulators with heavy adatoms and nanopores.  

PubMed

Designing thermoelectric materials with high figure of merit ZT = S(2)GT/Ktot requires fulfilling three often irreconcilable conditions, that is, the high electrical conductance G, small thermal conductance Ktot, and high Seebeck coefficient S. Nanostructuring is one of the promising ways to achieve this goal as it can substantially suppress lattice contribution to Ktot. However, it may also unfavorably influence the electronic transport in an uncontrollable way. Here, we theoretically demonstrate that this issue can be ideally solved by fabricating graphene nanoribbons with heavy adatoms and nanopores. The adatoms locally enhance spin-orbit coupling in graphene thereby converting it into a two-dimensional topological insulator with a band gap in the bulk and robust helical edge states, which carry electrical current and generate a highly optimized power factor S(2)G per helical conducting channel due to narrow boxcar-function-shaped electronic transmission (surpassing even the Mahan-Sofo limit obtained for delta-function-shaped electronic transmission). Concurrently, the array of nanopores impedes the lattice thermal conduction through the bulk. Using quantum transport simulations coupled with first-principles electronic and phononic band structure calculations, the thermoelectric figure of merit is found to reach its maximum ZT ? 3 at low temperatures T ? 40 K. This paves a way to design high-ZT materials by exploiting the nontrivial topology of electronic states through nanostructuring. PMID:24932511

Chang, Po-Hao; Bahramy, Mohammad Saeed; Nagaosa, Naoto; Nikoli?, Branislav K

2014-07-01

282

Effect of assisted hopping on thermopower in an interacting quantum dot  

NASA Astrophysics Data System (ADS)

We investigate the electrical conductance and thermopower of a quantum dot tunnel coupled to external leads described by an extension of the Anderson impurity model which takes into account the assisted hopping processes, i.e., the occupancy-dependence of the tunneling amplitudes. We provide analytical understanding based on scaling arguments and the Schrieffer-Wolff transformation, corroborated by detailed numerical calculations using the numerical renormalization group method. The assisted hopping modifies the coupling to the two-particle state, which shifts the Kondo exchange coupling constant and exponentially reduces or enhances the Kondo temperature, breaks the particle-hole symmetry, and strongly affects the thermopower. We discuss the gate-voltage and temperature dependence of the transport properties in various regimes. For a particular value of the assisted hopping parameter we find peculiar discontinuous behaviour in the mixed-valence regime. Near this value, we find very high Seebeck coefficient. We show that, quite generally, the thermopower is a highly sensitive probe of assisted hopping and Kondo correlations.

Tooski, S. B.; Ramšak, A.; Bu?ka, B. R.; Žitko, R.

2014-05-01

283

Effects of Cu5Zn3 addition on the thermoelectric properties of Zn4Sb3  

NASA Astrophysics Data System (ADS)

The structures and thermoelectric properties of mCu5Zn3.nZn4Sb3 with multiphase coexistence are reported. Rietveld analysis reveals that at least 92.3% wt % ?-Zn4Sb3 phase can be obtained with only small quantities of ZnSb and Cu5Zn8 phases precipitated after proper Cu5Zn3 addition. Measurements indicate that although the ?-Zn4Sb3 phase plays a determining role in controlling the transport properties involving the Seebeck coefficient, electrical conductivity, and thermal conductivity, the impurity phases Cu5Zn8 and ZnSb with a crooked riverlike and intertwined tree stump morphologies, respectively, are still of great significance to tune the thermoelectric performance. The highest ZT value of 0.84 can be obtained for the alloy mCu5Zn3.nZn4Sb3 (m/n=1/200) at 631 K, approximately 1.8 times that of undoped ?-Zn4Sb3, proving that a good combination between the transports of carriers and phonons can be achieved if a proper dopant is introduced in the Zn4Sb3 matrix.

Cui, J. L.; Fu, H.; Mao, L. D.; Chen, D. Y.; Liu, X. L.

2009-07-01

284

How effective are maternal effects at having effects?  

PubMed Central

The well studied trade-off between offspring size and offspring number assumes that offspring fitness increases with increasing per-offspring investment. Where mothers differ genetically or exhibit plastic variation in reproductive effort, there can be variation in per capita investment in offspring, and via this trade-off, variation in fecundity. Variation in per capita investment will affect juvenile performance directly—a classical maternal effect—while variation in fecundity will also affect offspring performance by altering the offsprings' competitive environment. The importance of this trade-off, while a focus of evolutionary research, is not often considered in discussions about population dynamics. Here, we use a factorial experiment to determine what proportion of variation in offspring performance can be ascribed to maternal effects and what proportion to the competitive environment linked to the size–number trade-off. Our results suggest that classical maternal effects are significant, but that in our system, the competitive environment, which is linked to maternal environments by fecundity, can be a far more substantial influence.

Beckerman, Andrew P; Benton, Tim G; Lapsley, Craig T; Koesters, Nils

2005-01-01

285

The butterfly effect of the "butterfly effect".  

PubMed

The "Butterfly Effect" metaphor states with variance that the flap of a butterfly's wings in Brazil can cause a tornado in Texas. This metaphor has become part of the common vernacular of Western culture. In this paper I discuss the origins of the metaphor, examine its current usage within popular culture, and present an argument as to why it is popular. I propose that the metaphor is a type of semantic attractor, a narrative device with invariant meaning but audience-specific contextualization. Finally I address whether the Butterfly Effect metaphor is a good example of itself. PMID:19527619

Dooley, Kevin J

2009-07-01

286

Thermally Driven Josephson Effect  

NASA Technical Reports Server (NTRS)

A concept is proposed of the thermally driven Josephson effect in superfluid helium. Heretofore, the Josephson effect in a superfluid has been recognized as an oscillatory flow that arises in response to a steady pressure difference between two superfluid reservoirs separated by an array of submicron-sized orifices, which act in unison as a single Josephson junction. Analogously, the thermally driven Josephson effect is an oscillatory flow that arises in response to a steady temperature difference. The thermally driven Josephson effect is partly a consequence of a quantum- mechanical effect known as the fountain effect, in which a temperature difference in a superfluid is accompanied by a pressure difference. The thermally driven Josephson effect may have significance for the development of a high-resolution gyroscope based on the Josephson effect in a superfluid: If the pressure-driven Josephson effect were used, then the fluid on the high-pressure side would become depleted, necessitating periodic interruption of operation to reverse the pressure difference. If the thermally driven Josephson effect were used, there would be no net flow and so the oscillatory flow could be maintained indefinitely by maintaining the required slightly different temperatures on both sides of the junction.

Penanen, Konstantin; Chui, Talso

2008-01-01

287

The Hubble effective potential  

SciTech Connect

We generalize the effective potential to scalar field configurations which are proportional to the Hubble parameter of a homogeneous and isotropic background geometry. This may be useful in situations for which curvature effects are significant. We evaluate the one loop contribution to the Hubble Effective Potential for a massless scalar with arbitrary conformal and quartic couplings, on a background for which the deceleration parameter is constant. Among other things, we find that inflationary particle production leads to symmetry restoration at late times.

Janssen, T.M.; Miao, S.P.; Prokopec, T. [Institute for Theoretical Physics and Spinoza Institute, Utrecht University, Leuvenlaan 4, Postbus 80.195, 3508 TD Utrecht (Netherlands)] [Institute for Theoretical Physics and Spinoza Institute, Utrecht University, Leuvenlaan 4, Postbus 80.195, 3508 TD Utrecht (Netherlands); Woodard, R.P., E-mail: T.M.Janssen@uu.nl, E-mail: S.Miao@uu.nl, E-mail: T.Prokopec@uu.nl, E-mail: woodard@phys.ufl.edu [Department of Physics, University of Florida, Gainesville, FL 32611 (United States)

2009-05-15

288

Dynamic ground effects  

NASA Technical Reports Server (NTRS)

A research program is underway at the NASA Langley Research Center to study the effect of rate of descent on ground effects. A series of powered models were tested in the Vortex Research Facility under conditions with rate of descent and in the 14 x 22 Foot Subsonic Tunnel under identical conditions but without rate of descent. These results indicate that the rate of descent can have a significant impact on ground effects particularly if vectored or reversed thrust is used.

Paulson, John W., Jr.; Kemmerly, Guy T.; Gilbert, William P.

1990-01-01

289

Electronic thermal transport in strongly correlated multilayered nanostructures  

NASA Astrophysics Data System (ADS)

The formalism for a linear-response many-body treatment of the electronic contributions to thermal transport is developed for multilayered nanostructures. By properly determining the local heat-current operator, it is possible to show that the Jonson-Mahan theorem for the bulk can be extended to inhomogeneous problems, so the various thermal-transport coefficient integrands are related by powers of frequency (including all effects of vertex corrections when appropriate). We illustrate how to use this formalism by showing how it applies to measurements of the Peltier effect, the Seebeck effect, and the thermal conductance.

Freericks, J. K.; Zlati?, V.; Shvaika, A. M.

2007-01-01

290

Volcanic effects on climate  

NASA Technical Reports Server (NTRS)

Volcanic eruptions which inject large amounts of sulfur-rich gas into the stratosphere produce dust veils which last years and cool the earth's surface. At the same time, these dust veils absorb enough solar radiation to warm the stratosphere. Since these temperature changes at the earth's surface and in the stratosphere are both in the opposite direction of hypothesized effects from greenhouse gases, they act to delay and mask the detection of greenhouse effects on the climate system. Tantalizing recent research results have suggested regional effects of volcanic eruptions, including effects on El Nino/Southern Oscillation (ENSO). In addition, a large portion of the global climate change of the past 100 years may be due to the effects of volcanoes, but a definite answer is not yet clear. While effects of several years were demonstrated with both data studies and numerical models, long-term effects, while found in climate model calculations, await confirmation with more realistic models. Extremely large explosive prehistoric eruptions may have produced severe weather and climate effects, sometimes called a 'volcanic winter'. Complete understanding of the above effects of volcanoes is hampered by inadequacies of data sets on volcanic dust veils and on climate change. Space observations can play an increasingly important role in an observing program in the future. The effects of volcanoes are not adequately separated from ENSO events, and climate modeling of the effects of volcanoes is in its infancy. Specific suggestions are made for future work to improve the knowledge of this important component of the climate system.

Robock, Alan

1991-01-01

291

Handbook of radiation effects  

Microsoft Academic Search

This book emphasizes radiation effects on solid state devices from exposure to the types of radiation found outside the atmosphere (in space, or in the vicinity of an exploding nuclear device). It contains a basic study of radiation shielding of payload components for payloads in space and specifically covers radiation effects on minority and majority carriers, optical media and organic

A. Holmes-Siedle; L. Adams

1993-01-01

292

Evaluating Effective Management Learning.  

ERIC Educational Resources Information Center

A better way to assess the effectiveness of management development is to measure organizational effectiveness rather than individual improvement. Case studies support the Business Excellence Framework model, which assesses enablers (leadership, personnel management, policy, resources, processes) and results (personnel and customer satisfaction,…

Bramley, Peter

1999-01-01

293

[Providing Effective Behavior Support.  

ERIC Educational Resources Information Center

This theme issue addresses the provision of behavioral support for students with behavior disorders. The first article, "Providing Effective Behavior Support to All Students: Procedures and Processes" (George Sugai), summarizes the literature on the effectiveness of various interventions and offers several models for examining the teaching of…

SAIL: Technical Assistance Journal, 1996

1996-01-01

294

Named Rules and Effects  

NSDL National Science Digital Library

Hans Reich, professor of organic chemistry at the University of Wisconsin Madison, created this online handout on named rules and effects in organic chemistry. Concise descriptions and structures of a number of named effects, rules, stereochemical models and hypothesesâÂÂfrom BaldwinâÂÂs rules to the ZimmermanâÂÂTraxler transition stateâÂÂare given.

Reich, Hans J.

2007-12-21

295

Institutional Effectiveness Report.  

ERIC Educational Resources Information Center

This is the first edition of the College of the Canyon's (California) Institutional Effectiveness Report, which is modeled after the statewide report prepared by the Chancellor's Office. The college is measuring 60 effectiveness indicators in four mission areas: student access, student success, staff composition, and fiscal condition. A brief…

College of the Canyons, Santa Clarita, CA.

296

Comparative Effectiveness Research  

Cancer.gov

Comparative Effectiveness Research (CER) is the conduct and synthesis of systematic research comparing different interventions and strategies to prevent, diagnose, treat and monitor health conditions. The purpose of this research is to inform patients, providers, and decision-makers about which interventions are most effective for which patients under specific circumstances.

297

Earthquake Effects and Experiences  

NSDL National Science Digital Library

This portion of the United States Geological Survey's (USGS) frequently-asked-questions feature on earthquakes addresses what individuals might actually experience during an earthquake. Topics include earthquake motion (rolling or shaking), earthquake effects (ground shaking, surface faulting, ground failure, etc.), earthquake magnitude, what an earthquake feels like, and others. There are also links to additional resources on earthquake effects and experiences.

2010-11-23

298

Effects of Drug Abuse  

MedlinePLUS

Listen to this page Effects of Drug Abuse Drug abuse hurts the people who take drugs AND the people around them, including families , kids , and ... HIV/AIDS Click here to learn more about effects of specific drugs . VIDEO: Why Are Drugs So ...

299

Effects of acid precipitation  

Microsoft Academic Search

A growing body of evidence suggests that acid rain is responsible for substantial adverse effects on the public welfare. Such effects include: the acidification of lakes and rivers, with resultant damage to fish and other components of aquatic ecosystems; acidification and demineralization of soils; and possible reductions in crop and forest productivity. Affected areas include Canada and the northeastern US.

Norman R. Glass; Gary E. Glass; Peter J. Rennie

1979-01-01

300

Hall Effect in Ferromagnetics  

Microsoft Academic Search

Both the unusually large magnitude and strong temperature dependence of the extraordinary Hall effect in ferromagnetic materials can be understood as effects of the spin-orbit interaction of polarized conduction electrons. It is shown that the interband matrix elements of the applied electric potential energy combine with the spin-orbit perturbation to give a current perpendicular to both the field and the

Robert Karplus; J. M. Luttinger

1954-01-01

301

Quantum zeno effect  

Microsoft Academic Search

Misra and Sudarshan pointed out, based on the quantum measurement theory, that repeated measurements lead to a slowing down of the transition, which they called the quantum Zeno effect. Recently, Itano, Heinzen, Bollinger and Wineland have reported that they succeeded in observing that effect. We show that the results of Itano et al. can be recovered through conventional quantum mechanics

T. Petrosky; S. Tasaki; I. Prigogine

1990-01-01

302

A ''Voice Inversion Effect?''  

ERIC Educational Resources Information Center

Voice is the carrier of speech but is also an ''auditory face'' rich in information on the speaker's identity and affective state. Three experiments explored the possibility of a ''voice inversion effect,'' by analogy to the classical ''face inversion effect,'' which could support the hypothesis of a voice-specific module. Experiment 1 consisted…

Bedard, Catherine; Belin, Pascal

2004-01-01

303

The greenhouse effect  

Microsoft Academic Search

The greenhouse effect on the Earth is identified by the difference between the effective radiating temperature of the planet and its surface temperature. The difference between the energy emitted by the surface and that emitted upward to space by the upper atmosphere quantifies it; it can therefore be defined as the long wave energy trapped in the atmosphere. Climate forcing

A. Berger; Ch. Tricot

1992-01-01

304

The Greenhouse Effect  

Microsoft Academic Search

The Greenhouse Effect is getting a lot of publicity as concern grows about trends in weather and pollution. The midwestern states of the US suffered a drought during 1988 coupled with an unsually hot summer throughout the country. Many people attributed this to the Greenhouse Effect. Palmer and Brankovic (Nature, Vol. 338, page 54, March 2, 1989) tied the drought

2009-01-01

305

Effects on aquatic ecosystems  

Microsoft Academic Search

Regarding the effects of UV-B radiation on aquatic ecosystems, recent scientific and public interest has focused on marine primary producers and on the aquatic web, which has resulted in a multitude of studies indicating mostly detrimental effects of UV-B radiation on aquatic organisms. The interest has expanded to include ecologically significant groups and major biomass producers using mesocosm studies, emphasizing

D.-P. Häder; H. D. Kumar; R. C. Smith; R. C. Worrest

1998-01-01

306

Lake Effect Snow  

NSDL National Science Digital Library

This MPEG shows lake effect precipitation resulting when cold air masses pass over the relatively warm Great Lakes, pick up moisture, and then precipitate when again encountering the cold land surface. Note the bands of lake effect snow apparent over Lake Superior and the lack of snow on the western shore of Lake Michigan. The animation can be replayed to stress important points.

Nasa

307

The Chelate Effect Redefined.  

ERIC Educational Resources Information Center

Discusses ambiguities of the accepted definition of the chelate effect, suggesting that it be defined in terms of experimental observation rather than mathematical abstraction. Indicates that the effect depends on free energy change in reaction, ligand basicity, pH of medium, type of chelates formed, and concentration of ligands in solution. (JN)

da Silva, J. J. R. Frausto

1983-01-01

308

JPL Radiation Effects Facilities  

NASA Technical Reports Server (NTRS)

Radiation Effects Group investigates the effects of space radiation on present and future microelectronic and optoelectronic technologies, evaluate the risk of using them in specific space missions, and recommend component and design techniques for JPL and NASA programs to reduce reliability risk from space radiation.

Thorbourn, Dennis

2013-01-01

309

The greenhouse effect  

NASA Astrophysics Data System (ADS)

The greenhouse effect on the Earth is identified by the difference between the effective radiating temperature of the planet and its surface temperature. The difference between the energy emitted by the surface and that emitted upward to space by the upper atmosphere quantifies it; it can therefore be defined as the long wave energy trapped in the atmosphere. Climate forcing and the response of the climate system within which climate feedback mechanisms are contained, will be defined in this review. Quantitative examples will illustrate what could happen if the greenhouse effect is perturbed by the human activities, in particular if atmospheric CO2 concentrations would double in the future. Recent measurements by satellites of the greenhouse effect will be given. The net cooling effect of clouds on the Earth and whether or not there will be less cooling by clouds as the planet warms, are discussed following a series of papers recently published by Ramanathan and his collaborators.

Berger, A.; Tricot, Ch.

1992-11-01

310

Effective Frequency Technique  

NASA Technical Reports Server (NTRS)

An effective monochromatic frequency technique is described to represent the effects of finite spectral bandwidth for active and passive measurements centered on an absorption line, a trough region, or a slowly varying spectral feature. For Gaussian and rectangular laser line shapes, the effective frequency is shown to have a simple form which depends only on the instrumental line shape and bandwidth and not on the absorption line profile. The technique yields accuracies better than 0.1% for bandwidths less than 0.2 times the atmospheric line width.

Kirk, C. Laurence; Weng, Chi Y.

2002-01-01

311

Improving engineering effectiveness  

NASA Technical Reports Server (NTRS)

Methodologies to improve engineering productivity were investigated. The rocky road to improving engineering effectiveness is reviewed utilizing a specific semiconductor engineering organization as a case study. The organization had a performance problem regarding new product introductions. With the help of this consultant as a change agent the engineering team used a systems approach to through variables that were effecting their output significantly. Critical factors for improving this engineering organization's effectiveness and the roles/responsibilities of management, the individual engineers and the internal consultant are discussed.

Fiero, J. D.

1985-01-01

312

[Cholinergic effects of nootropics].  

PubMed

With respect to the enhancing effect of nootropics on learning and memory, the influence of some of these drugs on the high affinity choline uptake has been investigated. Meclofenoxate competes with choline uptake in vitro because of its similar side chain; other nootropics are without in vitro effects. A single dose of pramiracetam enhances the choline uptake in cortex and hippocampus. Application of meclofenoxate decreases the uptake of choline. Other nootropics lack acute effects. Possible increases of uptake after repeated dosage disappear within 24 h. PMID:3149192

Funk, K F; Schmidt, J

1988-01-01

313

From effective interactions to effective operators  

NASA Astrophysics Data System (ADS)

One of the most successful approaches to the nuclear structure of light nuclei is the no-core shell model (NCSM), which describes with very good precision the observed nuclear spectra. In its framework, by means of the Lee Suzuki procedure one derives effective interactions in finite model spaces starting from realistic nucleon-nucleon (NN) potentials; the low-lying energy spectrum is then obtain through the diagonalization of the ab initio effective interactions in large, translationally invariant, many-body basis. In addition to energy levels, one has to obtain good description of the nuclear wave functions; the latter can be tested by computing observables and transition strengths. With a few exceptions, transition strengths and expectation values of observables have been obtained using bare operators restricted to the model space. We have started recently to apply the Lee-Suzuki procedure to general operators and performed tests in restricted model spaces. In this work, we compute expectation values of selected scalar observables and electromagnetic transition strengths using realistic wave functions for nuclei in the p shell. I.S. and B.R.B acknowledge partial support by NFS grants PHY0070858 and PHY0244389. The work was performed in part under the auspices of the U. S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48. P.N. received support from LDRD contract 04-ERD-058.

Stetcu, Ionel; Barrett, Bruce R.; Navratil, Petr

2004-10-01

314

Authoring Effective Demonstrations.  

National Technical Information Service (NTIS)

The changing tactics of asymmetric threats present an ongoing need to disseminate lessons learned from the battlefield to a wide audience of personnel. Interactive virtual environments have been shown to be effective for team training, and distributed gam...

D. Fu E. Salas M. A. Rosen R. Jensen S. Ramachandran

2007-01-01

315

Explore Learning: Doppler Effect  

NSDL National Science Digital Library

This site contains a Shockwave interactive animation used to teach students about the wave motion specific to doppler effect. Users can change frequency, wave speed, as well as source and detector speeds.

2004-12-15

316

Vaccine herd effect  

PubMed Central

Vaccination ideally protects susceptible populations at high risk for complications of the infection. However, vaccines for these subgroups do not always provide sufficient effectiveness. The herd effect or herd immunity is an attractive way to extend vaccine benefits beyond the directly targeted population. It refers to the indirect protection of unvaccinated persons, whereby an increase in the prevalence of immunity by the vaccine prevents circulation of infectious agents in susceptible populations. The herd effect has had a major impact in the eradication of smallpox, has reduced transmission of pertussis, and protects against influenza and pneumococcal disease. A high uptake of vaccines is generally needed for success. In this paper we aim to provide an update review on the herd effect, focusing on the clinical benefit, by reviewing data for specific vaccines.

Kim, Tae Hyong; Johnstone, Jennie; Loeb, Mark

2011-01-01

317

UCAR: The Greenhouse Effect  

NSDL National Science Digital Library

This site by the University Corporation for Atmospheric Research (UCAR) provides an overview of the earth's atmospheric "greenhouse effect." Diagrams and one short video help present the key ideas. Two related activities are also provided.

2006-12-03

318

Aviation Noise Effects.  

National Technical Information Service (NTIS)

This report summarizes the effects of aviation noise in many areas, ranging from human annoyance to impact on real estate values. It also synthesizes the findings of literature on several topics. Included in the literature were many original studies carri...

J. S. Newman K. R. Beattie

1985-01-01

319

The Gravitational Edge Effect.  

National Technical Information Service (NTIS)

The knowledge that a gravity anomaly is due to an edge effect is sufficient to resolve the inherent ambiguity of the inverse potential problem. Thus given the gravity field across the contact between two laterally uniform structures, the density differenc...

L. M. Dorman

1974-01-01

320

[Genetic effects of radiation].  

PubMed

This paper is a short review of genetic effect of radiation. This includes methods and results of a large-scale genetic study on specific loci in mice and of various studies in the offspring of atomic-bomb survivors. As for the latter, there is no results obtained which suggest the effect of parental exposure to radiation. Further, in recent years, studies are conducted to the offspring born to parents who were survivors of childhood cancers. In several reports, the mean gonad dose is quite large whereas in most instances, the results do not indicate genetic effect following parental exposure to radiation. Possible reasons for the difficulties in detecting genetic effect of radiation are discussed. PMID:22514926

Nakamura, Nori

2012-03-01

321

Human Health Effects Assays.  

National Technical Information Service (NTIS)

The use of assays to evaluate and assist in predicting potentially adverse human health effects associated with exposure to pollutants in water (that is, municipal wastewater, sewage sludge, ambient water, and drinking water) is the focus of the review.

L. Fradkin C. Sonich-Mullin M. Cerny C. Kruger F. Cavender

1989-01-01

322

Radiation effects in space  

SciTech Connect

The paper discusses the radiation environment in space that astronauts are likely to be exposed to. Emphasis is on proton and HZE particle effects. Recommendations for radiation protection guidelines are presented. (ACR)

Fry, R.J.M.

1986-01-01

323

Substituent Effect in Ketoferrocenes.  

National Technical Information Service (NTIS)

The effect of carbonyl-group on the redox potential and Moessbauer parameters was studied in ketoferrocenes and chalcone analogous ferrocene derivatives. Interaction of electron-donating and electron-withdrawing substituents and the carbonyl-group is disc...

A. G. Nagy

1983-01-01

324

Metabolic Effects of Monomethylhydrazine.  

National Technical Information Service (NTIS)

The metabolic effects of monomethylhydrazine (MMH) were studied in rats using whole body calorimetry and measurements of serum and liver levels of fat and carbohydrate. Biochemical measurements were made in rats sacrificed three hours after injection of n...

H. L. Bitter D. A. Clark W. W. Lackey

1967-01-01

325

Managing for Effective Teaching.  

ERIC Educational Resources Information Center

In 20 schools, surveys of teacher perceptions about management styles and student perceptions of teachers reveals a correlation between effective teaching and "consultative-centralized" management. Consequently, 10 "commandments" for good consultative management are provided. (TE)

Greenblatt, Ruth B.; And Others

1984-01-01

326

Coefficients of Effective Length.  

ERIC Educational Resources Information Center

Under certain conditions, a validity Coefficient of Effective Length (CEL) can produce highly misleading results. A modified coefficent is suggested for use when empirical studies indicate that underlying assumptions have been violated. (Author/BW)

Edwards, Roger H.

1981-01-01

327

Indicators of Administrative Effectiveness.  

ERIC Educational Resources Information Center

Ten personal characteristics and seven administrative skills that differentiated effective from ineffective university leaders were assessed by multiple discriminate analysis. The personal characteristics identified by previous research (Skipper, 1975, 1977) are: responsibility, integrity, self-control, intellectual efficiency, flexibility,…

Skipper, Charles E.; Hofmann, Richard J.

328

Brookhaven Radiation Effects Facility.  

National Technical Information Service (NTIS)

The Neutral Particle Beam (NPB) Radiation Effects Facility (REF), funded by the Strategic Defense Initiative Office (SDIO) through the Defense Nuclear Agency (DNA) and the Air Force Weapons Laboratory (AFWL), has been constructed at Brookhaven National La...

C. L. Snead P. Grand T. Ward

1988-01-01

329

PPP Effectiveness Study.  

National Technical Information Service (NTIS)

This design note presents a study of the Procedures and Performance Program (PPP) effectiveness. The intent of the study is to determine manpower time savings and the improvements in job performance gained through PPP automated techniques. The discussion ...

J. D. Arbet R. L. Benbow

1976-01-01

330

Physiological Effects of Training.  

National Technical Information Service (NTIS)

With the evolution of exercise science a vast amount of information concerning the physiological effects of training has been generated. Understanding the basic training responses and adaptations of various modes of conditioning can give the clinician ins...

W. J. Kraemer W. L. Daniels

1985-01-01

331

Health Effects of Tsunamis  

MedlinePLUS

... for Pet Owners Frequently Asked Questions Additional Information Tornadoes Preparing for a Tornado (Part 1 of 2) ... Severe Weather Earthquakes Extreme Heat Floods Hurricanes Landslides Tornadoes Tsunamis Volcanoes Wildfires Winter Weather Health Effects of ...

332

Effectiveness of Glare Screens.  

National Technical Information Service (NTIS)

Available literature on glare screens was reviewed and selected installations were inspected. It was found that glare screens are effective but that warrants have not been established for their use. Expanded metal meshes are the most satisfactory of the a...

J. T. Capelli

1973-01-01

333

UNDERGROUND EXPLOSION EFFECTS  

Microsoft Academic Search

Measurements were made of surface and subsurface effects of an ; underground explosion of a 1.2-kt nuclear burst. The measurements included free-; field earth and air-blast effects, as well as loading on underground structural ; devices. From the 76 channels installed on TEAPOT Shot 7, 75 usable records were ; obtained. The free-field quantities measured include air-blast pressure, earth ;

D. C. Sachs; L. M. Swift

1958-01-01

334

Nocturnal aircraft noise effects.  

PubMed

Noise protection associated with the construction and extension of airports in the Federal Republic of Germany has been regulated by the law for protection against aircraft noise since 1971. This legislation is due for revision because of different aspects. One aspect is the growth of air traffic which has led many airports to the limits of their capacity and in search of new ways of adaptation to the increasing demand for flight services. Another aspect is the increasing concern of the population about noise effects which has to be addressed by better protection against the effects of aircraft noise. The framework conditions of policy in terms of society as a whole, its health and economic environment need to be put into effect by political action. Science can contribute to this goal by performing noise effects research and by providing recommendations to the political body. However, it remains controversial, what measures are necessary or adequate to assure effective protection of the population against aircraft noise. This is particularly true for the protection of rest and sleep at night. The problem of finding a common basis for adequate recommendations is associated with (1) the low number of primary studies, which also exhibited highly variable results and assessments, (2) the handling of acoustic or psycho-acoustic dimensions for quantifying psychological or physiological reactions, and (3) the conception of how far preventive measures have to go to prove effective. With this in mind, the DLR Institute for Aerospace Medicine is conducting a large-scale, multi-stage study for investigating the acute effects of nocturnal aircraft noise on human sleep. This enterprise is implemented in the framework of the HGF/DLR project "Quiet Air Traffic" for developing sustainable assessment criteria for human-specific effects of aircraft noise at night. PMID:15070533

Basner, M; Samel, A

2004-01-01

335

Acid Rain Effects  

NSDL National Science Digital Library

Learners conduct a simple experiment to model and explore the harmful effects of acid rain (vinegar) on living (green leaf and eggshell) and non-living (paper clip) objects. Learners observe the effects over a period of days. This activity has links to other activities which can be combined to make a larger lesson. Resource contains vocabulary definitions and suggestions for assessment, extensions, and scaling for different levels of learners.

Kolenbrander, Amy; Yowell, Janet; Mach, Natalie; Zarske, Malinda S.; Carlson, Denise

2004-01-01

336

The Doppler Effect  

NSDL National Science Digital Library

This Flash animation provides a simulation of the Doppler effect. The user can change the speed of the wave source and can move a microphone to detect the wave frequency at different points relative to the moving source. The resulting wave pattern can be both observed and heard. Instructional notes outlining the details of the Doppler effect are provided. This material is part of a web site for a second semester physics course for majors covering gravity, fluids, waves, and thermodynamics.

Fowler, Michael; Welch, Heather

2008-07-31

337

Pleiotropic effects of pitavastatin  

PubMed Central

3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) are established first line treatments for hypercholesterolaemia. In addition to the direct effects of statins in reducing concentrations of atherogenic low density lipoprotein cholesterol (LDL-C), several studies have indicated that the beneficial effects of statins may be due to some of their cholesterol-independent, multiple (pleiotropic) effects which may differ between different members of the class. Pitavastatin is a novel synthetic lipophilic statin that has a number of pharmacodynamic and pharmacokinetic properties distinct from those of other statins, which may underlie its potential pleiotropic benefits in reducing cardiovascular risk factors. This review examines the principal pleiotropic effects of pitavastatin on endothelial function, vascular inflammation, oxidative stress and thrombosis. The article is based on a systematic literature search carried out in December 2010, together with more recent relevant publications where appropriate. The available data from clinical trials and in vitro and animal studies suggest that pitavastatin is not only effective in reducing LDL-C and triglycerides, but also has a range of other effects. These include increasing high density lipoprotein cholesterol, decreasing markers of platelet activation, improving cardiac, renal and endothelial function, and reducing endothelial stress, lipoprotein oxidation and, ultimately, improving the signs and symptoms of atherosclerosis. It is concluded that the diverse pleiotropic actions of pitavastatin may contribute to reducing cardiovascular morbidity and mortality beyond that achieved through LDL-C reduction.

Davignon, Jean

2012-01-01

338

High Burnup Effects Program  

SciTech Connect

This is the final report of the High Burnup Effects Program (HBEP). It has been prepared to present a summary, with conclusions, of the HBEP. The HBEP was an international, group-sponsored research program managed by Battelle, Pacific Northwest Laboratories (BNW). The principal objective of the HBEP was to obtain well-characterized data related to fission gas release (FGR) for light water reactor (LWR) fuel irradiated to high burnup levels. The HBEP was organized into three tasks as follows: Task 1 -- high burnup effects evaluations; Task 2 -- fission gas sampling; and Task 3 -- parameter effects study. During the course of the HBEP, a program that extended over 10 years, 82 fuel rods from a variety of sources were characterized, irradiated, and then examined in detail after irradiation. The study of fission gas release at high burnup levels was the principal objective of the program and it may be concluded that no significant enhancement of fission gas release at high burnup levels was observed for the examined rods. The rim effect, an as yet unquantified contributor to athermal fission gas release, was concluded to be the one truly high-burnup effect. Though burnup enhancement of fission gas release was observed to be low, a full understanding of the rim region and rim effect has not yet emerged and this may be a potential area of further research. 25 refs., 23 figs., 4 tabs.

Barner, J.O.; Cunningham, M.E.; Freshley, M.D.; Lanning, D.D.

1990-04-01

339

Thermally driven spin and charge currents in thin NiFe2O4/Pt films  

NASA Astrophysics Data System (ADS)

We present results on the longitudinal spin Seebeck effect (LSSE) shown by semiconducting ferrimagnetic NiFe2O4/Pt films from room temperature down to 50 K base temperature. The temperature dependence of the conductivity has been studied in parallel to obtain information about the origin of the electric potentials detected at the Pt coverage of the ferrimagnet in order to distinguish the LSSE from the anomalous Nernst effect. Furthermore, the dependence of the LSSE on temperature gradients as well as the influence of an external magnetic field direction is investigated.

Meier, D.; Kuschel, T.; Shen, L.; Gupta, A.; Kikkawa, T.; Uchida, K.; Saitoh, E.; Schmalhorst, J.-M.; Reiss, G.

2013-02-01

340

Thermomagnetic phenomena in the mixed state of high temperature superconductors  

NASA Technical Reports Server (NTRS)

Galvano- and thermomagnetic-phenomena in high temperature superconductors, based on kinetic coefficients, are discussed, along with a connection between the electric field and the heat flow in superconductor mixed state. The relationship that determines the transport coefficients of high temperature superconductors in the mixed state based on Seebeck and Nernst effects is developed. It is shown that this relationship is true for a whole transition region of the resistive mixed state of a superconductor. Peltier, Ettingshausen and Righi-Leduc effects associated with heat conductivity as related to high temperature superconductors are also addressed.

Meilikhov, E. Z.

1995-01-01

341

Effective Transport Properties  

NASA Astrophysics Data System (ADS)

In this chapter we study a particular case of multiphase systems, namely two-phase materials in which one of the phases is randomly dispersed in the other, so that the composite can be viewed on a macroscale as an effective continuum, with well defined properties. In general, the theoretical determination of the parameter for an effective medium requires, as a rule, the solution of a corresponding transport problem at the microscale, which takes into account the morphology of the system and its evolution. As the mathematical problem is well-posed on a microscale, this can be accomplished using, for example, the multiple scale approach shown in Chap. 11 ; however, the task requires massive computations and is therefore difficult to implement from the practical standpoint. Here, instead, we focus on a deterministic approach to the problem, where the geometry and spatial configuration of the particles comprising the included phase are given and the solution to the microscale problem is therefore sought analytically. As examples, we study the effective thermal conductivity of solid reinforced materials (Sect. 10.1), the effective viscosity of non-colloidal suspensions (Sect. 10.2), the effective permeability of porous materials (10.3) and the effective self- and gradient diffusivities of colloidal suspensions (Sect. 10.4). Then, in Sect. 10.5, an alternative dynamic definition of the transport coefficients is considered, which can also serve as a basis to determine the effective properties of complex systems.

Mauri, Roberto

342

Mitochondrial threshold effects.  

PubMed Central

The study of mitochondrial diseases has revealed dramatic variability in the phenotypic presentation of mitochondrial genetic defects. To attempt to understand this variability, different authors have studied energy metabolism in transmitochondrial cell lines carrying different proportions of various pathogenic mutations in their mitochondrial DNA. The same kinds of experiments have been performed on isolated mitochondria and on tissue biopsies taken from patients with mitochondrial diseases. The results have shown that, in most cases, phenotypic manifestation of the genetic defect occurs only when a threshold level is exceeded, and this phenomenon has been named the 'phenotypic threshold effect'. Subsequently, several authors showed that it was possible to inhibit considerably the activity of a respiratory chain complex, up to a critical value, without affecting the rate of mitochondrial respiration or ATP synthesis. This phenomenon was called the 'biochemical threshold effect'. More recently, quantitative analysis of the effects of various mutations in mitochondrial DNA on the rate of mitochondrial protein synthesis has revealed the existence of a 'translational threshold effect'. In this review these different mitochondrial threshold effects are discussed, along with their molecular bases and the roles that they play in the presentation of mitochondrial diseases.

Rossignol, Rodrigue; Faustin, Benjamin; Rocher, Christophe; Malgat, Monique; Mazat, Jean-Pierre; Letellier, Thierry

2003-01-01

343

System Effectiveness Model Formulation  

SciTech Connect

Evaluation of system effectiveness has numerous pitfalls. System objectives may be poorly defined, may shift during the system life or may be hard to quantify. Further, individual perceptions of the quantifications may differ. Whatever the cause, system effectiveness has been an elusive term to quantitatively define. The proposed model presents a quantitative system effectiveness model and establishes a utilitarian approach for its use with the illustrative application to a nuclear safeguards system. The model uses the Type I and Type II statistical error rates as input to the component or subsystem effectiveness calculation which, when combined using a utilitarian methodology, quantify the overall system effectiveness. The methodology will use a survey of expert judgment to determine the relative importance of the individual subsystems through a statistically designed web survey. The web based survey will be available to nuclear material protection, control, and accounting experts attending the 2008 INMM conference. This model and methodology will provide a repeatable quantifiable measure for any system but in this case a simple safeguards system is used as an example.

Coates, Cameron W [ORNL; Jackson, Denise F [ORNL

2008-01-01

344

Liner environment effects study  

NASA Technical Reports Server (NTRS)

The Liner Environment Effects Study Program is aimed at establishing a broad heat transfer data base under controlled experimental conditions by quantifying the effects of the combustion system conditions on the combustor liner thermal loading and on the flame radiation characteristics. Five liner concepts spanning the spectrum of liner design technology from the very simple to the most advanced concepts are investigated. These concepts comprise an uncooled liner, a conventional film cooled liner, an impingement/film cooled liner, a laser drilled liner approaching the concept of a porous wall, and a siliconized silicon carbide ceramic liner. Effect of fuel type is covered by using fuels containing 11.8, 12.8, and 14% hydrogen. Tests at 100, 200, and 300 psia provide a basis for evaluating the effect of pressure on the heat transfer. The effects of the atomization quality and spray characteristics are examined by varying the fuel spray Sauter mean diameter and the spray angle. Additional varied parameters include reference velocity, a wide range of equivalence ratio, cooling flow rate, coolant temperature and the velocity of the coolant stream on the backside of the liner.

Venkataramani, K. S.; Ekstedt, E. E.

1984-01-01

345

Critical effects and exposure limits.  

PubMed

The use of critical effects in the determination of occupational exposure limits (OELs) in Sweden is subjected to a statistical study. Many of the present OELs are high in relation to known no-effect levels and effect levels, and the degree of protection has a surprisingly weak correlation with the seriousness of the adverse effect. Several proposals for improved procedures are put forward. One of these is to supplement the concept of critical effects with that of dominant effects. A dominant effect of a substance is a health effect that is at some concentration the most serious health effect. PMID:9202490

Hansson, S O

1997-04-01

346

Effective Nutritional Supplement Combinations  

NASA Astrophysics Data System (ADS)

Few supplement combinations that are marketed to athletes are supported by scientific evidence of their effectiveness. Quite often, under the rigor of scientific investigation, the patented combination fails to provide any greater benefit than a group given the active (generic) ingredient. The focus of this chapter is supplement combinations and dosing strategies that are effective at promoting an acute physiological response that may improve/enhance exercise performance or influence chronic adaptations desired from training. In recent years, there has been a particular focus on two nutritional ergogenic aids—creatine monohydrate and protein/amino acids—in combination with specific nutrients in an effort to augment or add to their already established independent ergogenic effects. These combinations and others are discussed in this chapter.

Cooke, Matt; Cribb, Paul J.

347

Aviation noise effects  

NASA Astrophysics Data System (ADS)

This report summarizes the effects of aviation noise in many areas, ranging from human annoyance to impact on real estate values. It also synthesizes the findings of literature on several topics. Included in the literature were many original studies carried out under FAA and other Federal funding over the past two decades. Efforts have been made to present the critical findings and conclusions of pertinent research, providing, when possible, a bottom line conclusion, criterion or perspective. Issues related to aviation noise are highlighted, and current policy is presented. Specific topic addressed include: annoyance; Hearing and hearing loss; noise metrics; human response to noise; speech interference; sleep interference; non-auditory health effects of noise; effects of noise on wild and domesticated animals; low frequency acoustical energy; impulsive noise; time of day weightings; noise contours; land use compatibility; and real estate values. This document is designed for a variety of users, from the individual completely unfamiliar with aviation noise to experts in the field.

Newman, J. S.; Beattie, K. R.

1985-03-01

348

Effective Documentation Tools  

NASA Technical Reports Server (NTRS)

Quality assurance programs provide a very effective means to monitor and evaluate medical care. Quality assurance involves: (1) Identify a problem; (2) Determine the source and nature of the problem; (3) Develop policies and methods to effect improvement; (4) Implement those polices; (5) Monitor the methods applied; and (6) Evaluate their effectiveness. Because this definition of quality assurance so closely resembles the Nursing Process, the health unit staff was able to use their knowledge of the nursing process to develop many forms which improve the quality of patient care. These forms include the NASA DFRC Service Report, the occupational injury form (Incident Report), the patient survey (Pre-hospital Evaluation/Care Report), the Laboratory Log Sheet, the 911 Run Sheet, and the Patient Assessment Stamp. Examples and steps which are followed to generate these reports are described.

Sleboda, Claire

1997-01-01

349

Heavy rain effects  

NASA Technical Reports Server (NTRS)

This paper summarizes the current state of knowledge of the effect of heavy rain on airplane performance. Although the effects of heavy rain on airplane systems and engines are generally known, only recently has the potential aerodynamic effect of heavy rain been recognized. In 1977 the United States Federal Aviation Administration (FAA) conducted a study of 25 aircraft accidents and incidents which occurred between 1964 and 1976 in which low-altitude wind shear could have been a contributing factor. Of the 25 cases (23 approach or landing and 2 take-off) in the study, ten cases had occurred in a rain environment, and in five cases these were classified as intense or heavy rain encounters. These results led to the reconsideration of high-intensity, short-duration rainfall as a potential weather-related aircraft safety hazard, particularly in the take-off and/or approach phases of flight.

Dunham, R. Earl, Jr.

1994-01-01

350

Giving effective presentations.  

PubMed

Apprehension about oral communication, or public speaking is rated as the number one fear among most individuals. Developing skill in, and comfort with, public speaking is important whether we are presenting oral reports and proposals, responding to questions, or training co-workers. Effective speakers are able to communicate information in a way that stimulates interest, helps the audience to understand and remember, and influences attitudes and behaviours. Many of us think that effective speakers are born rather than made. In truth most successful speakers work hard and invest a great deal of time and effort in to improving their speaking capabilities. Effective public speaking is a learned skill and activity that requires lots of practice. Like other learned skills, having a strategy with clear action steps can help you achieve your goal. PMID:15116467

Englehart, Nadine

2004-03-01

351

Disentangling the EMC effect  

NASA Astrophysics Data System (ADS)

The deep inelastic scattering cross section for scattering from bound nucleons differs from that of free nucleons. This phenomena, first discovered 30 years ago, is known as the EMC effect and is still not fully understood. Recent analysis of world data showed that the strength of the EMC effect is linearly correlated with the relative amount of Two-Nucleon Short Range Correlated pairs (2N-SRC) in nuclei. The latter are pairs of nucleons whose wave functions overlap, giving them large relative momentum and low center of mass momentum, where high and low is relative to the Fermi momentum of the nucleus. The observed correlation indicates that the EMC effect, like 2N-SRC pairs, is related to high momentum nucleons in the nucleus. This paper reviews previous studies of the EMC-SRC correlation and studies its robustness. It also presents a planned experiment aimed at studying the origin of this EMC-SRC correlation.

Piasetzky, E.; Hen, O.; Weinstein, L. B.

2013-10-01

352

Habituation of reinforcer effectiveness.  

PubMed

In this paper we propose an integrative model of habituation of reinforcer effectiveness (HRE) that links behavioral- and neural-based explanations of reinforcement. We argue that HRE is a fundamental property of reinforcing stimuli. Most reinforcement models implicitly suggest that the effectiveness of a reinforcer is stable across repeated presentations. In contrast, an HRE approach predicts decreased effectiveness due to repeated presentation. We argue that repeated presentation of reinforcing stimuli decreases their effectiveness and that these decreases are described by the behavioral characteristics of habituation (McSweeney and Murphy, 2009; Rankin etal., 2009). We describe a neural model that postulates a positive association between dopamine neurotransmission and HRE. We present evidence that stimulant drugs, which artificially increase dopamine neurotransmission, disrupt (slow) normally occurring HRE and also provide evidence that stimulant drugs have differential effects on operant responding maintained by reinforcers with rapid vs. slow HRE rates. We hypothesize that abnormal HRE due to genetic and/or environmental factors may underlie some behavioral disorders. For example, recent research indicates that slow-HRE is predictive of obesity. In contrast ADHD may reflect "accelerated-HRE." Consideration of HRE is important for the development of effective reinforcement-based treatments. Finally, we point out that most of the reinforcing stimuli that regulate daily behavior are non-consumable environmental/social reinforcers which have rapid-HRE. The almost exclusive use of consumable reinforcers with slow-HRE in pre-clinical studies with animals may have caused the importance of HRE to be overlooked. Further study of reinforcing stimuli with rapid-HRE is needed in order to understand how habituation and reinforcement interact and regulate behavior. PMID:24409128

Lloyd, David R; Medina, Douglas J; Hawk, Larry W; Fosco, Whitney D; Richards, Jerry B

2014-01-01

353

Handbook of radiation effects  

SciTech Connect

This book emphasizes radiation effects on solid state devices from exposure to the types of radiation found outside the atmosphere (in space, or in the vicinity of an exploding nuclear device). It contains a basic study of radiation shielding of payload components for payloads in space and specifically covers radiation effects on minority and majority carriers, optical media and organic materials. It also includes some basic information on radioactivity, monitoring equipment and different types of radiation fields. This book is not oriented toward health physics.

Holmes-Siedle, A.; Adams, L.

1993-12-31

354

Photostimulated even acoustoelectric effect  

NASA Astrophysics Data System (ADS)

Photostimulated photogalvanic (PG) and acoustogalvanic (AG) currents in a semiconductor placed in the field of two linearly polarized electromagnetic waves with frequencies Omega sub 1 = 2Omega sub 2 are analyzed. These currents affect the probability of electron scattering and the HF acoustic flux field. Under specified double laser illumination the system comprising an electron gas and photons becomes noncentrosymmetric, which leads to the PG and AG effects. The AG effect represents a contribution to the acoustoelectric current that is linear according to intensity and even according to the acoustic wave vector.

Shmelev, G. M.; Shon, N. Kh.; Tsurkan, G. I.

1985-02-01

355

Magnon gap formation and charge density wave effect on thermoelectric properties in SmNiC2 compound  

NASA Astrophysics Data System (ADS)

We studied the magnetic, electrical, and thermal properties of polycrystalline compound of SmNiC2. The electrical resistivity and magnetization measurement show the interplay between the charge density wave at TCDW = 157 K and the ferromagnetic ordering of Tc = 18 K. Below the ferromagnetic transition temperature, we observed the magnon gap formation of 4.3 ˜ 4.4 meV by ?(T) and Cp(T) measurements. The charge density wave is attributed to the increase of Seebeck coefficient resulting in the increase of power factor S^2?. The thermoelectric figure-of-merit ZT significantly increases due to the increase of power factor at TCDW = 157 K. Here we argue that the competing interaction between electron-phonon and electron-magnon couplings exhibits the unconventional behavior of electrical and thermal properties. This research was supported by Basic Science Research Program (2011-0021335), Nano-Material Technology Development Program (2011-0030147), and Mid-career Research Program (Strategy) (No. 2012R1A2A1A03005174) through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology.

Kim, Jin-Hee; Rhyee, Jong-Soo; Kwon, Yong Seung

2013-03-01

356

Effects of Second Phase Yb5Sb3 on the Thermoelectric Properties of YbAl3  

NASA Astrophysics Data System (ADS)

The compound YbAl3 exhibits a very high power factor but also rather a large thermal conductivity, leading to a low figure of merit. The second phase Yb5Sb3 was introduced in the YbAl3 matrix to reduce its thermal conductivity. The composites (YbAl3)1- x (Yb5Sb3) x with x = 0, 0.01, 0.05, 0.10, and 0.20 were synthesized by high frequency induction melting, annealing treatment, and spark plasma sintering. The thermoelectric properties of the composites were evaluated. The composites are of n-type conduction. The pure YbAl3 obtained in this work shows a high power factor of 11,500 ?W m-1 K-2 but also a high thermal conductivity of 19.6 W m-1 K-1. However, the existence of Yb5Sb3 compound in the YbAl3 matrix enhances the electrical resistivity and the absolute Seebeck coefficient of the composite, but significantly reduces its thermal conductivity in the temperature range considered, thereby enhancing the figure of merit. The highest ZT value of 0.23 may be obtained in the sample (YbAl3)0.95(Yb5Sb3)0.05 at room temperature, which is apparently higher than that of pure YbAl3.

Li, J. Q.; Liu, X. Y.; Li, Y.; Deng, J. F.; Ye, R. F.; Song, S. H.; Liu, F. S.; Ao, W. Q.

2014-04-01

357

Effect of high temperature annealing on the thermoelectric properties of GaP doped SiGe  

NASA Technical Reports Server (NTRS)

Silicon-germanium alloys doped with GaP are used for thermoelectric energy conversion in the temperature range 300-1000 C. The conversion efficiency depends on Z = S-squared/rho lambda, a material's parameter (the figure of merit), where S is the Seebeck coefficient, rho is the electrical resistivity and lambda is the thermal conductivity. The annealing of several samples in the temperature range of 1100-1300 C resulted in the power factor P (= S-squared/rho) increasing with increased annealing temperature. This increase in P was due to a decrease in rho which was not completely offset by a drop in S-squared suggesting that other changes besides that in the carrier concentration took place. SEM and EDX analysis of the samples indicated the formation of a Ga-P-Ge rich phase as a result of the annealing. It is speculated that this phase is associated with the improved properties. Several reasons which could account for the improvement in the power factor of annealed GaP doped SiGe are given.

Vandersande, Jan W.; Wood, Charles; Draper, Susan

1987-01-01

358

Health Effects of Noise Pollution  

MedlinePLUS

... effects of noise pollution Health effects of noise pollution People of all ages, including children, teens, young ... noises around them. The health effects of noise pollution include: Hearing loss. Noise-induced hearing loss usually ...

359

Convergence of conduction bands as a means of enhancing thermoelectric performance of n-type Mg2Si(1-x)Sn(x) solid solutions.  

PubMed

Mg(2)Si and Mg(2)Sn are indirect band gap semiconductors with two low-lying conduction bands (the lower mass and higher mass bands) that have their respective band edges reversed in the two compounds. Consequently, for some composition x, Mg(2)Si(1-x)Sn(x) solid solutions must display a convergence in energy of the two conduction bands. Since Mg(2)Si(1-x)Sn(x) solid solutions are among the most prospective of the novel thermoelectric materials, we aim on exploring the influence of such a band convergence (valley degeneracy) on the Seebeck coefficient and thermoelectric properties in a series of Mg(2)Si(1-x)Sn(x) solid solutions uniformly doped with Sb. Transport measurements carried out from 4 to 800 K reveal a progressively increasing Seebeck coefficient that peaks at x=0.7. At this concentration the thermoelectric figure of merit ZT reaches exceptionally large values of 1.3 near 700 K. Our first principles calculations confirm that at the Sn content x?0.7 the two conduction bands coincide in energy. We explain the high Seebeck coefficient and ZT values as originating from an enhanced density-of-states effective mass brought about by the increased valley degeneracy as the two conduction bands cross over. We corroborate the increase in the density-of-states effective mass by measurements of the low temperature specific heat. The research suggests that striving to achieve band degeneracy by means of compositional variations is an effective strategy for enhancing the thermoelectric properties of these materials. PMID:22680741

Liu, Wei; Tan, Xiaojian; Yin, Kang; Liu, Huijun; Tang, Xinfeng; Shi, Jing; Zhang, Qingjie; Uher, Ctirad

2012-04-20

360

Enhanced thermoelectric performance in zinc substituted p-type filled skutterudites CeFe{sub 4-x}Zn{sub x}Sb{sub 12}  

SciTech Connect

In this study, Zn-substituted polycrystalline skutterudites CeFe{sub 4-x}Zn{sub x}Sb{sub 12} (x=0, 0.05, 0.1, 0.2, 0.3) were successfully prepared by a traditional melting-annealing method. The solubility of Zn in Fe site is {approx}1.2%, exceeding which trace amount of ZnSb phase can be detected in the XRD. This ZnSb impurity phase, with size of several hundred nanometers for the sample with x=0.2 but showing surprisingly small size of {approx}10 nm for the sample with x=0.3, selectively distributes on the grain boundaries. In particular, the introduction of Zn in Fe site effectively improves the Seebeck coefficient in a manner of enhancement in hole effective mass, but it has negligible influence on both electrical and thermal conductivities though the hole concentration is increased. Consequently the corresponding improvement in power factor leads to an improved thermoelectric figure of merit (ZT) of 0.9 at 800 K for the sample with x=0.1, which is {approx}15% higher than that of Zn-free sample. This study demonstrates a favorable effect of Zn iso-substitution and opens a new strategy to improve the thermoelectric properties of p-type Fe-based skutterudites beyond the sole phonon engineering. - Graphical abstract: (a)-(c) ZnSb nanoinclusions emerge when Zn exceeds its solubility limit. (d), (e) The introduction of Zn boosts the Seebeck coefficient and thus enhances the ZT value. Highlights: Black-Right-Pointing-Pointer Zn is successfully employed to substitute Fe atom for the first time. Black-Right-Pointing-Pointer ZnSb nanoinclusions emerge when Zn exceeds its solubility limit {approx}0.12. Black-Right-Pointing-Pointer The introduction of Zn boosts the Seebeck coefficient and enhances the ZT value.

Tan Gangjian; Wang Shanyu; Li Han; Yan Yonggao [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Luoshi Road 122, Hongshan district, Wuhan 430070 (China); Tang Xinfeng, E-mail: tangxf@whut.edu.cn [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Luoshi Road 122, Hongshan district, Wuhan 430070 (China)

2012-03-15

361

Convergence of Conduction Bands as a Means of Enhancing Thermoelectric Performance of n-Type Mg2Si1-xSnx Solid Solutions  

NASA Astrophysics Data System (ADS)

Mg2Si and Mg2Sn are indirect band gap semiconductors with two low-lying conduction bands (the lower mass and higher mass bands) that have their respective band edges reversed in the two compounds. Consequently, for some composition x, Mg2Si1-xSnx solid solutions must display a convergence in energy of the two conduction bands. Since Mg2Si1-xSnx solid solutions are among the most prospective of the novel thermoelectric materials, we aim on exploring the influence of such a band convergence (valley degeneracy) on the Seebeck coefficient and thermoelectric properties in a series of Mg2Si1-xSnx solid solutions uniformly doped with Sb. Transport measurements carried out from 4 to 800 K reveal a progressively increasing Seebeck coefficient that peaks at x=0.7. At this concentration the thermoelectric figure of merit ZT reaches exceptionally large values of 1.3 near 700 K. Our first principles calculations confirm that at the Sn content x?0.7 the two conduction bands coincide in energy. We explain the high Seebeck coefficient and ZT values as originating from an enhanced density-of-states effective mass brought about by the increased valley degeneracy as the two conduction bands cross over. We corroborate the increase in the density-of-states effective mass by measurements of the low temperature specific heat. The research suggests that striving to achieve band degeneracy by means of compositional variations is an effective strategy for enhancing the thermoelectric properties of these materials.

Liu, Wei; Tan, Xiaojian; Yin, Kang; Liu, Huijun; Tang, Xinfeng; Shi, Jing; Zhang, Qingjie; Uher, Ctirad

2012-04-01

362

Lightning Physics and Effects  

Microsoft Academic Search

Lightning Physics and Effects is not a lightning book; it is a lightning encyclopedia. Rarely in the history of science has one contribution covered a subject with such depth and thoroughness as to set the enduring standard for years, perhaps even decades, to come. This contribution covers all aspects of lightning, including lightning physics, lightning protection, and the interaction of

Richard E. Orville

2004-01-01

363

Effectively Communicating Qualitative Research  

ERIC Educational Resources Information Center

This article is a guide for counseling researchers wishing to communicate the methods and results of their qualitative research to varied audiences. The authors posit that the first step in effectively communicating qualitative research is the development of strong qualitative research skills. To this end, the authors review a process model for…

Ponterotto, Joseph G.; Grieger, Ingrid

2007-01-01

364

Cardiovascular effects of tadalafil  

Microsoft Academic Search

To determine the effects of tadalafil on the cardiovascular system, safety assessments were performed on a database of >4,000 subjects who received tadalafil in >60 clinical pharmacology, phase 2, phase 3, and open-label studies. In healthy subjects, tadalafil resulted in small changes in blood pressure, which are not believed to be clinically relevant. Daily administration of tadalafil 20 mg for

Robert A Kloner; Malcolm Mitchell; Jeffrey T Emmick

2003-01-01

365

Measuring Institutional Effectiveness.  

ERIC Educational Resources Information Center

The measurement of institutional effectiveness involves a systematic comparison of organizational purpose and performance. For community colleges, organizational purpose can be defined in terms of providing access to education, realizing student achievement, promoting student development, or addressing social needs. If all four purposes are…

Macomb County Community Coll., Warren, MI.

366

High Density Fuel Effects.  

National Technical Information Service (NTIS)

The purpose of this program was to determine, by combustor rig tests and data evaluation, the effects of the high density fuel properties on the performance and durability of the Allison T56-A-15 combustion system. Four high density fuels in addition to b...

H. C. Mongia N. K. Rizk P. T. Ross V. L. Oechsie

1988-01-01

367

Effective Thinking Outdoors.  

ERIC Educational Resources Information Center

Effective Thinking Outdoors (ETO) is an organization that teaches thinking skills and strategies via significant outdoor experiences. Identifies the three elements of thinking as creativity, play, and persistence; presents a graphic depiction of the problem-solving process and aims; and describes an ETO exercise, determining old routes of travel…

Hyde, Rod

1997-01-01

368

Effective View Navigation  

Microsoft Academic Search

In view navigation a user moves about an information structure by selecting something in the current view of the structure. This paper explores the implications of rudimentary requirements for effective view navigation, namely that, despite the vastness of an information structure, the views must be small, moving around must not take too many steps and the route to any target

George W. Furnas

1997-01-01

369

Commentary: Expanding on Effectiveness  

ERIC Educational Resources Information Center

Atkins, Graczyk, Frazier, and Abdul-Adil (2003) make the point that there have been three limitations of mental health services for children and families in low-income, urban settings: (a) accessibility; (b) effectiveness; and (c) sustainability. Their article focuses extensively on improving access and addressing issues of sustainability in…

Pelham, William E., Jr.; Massetti, Greta M.

2003-01-01

370

Interactive Pi Bonding Effects  

NSDL National Science Digital Library

This application demonstrates the effect of pi bonding on the one-electron ligand field splitting in an octahedral. By clicking on the appropriate buttons students can see how D changes when you move from ligands with no pi bonding capability to pi donor and pi acceptor ligands.

371

Camp's "Disneyland" Effect.  

ERIC Educational Resources Information Center

Describes the positive mental, physical, and social growth impacts that the camping experience had on the author, and urges camp program evaluation to plan and implement such changes. Sidebar lists steps of effective evaluation: program goals and objectives, goals of evaluation, implementation of evaluation, data analysis, and findings and…

Renville, Gary

1999-01-01

372

BIOLOGICAL EFFECTS OF MANGANESE  

EPA Science Inventory

The biological effects of manganese were studied in a town on the coast of Dalmatia in which a ferromanganese plant has been operating since before World War II. The study focused on the question of whether the exposure to manganese can cause a higher incidence of respiratory dis...

373

EFFECTS ON SALTWATER ORGANISMS  

EPA Science Inventory

The literature review summarizes current data on the effects of pesticides and metals on marine organisms, aquatic environmental research methods, bioaccumulation of pollutants by estuarine and marine organisms and in water/sediment residues and biota. Results of studies of the e...

374

Angular Talbot effect  

NASA Astrophysics Data System (ADS)

We predict the possibility of observing integer and fractional self-imaging (Talbot) phenomena on the discrete angular spectrum of periodic diffraction gratings illuminated by a suitable spherical wave front. Our predictions are experimentally validated, reporting what we believe to be the first observation of self-imaging effects in the far-field diffraction regime.

Azaña, José; Guillet de Chatellus, Hugues

2014-05-01

375

FIELD DISPERSANT EFFECTIVENESS TEST  

EPA Science Inventory

The EPA's OHMSETT facility has developed a rapid field test that includes some of the theoretical aspects and conditions of dispersion at sea. This Field Dispersant Effectiveness Test (FDET) has been used to evaluate the dispersibility of various commonly-transported oils and mak...

376

Physiological effects of hypnosis  

Microsoft Academic Search

There are many studies indicating that sensory, circulatory, gastrointestinal, and cutaneous functions can be altered by means of hypnosis. There also are many studies indicating that similar physiological effects can be produced by symbolic stimulation without hypnosis. The assumption that hypnotic behavior is a function of the trance state is open to question. From Psyc Abstracts 36:01:3II90B.

Theodore Xenophon Barber

1961-01-01

377

Cost Effective Prototyping  

NASA Technical Reports Server (NTRS)

This laboratory exercise seeks to develop a cost effective prototype development. The exercise has the potential of linking part design, CAD, mold development, quality control, metrology, mold flow, materials testing, fixture design, automation, limited parts production and other issues as related to plastics manufacturing.

Wickman, Jerry L.; Kundu, Nikhil K.

1996-01-01

378

Crossfield effect at fluxgate  

Microsoft Academic Search

The magnetic field transverse to the sensing axis may affect the performance of magnetic sensors. In the case of fluxgates, this effect is not as dramatic as it is for AMR sensors, but it still may cause errors up to 40 nT in the Earth's field. We performed measurements on voltage output fluxgate sensors of various constructions. Ring-cores are the

P Ripka; S. W Billingsley

2000-01-01

379

The offline production effect.  

PubMed

People remember words they say aloud better than ones they do not, a result called the production effect. The standing explanation for the production effect is that producing a word renders it distinctive in memory and thus memorable at test. Whereas it is now clear that motoric production benefits remembering over nonproduction, and that more intense motoric production benefits remembering to a greater extent than less intense motoric production, there has been no comparison of the memorial benefit conferred by motoric versus imagined production. One reason for the gap is that the standard production-by-vocalization procedure confounds the analysis. To make the comparison, we used a production-by-typing procedure and tested memory for words that people typed, imagined typing, and did not type. Whereas participants remembered the words that they typed and imagined typing better than words that they did not, they remembered the words they typed better than the ones they imagined typing; an advantage that was consistent over tests of recognition memory and source discrimination. We conclude that motoric production is a sufficient and facilitative (but not a necessary) condition to observe the production effect. We explain our results by a sensory feedback account of the production effect and sketch a computational framework to implement that approach. PMID:24364810

Jamieson, Randall K; Spear, Jackie

2014-03-01

380

Aviation noise effects  

Microsoft Academic Search

This report summarizes the effects of aviation noise in many areas, ranging from human annoyance to impact on real estate values. It also synthesizes the findings of literature on several topics. Included in the literature were many original studies carried out under FAA and other Federal funding over the past two decades. Efforts have been made to present the critical

J. S. Newman; K. R. Beattie

1985-01-01

381

Learning to Effect.  

ERIC Educational Resources Information Center

This book presents 14 papers which discuss contemporary issues of curriculum change and instructional effectiveness in higher education primarily from a British perspective. Papers address curriculum purpose, curriculum delivery, and curriculum impact on the wider society. In addition, the book covers experiential learning, skills and training,…

Barnett, Ronald, Ed.

382

Surface Effects Skimmer Developments.  

National Technical Information Service (NTIS)

This experimental program investigated the use of a Surface Effects Skimmer in removing thin film oil slicks spread over large water areas by fast currents. This new skimmer uses a directed air jet to separate and lift spilled oil from the surface of the ...

N. P. Trentacoste

1975-01-01

383

Tips for Effective Management  

ERIC Educational Resources Information Center

School business officials' days are filled with numbers and reports--audits, balance sheets, check registers, financial statements, journal entries, vouchers, and warrant reports, just to name a few. Those are all important tools that school business officers use to manage the financial resources of the district effectively. However, they are also…

Supple, Kevin F.

2009-01-01

384

Pleiotropic effects of incretins  

PubMed Central

Drugs that augment the incretin system [glucagon like peptide (GLP) agonists and dipeptidyl peptidase-4 (DPP-4) inhibitors] represent a novel class of anti-hyperglycemic agents that have shown to improve the health and survival of beta-cells (improvement in postprandial hyperglycemia) and suppress glucagon (improvement in fasting hyperglycemia). The incretins represent a large family of molecules referred to as the “glucagon superfamily of peptide hormones” of which more than 90% of the physiological effects of incretins are accomplished by GLP-17-37 and GLP17-36 amide and gastric insulinotropic peptide (GIP). GLP-1 mediates its effects via the GLP-1 receptor, which has a wide tissue distribution [pancreas, lung, heart, vascular smooth muscle cells, endothelial cells, macrophages and monocytes, kidney, gastrointestinal tract (stomach and intestine), central nervous system (neoortex, cerebellum, hypothalamus, hippocampus, brainstem nucleus tractus solitarius) and peripheral nervous system]. This would imply that the incretin system has effects outside the pancreas. Over time data has accumulated to suggest that therapies that augment the incretin system has beneficial pleiotrophic effects. The incretins have shown to possess a cardiac-friendly profile, preserve neuronal cells and safeguard from neuronal degeneration, improve hepatic inflammation and hepatosteatosis, improve insulin resistance, promote weight loss and induce satiety. There is growing evidence that they may also be renoprotective promoting wound healing and bone health.

Gupta, Vishal

2012-01-01

385

Effectiveness of Median Barriers.  

National Technical Information Service (NTIS)

The objective of this study was to ascertain whether the employment of physical barriers within the highway median is effective in promoting highway safety. An uncontrolled before and after study of 54.2 miles of urban freeway in California was conducted ...

R. T. Johnson

1964-01-01

386

Lorenz Attractor -- Butterfly Effect  

NSDL National Science Digital Library

The "Butterfly Effect", or more technically the "sensitive dependence on initial conditions", is the essence of chaos. This is illustrated an applet of the Lorenz Attractor. The demonstration shows a graphical representation of the time variation of three variables X(t),Y(t) and Z(t), coupled by non-linear evolution equations.

Michael Cross, Cal T.

387

Space Environmental Effects Knowledgebase  

NASA Technical Reports Server (NTRS)

This report describes the results of an NRA funded program entitled Space Environmental Effects Knowledgebase that received funding through a NASA NRA (NRA8-31) and was monitored by personnel in the NASA Space Environmental Effects (SEE) Program. The NASA Project number was 02029. The Satellite Contamination and Materials Outgassing Knowledgebase (SCMOK) was created as a part of the earlier NRA8-20. One of the previous tasks and part of the previously developed Knowledgebase was to accumulate data from facilities using QCMs to measure the outgassing data for satellite materials. The main object of this current program was to increase the number of material outgassing datasets from 250 up to approximately 500. As a part of this effort, a round-robin series of materials outgassing measurements program was also executed that allowed comparison of the results for the same materials tested in 10 different test facilities. Other programs tasks included obtaining datasets or information packages for 1) optical effects of contaminants on optical surfaces, thermal radiators, and sensor systems and 2) space environmental effects data and incorporating these data into the already existing NASA/SEE Knowledgebase.

Wood, B. E.

2007-01-01

388

Microcircuit Radiation Effects Databank.  

National Technical Information Service (NTIS)

Radiation test data submitted by many testers is collated to serve as a reference for engineers who are concerned with and have some knowledge of the effects of the natural radiation environment on microcircuits. Total dose damage information and single e...

1983-01-01

389

Cardiovascular effects of melanocortins  

Microsoft Academic Search

Melanocortins (MSH's) are three structurally related peptides derived from proopiomelanocortin. They regulate several physiologic functions including energy metabolism, appetite, and inflammation. Recent work in rodents has also identified important effects of MSH's, particularly ?-MSH, on sodium metabolism and blood pressure regulation. Normal rats and mice respond to a high sodium diet with an increase in the plasma concentration of ?-MSH,

Michael H. Humphreys; Xi-Ping Ni; David Pearce

2011-01-01

390

(Limiting the greenhouse effect)  

Microsoft Academic Search

Traveler attended the Dahlem Research Conference organized by the Freien Universitat, Berlin. The subject of the conference was Limiting the Greenhouse Effect: Options for Controlling Atmospheric COâ Accumulation. Like all Dahlem workshops, this was a meeting of scientific experts, although the disciplines represented were broader than usual, ranging across anthropology, economics, international relations, forestry, engineering, and atmospheric chemistry. Participation by

Rayner

1991-01-01

391

Noise: Effects and Control.  

National Technical Information Service (NTIS)

The type and degree of the effects on man of exposure to high-intensity noise is determined primarily by (1) the type of noise, i.e., continuous or interrupted, (2) the spectrum of the noise, i.e., low or high pitch, (3) intensity (loudness), (4) length o...

K. K. Neely

1965-01-01

392

The Contrail Effect  

NSDL National Science Digital Library

NOVA's The Contrail Effect describes how contrails form and how humidity determines how long they last. The webpage goes on to describe the study during the days of clear skies, without contrails, following 9/11. Three satellite images of contrail patterns are provided.

Foundation, Wgbh E.

2011-09-15

393

Documentation: Effective AND Literate  

Microsoft Academic Search

The purpose of this paper is to show how documentation can be literate, in a stylistic sense, and still be effective. Literate prose is a powerful tool that, when properly used in computer documentation, can take advantage of the full power of the English language. This does not mean that all computer documentation must or can read like a Nobel

Paul S. Burdett Jr.

1985-01-01

394

Effects of acoustic sources  

Microsoft Academic Search

An experiment was conducted to determine the effect of acoustics on the laminar flow on the side of a nacelle. A flight test was designed to meet this goal and a brief review of the purpose is given. A nacelle with a significant length of laminar flow was mounted on the wing of NASA OV-1. Two noise sources are also

James A. Schoenster; Michael G. Jones

1987-01-01

395

Effective resonance levels  

Microsoft Academic Search

A method based on the use of effective resonance integrals or group cross sections with resonance self-shielding factors has come into extensive use in calculations of resonance absorption in homogeneous systems. An attempt is made to extend the subgroup treatment, which was initially formulated for the region of forbidden resonances, to the allowed region as applicable to heterogeneous media. A

B. P. Kochurov

1986-01-01

396

Field effect transistors  

Microsoft Academic Search

A patent is claimed for an invention relating to Metal Insulator Semiconductor Field Effect Transistors (MISFECTs) in which organic polymers are used as the semiconducting component. The FET has a gate electrode deposited on a substrate and separated from a semiconducting layer by an insulating layer, the semiconducting layer being provided with two terminals to allow passage of an electric

Philip Charles Allen; Richard Henry Friend; Jeremy Henly Burroughes

1988-01-01

397

Exploring the Lotus Effect  

NSDL National Science Digital Library

Students test and observe the "self-cleaning" lotus effect using a lotus leaf and cloth treated with a synthetic lotus-like superhydrophobic coating. They also observe the Wenzel and Cassie Baxter wetting states by creating and manipulating condensation droplets on the leaf surface. They consider the real-life engineering applications for these amazing water-repellent and self-cleaning properties.

NSF CAREER Award and RET Program, Mechanical Engineering and Material Science,

398

Cardiovascular effects of alcohol.  

PubMed Central

The effects of alcohol on the heart include modification of the risk of coronary artery disease, the development of alcoholic cardiomyopathy, exacerbation of conduction disorders, atrial and ventricular dysrhythmias, and an increased risk of hypertension, hemorrhagic stroke, infectious endocarditis, and fetal heart abnormalities.

Davidson, D M

1989-01-01

399

DCPS Effective Schools Framework  

ERIC Educational Resources Information Center

DCPS is committed to providing "all" students with the caliber of education they deserve. The goal of the DCPS Effective Schools Framework is to ensure that every child, in every classroom, has access to a high-quality and engaging standards-based instructional program, and that all school supports are aligned to support teaching and learning. The…

District of Columbia Public Schools, 2009

2009-01-01

400

Alexandrite effect spectropyrometer  

NASA Astrophysics Data System (ADS)

Alexandrite crystal is commonly used for making alexandrite laser, and it also has a less-known phenomenon called the alexandrite effect that refers to the color change between different light sources. A novel spectropyrometer for temperature measurement of a radiating body utilizing the alexandrite effect is introduced. The alexandrite effect method for temperature measurement is based on the relationship between the temperature of blackbody and the hue-angle in the CIELAB color space. The alexandrite effect spectropyrometer consists of an optical probe, a spectrometer, a computer, and an alexandrite filter. It measures the spectral power distribution of a radiating body through the alexandrite filter, calculates the hue-angle, and determines the temperature. The spectropyrometer is suitable for temperature measurement of any radiating body with or without spectral lines in its spectral power distribution from 1000 K to 100000 K. The spectropyrometer is particularly useful for high to ultrahigh temperature measurement of any radiating bodies with spectral line emissions, such as electric arcs and discharges, plasmas, and high temperature flames.

Liu, Yan

2006-08-01

401

Confirming Testlet Effects  

ERIC Educational Resources Information Center

A testlet is a cluster of items that share a common passage, scenario, or other context. These items might measure something in common beyond the trait measured by the test as a whole; if so, the model for the item responses should allow for this testlet trait. But modeling testlet effects that are negligible makes the model unnecessarily…

DeMars, Christine E.

2012-01-01

402

Effects of New Technologies.  

ERIC Educational Resources Information Center

This group of articles studies the effects of microelectronics technologies on the world of work and on the social and economic life in general. These studies are related to several industrial nations and are also concerned with the international division of labor. (SSH)

Social and Labour Bulletin, 1983

1983-01-01

403

Effective classical partition functions  

NASA Astrophysics Data System (ADS)

We present a method by which a quantum-mechanical partition function can be approximated from below by an effective classical partition function. The associated potential is obtained by a simple smearing procedure. For a strongly anharmonic oscillator and a double-well potential, the lowest approximation gives a free energy which is accurate to a few percent, even at zero temperature.

Feynman, R. P.; Kleinert, H.

1986-12-01

404

Determinants of Managerial Effectiveness.  

ERIC Educational Resources Information Center

Factors which contribute to managerial effectiveness can be grouped into four major categories: (1) personal characteristics of the individual manager; (2) managerial functions or the managerial process; (3) the various components of the organizational environment; and (4) the outcomes or results of the managerial process. (Author)

Foxley, Cecelia H.

1980-01-01

405

Knowledge Sharing Effectiveness Measurement  

Microsoft Academic Search

Knowledge would be considered as important element in knowledge-based economy and it makes a strong competitive advantage in dynamic business environment. In knowledge management, knowledge sharing is the most critical elements of effective knowledge processing. Several studies have been done to explain why people share knowledge and some of them have been mentioned in this paper. The next issue is

B. Zadjabbari; Pornpit Wongthongtham; Farookh Khadeer Hussain

2010-01-01

406

Stern-Gerlach effect  

NSDL National Science Digital Library

This web page illustrates the Stern-Gerlach effect on spin 1/2 particles. Movies and an illustration show the time-dependent properties of wavepackets in an inhomogeneous magnetic field. Examples are given for silver atoms, ions, and electrons.

De Raedt, Hans; Michielsen, Kristel

2010-03-11

407

Facilitating Online Discussions Effectively  

ERIC Educational Resources Information Center

This article presents a synthesis of the theoretical and research literature on facilitating asynchronous online discussions effectively. Online courses need to be designed so that they provide motivation for students to engage in productive discussions and clearly describe what is expected, perhaps in the form of a discussion rubric.…

Rovai, Alfred P.

2007-01-01

408

Explaining Charter School Effectiveness  

ERIC Educational Resources Information Center

This study uses entrance lotteries to explore heterogeneity in the achievement effects of charter schools across demographic groups and between urban and non-urban areas in Massachusetts. The authors develop a framework for interpreting this heterogeneity using both student- and school-level explanatory variables. (Contains 4 tables.)

Angrist, Joshua D.; Pathak, Parag A.; Walters, Christopher R.

2012-01-01

409

Cuing Effect of \\  

Microsoft Academic Search

It is generally acknowledged that alternatives such as none of the above and all of the above should be used sparingly in multiple-choice (MC) items. But the effect that all of the above has on the reliability and validity of an MC item is unclear This study compared the results of a single-response (SRa) item format that included all of

P. H. Harasym; E. J. Leong; C. Violato; R. Brant; F. L. Lorscheider

1998-01-01

410

Matthew Effects for Whom?  

ERIC Educational Resources Information Center

Which children are most at risk of experiencing a Matthew effect in reading? We investigated this question using population-based methodology. First, we identified children entering kindergarten on socio-demographic factors (i.e., gender, race/ethnicity, and socioeconomic status) known to index the relative risks and resources available to them as…

Morgan, Paul L.; Farkas, George; Hibel, Jacob

2008-01-01

411

Teacher Effectiveness: A Position.  

ERIC Educational Resources Information Center

This document summarizes the highlights of research on teacher effectiveness and concludes with recommendations based on a synthesis of this past work. The various methodologies that have been used are discussed, from rating scales to objective observation techniques, such as OScAR and the ecological studies. The major problems in teacher…

Scott, Myrtle

1969-01-01

412

Brain effects of melanocortins.  

PubMed

The melanocortins (alpha, beta and gamma-melanocyte-stimulating hormones: MSHs; adrenocorticotrophic hormone: ACTH), a family of pro-opiomelanocortin (POMC)-derived peptides having in common the tetrapeptide sequence His-Phe-Arg-Trp, have progressively revealed an incredibly wide range of extra-hormonal effects, so to become one of the most promising source of innovative drugs for many, important and widespread pathological conditions. The discovery of their effects on some brain functions, independently made by William Ferrari and David De Wied about half a century ago, led to the formulation of the term "neuropeptide" at a time when no demonstration of the actual production of peptide molecules by neurons, in the brain, was still available, and there were no receptors characterized for these molecules. In the course of the subsequent decades it came out that melanocortins, besides inducing one of the most complex and bizarre behavioural syndromes (excessive grooming, crises of stretchings and yawnings, repeated episodes of spontaneous penile erection and ejaculation, increased sexual receptivity), play a key role in functions of fundamental physiological importance as well as impressive therapeutic effects in different pathological conditions. If serendipity had been an important determinant in the discovery of the above-mentioned first-noticed extra-hormonal effects of melanocortins, many of the subsequent discoveries in the pharmacology of these peptides (feeding inhibition, shock reversal, role in opiate tolerance/withdrawal, etc.) have been the result of a planned research, aimed at testing the "pro-nociceptive/anti-nociceptive homeostatic system" hypothesis. The discovery of melanocortin receptors, and the ensuing synthesis of selective ligands with agonist or antagonist activity, is generating completely innovative drugs for the treatment of a potentially very long list of important and widespread pathological conditions: sexual impotence, frigidity, overweight/obesity, anorexia, cachexia, haemorrhagic shock, other forms of shock, myocardial infarction, ischemia/reperfusion-induced brain damage, neuropathic pain, rheumathoid arthritis, inflammatory bowel disease, nerve injury, toxic neuropathies, diabetic neuropathy, etc. This review recalls the history of these researches and outlines the pharmacology of the extra-hormonal effects of melanocortins which are produced by an action at the brain level (or mainly at the brain level). In our opinion the picture is still incomplete, in spite of being already so incredibly vast and complex. So, for example, several of their effects and preliminary animal data suggest that melanocortins might be of concrete effectiveness in one of the areas of most increasing concern, i.e., that of neurodegenerative diseases. PMID:18996199

Bertolini, Alfio; Tacchi, Raffaella; Vergoni, Anna Valeria

2009-01-01

413

ENVIRONMENTAL RESIDUE EFFECTS DATABASE (ERED)  

EPA Science Inventory

US Army Corps of Engineers public web site for the "Environmental Residue Effects Database", a searchable database of adverse biological effects associated with tissue concentrations of various contaminants....

414

Thermoelectric properties of n-type polycrystalline BixSb2-xTe3 alloys  

NASA Technical Reports Server (NTRS)

(BixSbl-x)2Te3(.5 = x = .7) polycrystalline samples were synthesized using a combination of melting and powder metallurgy techniques. The samples were hot pressed in graphite dies and cut perpendicular and parallel to the pressing direction. Samples were examined by microprobe analysis to determine their atomic composition. The thermoelectric properties were measured at room temperature in both directions. These properties include Seebeck coefficient, thermal conductivity, electrical resistivity, and Hall effect. The thermoelectric figure-of-merit, ZT, was calculated fiom these properties.

Snyder, J.; Gerovac, N.; Caillat, T.

2002-01-01

415

Electrical and electrothermal transport in InN: The roles of defects  

NASA Astrophysics Data System (ADS)

The transport properties of Mg doped and undoped InN films are studied with capacitance-voltage, thermopower, and Hall mobility measurements. A positive Seebeck coefficient is observed for Mg doped InN confirming p-type conductivity, though high doping and structural defect density can lead to n-type films. Transport measurements of undoped films are analyzed employing Rode's iterative Boltzmann equation method. Observed thermopower, Hall mobility, and dislocation density data for undoped films are consistent with calculations including the effects of charged line defect (donor-type dislocation) scattering.

Miller, N.; Ager, J. W.; Jones, R. E.; Smith, H. M.; Mayer, M. A.; Yu, K. M.; Hawkridge, M. E.; Liliental-Weber, Z.; Haller, E. E.; Walukiewicz, W.; Schaff, W. J.; Gallinat, C.; Koblmüller, G.; Speck, J. S.

2009-12-01

416

Thermoelectric Properties of P-doped Mg2Si Semiconductors  

Microsoft Academic Search

The thermoelectric properties of P-doped Mg2Si [Mg2Si:P=1:x (0.0005<=q x<=q 0.03)] fabricated by spark plasma sintering have been characterized by Hall effect measurements at 300 K and by measurements of electrical resistivity (rho), the Seebeck coefficient (S), and thermal conductivity (kappa) between 300 and 900 K. P-doped Mg2Si samples are n-type in the measured temperature range. The electron concentration of P-doped

Jun-ichi Tani; Hiroyasu Kido

2007-01-01

417

Microwave reflection imaging using a magnetic tunnel junction based spintronic microwave sensor  

NASA Astrophysics Data System (ADS)

A far-field microwave imaging technique has been developed using a spintronic sensor based on a magnetic tunnel junction (MTJ). Such a sensor can directly rectify a microwave field into a dc voltage signal using the Seebeck effect. Thanks to the high conversion efficiency of the microwave rectification in MTJs, the microwave power sensitivity of the spintronic sensor is on the order of 1-10 mV/mW. This high sensitivity allows the sensor to directly measure the coherent spatial scattered microwave field distribution, which gives it the ability to non-destructively detect hidden objects down to a few wavelengths in size.

Fu, L.; Cao, Z. X.; Hemour, S.; Wu, K.; Houssameddine, D.; Lu, W.; Pistorius, S.; Gui, Y. S.; Hu, C.-M.

2012-12-01

418

Thermoelectric properties of P-type antimony bismuth telluride alloys prepared by cold pressing  

SciTech Connect

Sb{sub 2{minus}x}Bi{sub x}Te{sub 3} (x = 0.43--0.51) thermoelectric materials were prepared by the powder metallurgy method. The effects of grinding and sintering processes on the Seebeck coefficient, electrical conductivity, and thermoelectric figure of merit were investigated. For different particle sizes, a shift in maximum of Z = f(x) dependence was found. This shift can be explained by the presence of point defects and their interaction. Cold-pressed material with Z {approximately} 3.1 {times} 10{sup {minus}3} K{sup {minus}1} was prepared.

Navratil, J.; Stary, Z.; Plechacek, T. [Academy of Sciences of the Czech Republic and Univ. of Pardubice (Czech Republic). Joint Lab. of Solid State Chemistry] [Academy of Sciences of the Czech Republic and Univ. of Pardubice (Czech Republic). Joint Lab. of Solid State Chemistry

1996-12-01

419

Transparent p-type conducting CuScO2+x films  

NASA Astrophysics Data System (ADS)

Transparent films of CuScO2+x have been prepared which show p-type electrical conductivity. The temperature dependence of the conductivity indicates semiconducting behavior with an apparent room temperature activation energy of 0.11 eV. The highest room temperature conductivity observed was 30 S cm-1. Films 110 nm thick show 40% transparency in most of the visible spectrum and become much more transparent in the infrared spectrum. The p-type behavior was confirmed by the Seebeck effect.

Duan, N.; Sleight, A. W.; Jayaraj, M. K.; Tate, J.

2000-08-01

420

Enhanced thermoelectric performance in p-type Ca 0.5Ce 0.5Fe 4? x Ni x Sb 12 skutterudites by adjusting the carrier concentration  

Microsoft Academic Search

Polycrystalline p-type Ca\\/Ce co-filled skutterudites Ca0.5Ce0.5Fe4?xNixSb12 (0?0?0.7) compounds have been successfully prepared by traditional melting-annealing-spark plasma sintering (SPS) method. The effective adjustment in carrier concentration dominates electronic transport behavior in a manner of significant decrease of electrical conductivity as well as the enhancement in Seebeck coefficient with increasing Ni-substitution, resulting in a slight degradation of power factor. Meanwhile, the thermal

Gangjian Tan; Shanyu Wang; Yonggao Yan; Han Li; Xinfeng Tang

421

Synthesis and electrical transport properties of p-type Ba8Ga16CdxGe30?x type-I clathrates  

Microsoft Academic Search

P-type Ba8Ga16CdxGe30-x (x=0.95, 1.00, 1.05, 1.10) type-I clathrates with different Cd contents were synthesized by combining melt method with spark plasma sintering (SPS). The effects of Cd content on electrical transport properties have been investigated. The results show that all samples exhibit p-type conduction. The Seebeck coefficient alpha and room temperature carrier mobility muH decrease with the increasing Cd content.

Shukang Deng; Xinfeng Tang; Han Li; Yonggao Yan; QingJie Zhang

2007-01-01

422

Polarons  

NASA Astrophysics Data System (ADS)

Preface; Acknowledgements; 1. Succinct overview; Part I. Polaron Formation: 2. Electron-phonon interactions; 3. Weak-coupling polarons: carrier-induced softening; 4. Strong-coupling: self-trapping; 5. Dopant- and defect-related small polarons; 6. Molecular polarons; 7. Bipolarons; 8. Magnetic polarons and colossal magneto-resistance; Part II. Polaron Properties: 9. Optical properties; 10. Large-polaron transport; 11. Small-polaron transport; 12. Polarons' Seebeck coefficients; 13. Polarons' Hall Effect; Part III. Extending Polaron Concept: 14. Superconductivity of large bipolarons; 15. Non-Ohmic hopping conduction and electronic switching; 16. Electronically stimulated desorption of atoms from surfaces; 17. Hopping of light atoms; References; Index.

Emin, David

2012-11-01

423

Latent effects decision analysis  

DOEpatents

Latent effects on a system are broken down into components ranging from those far removed in time from the system under study (latent) to those which closely effect changes in the system. Each component is provided with weighted inputs either by a user or from outputs of other components. A non-linear mathematical process known as `soft aggregation` is performed on the inputs to each component to provide information relating to the component. This information is combined in decreasing order of latency to the system to provide a quantifiable measure of an attribute of a system (e.g., safety) or to test hypotheses (e.g., for forensic deduction or decisions about various system design options).

Cooper, J. Arlin (Albuquerque, NM) [Albuquerque, NM; Werner, Paul W. (Albuquerque, NM) [Albuquerque, NM

2004-08-24

424

Doppler Effect Model  

NSDL National Science Digital Library

The Doppler Effect model demonstrates the shift in frequency of a wave that is produced by the motion of either the wave source or the observer of the wave (or both). In this simulation, you can explore the change in the wave that is produced by source and/or observer motion, and you can even view what the situation looks like from the perspective of the medium (the standard reference frame), the source, or the observer. The Doppler Effect model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_bu_Doppler.jar file will run the program if Java is installed.

Duffy, Andrew

2010-04-25

425

Nonequilibrium effects and baryogenesis  

SciTech Connect

Possible effects due to nonequilibrium dynamics in the Affleck-Dine mechanism of baryogenesis are examined. Using the closed-time-path formalism, the quantum fluctuation and the backreaction of the Affleck-Dine scalar field are incorporated self-consistently into the dynamical equations of the system by invoking a nonperturbative Hartree approximation. It is found that such nonequilibrium effects can significantly affect the amount of baryon asymmetry that can be generated. In particular, it is possible to generate the observed baryon asymmetry with suitable initial conditions. The methodology described in this paper as well as some of the results obtained are quite general, and can be applied to any complex scalar field in a cosmological background.

Charng, Y.-Y.; Ng, K.-W. [Institute of Physics, Academia Sinica, Taipei, Taiwan 115 (China); Lee, D.-S. [Department of Physics, National Dong Hwa University, Hua-Lien, Taiwan 974 (China); Theory Group, Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom); Leung, C.N. [Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716 (United States)

2005-12-15

426

Postantifungal effect methods.  

PubMed

Postantifungal effect (PAFE) is the evaluation of antifungal activity after the suppression of fungal growth when the drug is removed from the fungal suspension. In vitro, this effect might simulate the in vivo situation when the concentration of the drug falls to less than the minimum inhibitory concentration values and could be another tool, together with the classic in vitro susceptibility tests, to optimize the interaction of drugs-fungi. In this chapter, two model methods to evaluate the PAFE of yeasts and filamentous fungi are described in which practical advices and tricks are given to help the worker to develop the techniques. The procedures outlined include preparation of stock solutions of the drugs, concentration medium, exposure time colony count determination, and interpretation of the results to quantify the PAFE. PMID:15888941

Vitale, Roxana G

2005-01-01

427

The Energy Diameter Effect  

NASA Astrophysics Data System (ADS)

We explore various relations for the detonation energy and velocity as they relate to the inverse radius of the cylinder. The effective detonation rate-inverse slope relation seen in reactive flow models can be used to derive the familiar Eyring equation. Generalized inverse radii can be shown to fit large quantities of cylinder results. A rough relation between detonation energy and detonation velocity is found from collected JWL values. Cylinder test data for ammonium nitrate mixes down to 6.35 mm radii are presented, and a size energy effect is shown to exist in the Cylinder test data. The relation that detonation energy is roughly proportional to the square of the detonation velocity is shown by data and calculation.

Vitello, Peter; Garza, Raul; Hernandez, Andy; Souers, P. Clark

2007-12-01

428

[Herbs and cardiotoxic effects].  

PubMed

Accidental or deliberate ingestion of poisonous herbs has become an increasingly common phenomenon over the last years. From existing literature data and case reports from emergency room visits or poison control centers, an overview is presented of the potential cardiotoxic manifestations following intoxication by wild herbal plants of the territory. The effects of the consumption of cardiac glycoside-containing plants (e.g., digitalis) are discussed along with tachyarrhythmias induced by Aconitum napellus L., Atropa belladonna L., Mandragora officinarum L. or Ephedra distachya L. herbs, and hypertensive crises associated with licorice abuse. For each plant, a brief historical and botanical background is provided, focusing on pathophysiology of intoxication and cardiotoxic effects on the basis of the most recent literature. Finally, medical management of intoxication, from both a general and cardiological viewpoint, is reviewed. PMID:23748541

Maffè, Stefano; Paffoni, Paola; Laura Colombo, Maria; Davanzo, Franca; Dellavesa, Pierfranco; Cucchi, Lorenzo; Zenone, Franco; Paino, Anna Maria; Franchetti Pardo, Nicolò; Bergamasco, Luca; Signorotti, Fabiana; Parravicini, Umberto

2013-06-01

429

Fire Effects Information System  

NSDL National Science Digital Library

The Fire Effects Information System (FEIS) provides up-to-date information about fire effects on plants and animals. It was developed at the USDA Forest Service Rocky Mountain Research Station's Fire Sciences Laboratory in Missoula, Montana. The FEIS database contains synoptic descriptions, taken from current English-language literature of almost 900 plant species, about 100 animal species, and 16 Kuchler plant communities found on the North American continent. The emphasis of each synopsis is fire and how it affects each species. Background information on taxonomy, distribution, basic biology and ecology of each species is also included. Synopses are thoroughly documented, and each contains a complete bibliography. Personnel from several land management agencies (USDA Forest Service, USDI-BIA, NPS, BLM, F&WS) identified the species to be included in the database. Those agencies funded the original work and continue to support maintenance and updating of the database.

1995-12-12

430

Effective Vaccination Policies  

PubMed Central

We present a framework for modeling the spread of pathogens throughout a population and generating policies that minimize the impact of those pathogens on the population. This framework is used to study the spread of human viruses between cities via airplane travel. It combines agent-based simulation, mathematical analysis, and an Evolutionary Algorithm (EA) optimizer. The goal of this study is to develop tools that determine the optimal distribution of a vaccine supply in the model. Using plausible benchmark vaccine allocation policies of uniform and proportional distribution, we compared their effectiveness to policies found by the EA. We then designed and tested a new, more effective policy which increased the importance of vaccinating smaller cities that are flown to more often. This “importance factor” was validated using U.S. influenza data from the last four years.

Shaw, L.; Spears, W.; Billings, L.; Maxim, P.

2010-01-01

431

Cardiac effects of thyronamines.  

PubMed

3-Iodothyronamine (T(1)AM) is an endogenous compound derived from thyroid hormone through decarboxylation and deiodination, which interacts with a novel G protein-coupled receptor, known as trace amine-associated receptor 1 (TAAR1). TAAR1 and other receptors of this family are expressed in several tissues, including the heart. Functional effects have been observed after administration of exogenous T(1)AM: in the isolated heart, a negative inotropic and chronotropic action was produced, and the resistance to ischemic injury was increased, possibly as a consequence of an action on intracellular calcium homeostasis. Extracardiac effects include reduction of body temperature, increased lipid versus carbohydrate metabolism, and modulation of insulin secretion. T(1)AM might play an important physiological or pathophysiological role, and this signaling system might allow the development of new therapeutical agents. PMID:19016324

Zucchi, Riccardo; Ghelardoni, Sandra; Chiellini, Grazia

2010-03-01

432

The Dufour effect  

Microsoft Academic Search

Equations for the Dufour effect, which is the development of a temperature gradient due to diffusion, have been solved for geometrically well-defined cells which have either all walls adiabatic or adiabatic lateral walls and diathermic ends. Two self-consistent, well-ordered perturbation schemes have been used, and heat of mixing, variability of all properties, and the barycentric velocity are included explicitly. For

Sara E. Ingle; Frederick H. Horne

1973-01-01

433

Power electronics' polluting effects  

Microsoft Academic Search

In use far and wide for improved delivery and control of the electricity supply, power electronics systems are both the cause and remedy of the power system harmonic pollution problem. Here, the authors describe how an insidious side-effect of any solution involving power electronics converters is their generation of high-frequency pollution-namely, conducted and radiated noise in the 100 kHz to

R. Redl; P. Tenti; J. Daan van Wyk

1997-01-01

434

The Kaye effect  

NASA Astrophysics Data System (ADS)

The International Young Physicists' Tournament (IYPT) is a worldwide, annual competition for secondary school students. This is our solution to problem number 10, The Kaye effect, as presented in the final round of the 21st IYPT in Trogir, Croatia. The Kaye effect occurs when a thin stream of shampoo or a different adequate non-Newtonian liquid is poured onto a surface. Suddenly, a jet leaves the heap that is formed by the shampoo and begins to 'dance' around the primary jet like a lasso. The phenomenon ends when the 'dancing' jet hits the primary jet and subsequently collapses. We started our investigations based on available literature (Kaye 1963 Nature 197 1001, Versluis et al 2006 J. Stat. Mech., Collyer and Fischer 1976 Nature 261 682). We made experiments with a similar experimental set-up in which we could determine the velocities of both shampoo streams as well as the angle of the 'dancing' stream. From there on, we developed a theoretical model for the energy loss of the jet in the heap. We discovered that the air layer between the jet and the heap is a necessity for the Kaye effect to occur. At this point, our observations differ from the aforementioned literature. This also accounts for the shampoo beam acting as a light guide. Further experiments concerning the viscoelasticity of the shampoo revealed that the elastic property of the shampoo is necessary for the effect to occur. This article is a written version of the oral contribution of the German team to the 21st IYPT competition, which was awarded first prize by an international jury. The article has been edited by European Journal of Physics.

Binder, J. M.; Landig, A. J.

2009-11-01

435

Temporary Retinal Effects  

Microsoft Academic Search

IN your present week's ``Notes'' you have referred to the curious experiences of MM. Macé de Lepinay and Nicati, in finding the town lights appear green, after five hours among snow-fields. On the Cima di Jazi, some 16,000 feet or more high, I found another effect. On removing my blue snow-glasses, the sky (at about 10 a.m.) appeared of the

J. Rand Capron

1882-01-01

436

SGEMP Geometry Effects  

Microsoft Academic Search

Self-consistent, fully dynamic computer calculations were performed using the recently developed arbitrary body-of-revolution code ABORC for complex geometries in SGEMP environments to test the validity of simplifying geometry assumptions previously made in the solutions of these problems. Assumptions such as simple geometry representations of complex bodies and separability of inside and outside problems are tested. Effects of gaps, interior electrical

A. J. Woods; E. P. Wenaas

1975-01-01

437

The Effects of Outliers  

NSDL National Science Digital Library

Created by Illuminations: Resources for Teaching Mathematics, this lesson is designed to help students understand the significance of outliers. This lesson includes thought questions and an applet to help students visualize the effect of an outlier. The authors divide the lesson into different groups, they include: learning objectives, materials, instructional plans, NCTM standards/expectations, and finally references. This is a great interactive resource for those wanting to learn more about correlation and regression.

2009-01-01

438

Writing Effective TAFs  

NSDL National Science Digital Library

This module provides an overview of some of the applicable TAF Amendment and Conditional Group usage rules, as presented in the latest version of the National Weather Service Instruction 10-813 on TAF directives. It also presents a methodology for TAF writing and development that will lead to an effective and user-friendly product. The focus is on the ceiling and visibility aspects of the TAF. This module is part of the Distance Learning Course 1: Forecasting Fog and Low Stratus

Spangler, Tim

2003-06-28

439

Extra Housepayments Effect  

NSDL National Science Digital Library

How financial institutions use the monthly mortgage payment and mortgage amortization formulas can be a confusing concept to grasp. This lesson asks students to find a current interest mortgage rate for their city and state. This rate is then applied to an Internet based mortgage calculator to discover the effect that paying extra on a monthly house payment has on total interest paid and length of the loan. A student worksheet is included in the document.

2011-01-05

440

Electromechanical Effects in  

Microsoft Academic Search

Electric fields Can induce mechanical vibratiam in plattar aligned sandwich cells of ferroelectric liquid crystals. L.Measurements on a polysiloxane and a polyacy~aie side chain polymer proved that the rlectromechanical effect also exists in frrroelcctric liquid cystallinc polymers. fie main characteristics of the eiectromed~anical res- ponses of fhese polymers are described and compared to the response of low molecu2ur weight fcrroelectric

Ferroelectric Liquid; Crystalline Polymers; Antal Jbklit; Laios Bafa

441

Transgenerational Effects of NMs.  

PubMed

Nanomaterials are present in a number of commercially available products but there are uncertainties as to whether the unique properties that support their commercial use may also pose potential health risks. Information is missing concerning the influence of nanomaterials on the overall reproductive outcome and transgenerational effects in animals and plants. To obtain this information, long-term studies would be required using animal models phylogenetically close to humans and exposure conditions that reflect realistic scenarios with regard to dosages and admission. The nanoreprotoxicology literature published to date is largely descriptive in nature regarding the effects of nanoparticles. The mechanisms, which determine particle reproduction compatibility, are mostly elusive at the moment. Thus, it is recommended that future research explore the interactions between nanomaterials and transgenerational matter on a molecular level. It would, for instance, be of major importance to understand the behaviour of nanoparticles inside the cells but also their genotoxic and epigenetic effects. Recent studies have shown that intravenous and/or intra-abdominal administration of nanoparticles to mice results in their accumulation in the cells of many tissues, including the brain and the testis, suggesting that they easily pass through the blood-brain and blood-testis barriers. In parallel embryo development after exposure to nanoparticles should be comparatively investigated. The majority of studies on embryo toxicology have concentrated on piscine embryos, mostly derived from zebrafish. Plants for human food as an important component of the ecosystem need also to be taken into account when evaluating transgenerational effects of engineered nanomaterials in crops. PMID:24683035

Poma, Anna; Colafarina, Sabrina; Fontecchio, Gabriella; Chichiriccò, Giuseppe

2014-01-01

442

Neuroprotective effects of creatine  

Microsoft Academic Search

There is a substantial body of literature, which has demonstrated that creatine has neuroprotective effects both in vitro\\u000a and in vivo. Creatine can protect against excitotoxicity as well as against ?-amyloid toxicity in vitro. We carried out studies\\u000a examining the efficacy of creatine as a neuroprotective agent in vivo. We demonstrated that creatine can protect against excitotoxic\\u000a lesions produced by

M. Flint Beal

2011-01-01

443

Lightning effects on aircraft  

NASA Technical Reports Server (NTRS)

Direct and indirect effects of lightning on aircraft were examined in relation to aircraft design. Specific trends in design leading to more frequent lightning strikes were individually investigated. These trends included the increasing use of miniaturized, solid state components in aircraft electronics and electric power systems. A second trend studied was the increasing use of reinforced plastics and other nonconducting materials in place of aluminum skins, a practice that reduces the electromagnetic shielding furnished by a conductive skin.

1977-01-01

444

Tasting edge effects  

NASA Astrophysics Data System (ADS)

We show that the baking of potato wedges constitutes a crunchy example of edge effects, which are usually demonstrated in electrostatics. A simple model of the diffusive transport of water vapor around the potato wedges shows that the water vapor flux diverges at the sharp edges in analogy with its electrostatic counterpart. This increased evaporation at the edges leads to the crispy taste of these parts of the potatoes.

Bocquet, Lydéric

2007-02-01

445

Electromagnetic environmental effects compendium  

NASA Astrophysics Data System (ADS)

This report summarizes the electromagnetic environmental effects (E3) program of the U.S. Army Communications-Electronics Command (CECOM). The report includes background information on CECOM's role in the Army E3 program, presents the approach used to identify the electromagnetic environment, summarizes E3 criteria (i.e., the CECOM model electromagnetic environment), and provides a sample E3 assessment. The report also discusses electromagnetic trends and their implications.

Brockel, Kenneth H.; Cofield, David; Deallaume, William; Gorr, Lanny; Major, Paul A.

1993-08-01

446

Quantum effects in biology  

Microsoft Academic Search

The idea that quantum-mechanical phenomena can play nontrivial roles in biology has fascinated researchers for a century. Here we review some examples of such effects, including light-harvesting in photosynthesis, vision, electron- and proton-tunneling, olfactory sensing, and magnetoreception. We examine how experimental tests have aided this field in recent years and discuss the importance of developing new experimental probes for future

Graham R. Fleming; Gregory D. Scholes; Yuan-Chung Cheng

2011-01-01

447

Cost-Effectiveness Analyses  

Microsoft Academic Search

Surgical research has traditionally focused on comparing health outcome measures of a new technique with accepted practice.\\u000a As health care resources become scarcer and options for newer, more expensive diagnostic tests and surgical interventions\\u000a increase, incorporating cost-effectiveness analysis (CEA) into surgical research studies becomes increasingly important. CEA\\u000a provides the information necessary to allow resource allocation decisions to be based on

Lynn Stothers

448

Low-Temperature Drift in MIMS Base-Metal Thermocouples  

NASA Astrophysics Data System (ADS)

Inhomogeneities are known to develop within thermoelements exposed to elevated temperatures, resulting in temperature measurement errors. While the Seebeck coefficient drift in base-metal thermocouples due to aging at temperatures over 200° C has been extensively investigated, there have been very few investigations into possible Seebeck changes at lower temperatures. Despite warnings about possible effects, most practitioners assume changes in homogeneity are either not significant or not able to develop at temperatures less than 200° C . This study reports on measurements of inhomogeneities in base-metal thermocouples arising from heat treatment at temperatures in the region of 200° C . Thermoelectric scans of thermocouples were carried out following exposure of a range of mineral-insulated metal-sheathed base-metal thermocouples, from two large manufacturers, of Types E, J, K, N, and T, to either a linear-gradient furnace within the range of 100° C to 320° C or uniform temperature zones of 100° C , 150° C , and 200° C . The experiments reveal noticeable drift in all base-metal types for temperatures as low as 100° C and exposure times as short as 1 h. The most sensitive thermoelement alloys appear to be Constantan, Alumel, and Nicrosil. It is concluded that the common working assumption that base-metal thermocouples suffer no thermally induced changes in the Seebeck coefficient below 200° C is false. This observation has significant implications for many high-stability monitoring and control systems reliant on base-metal thermocouples that operate in the range of 100° C to 200° C . Additionally, thermoelectric scanning of base-metal thermocouples should be carried out at temperatures well below 150° C to avoid erasure of strain effects or imprinting of new thermal signatures.

Webster, E. S.

2014-03-01

449

Ejs Doppler Effect Model  

NSDL National Science Digital Library

The Ejs Doppler Effect model displays the detection of sound waves from a moving source and the change in frequency of the detected wave via the Doppler effect. In addition to the wave fronts from the source a graph depicting the time of emission and time of detection of each of the wave fronts is given. The speed of sound, the velocity of the source and the position and velocity of the detector can be changed via text boxes. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. Ejs Doppler Effect model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_ehu_waves_doppler.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models for wave optics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Aguirregabiria, Juan

2008-08-20

450

Effective properties of metamaterials  

NASA Astrophysics Data System (ADS)

Properties of metamaterials are usually discussed in terms of biaxial anisotropic material parameters. To consider the underlying constitutive relations as valid, it is required that only weak spatial dispersion occurs. At operational frequencies of optical metamaterials this assumption often ceases to be valid. A description using effective material properties tends to be inadequate and new approaches are required. We outline here our latest achievements along this direction and discuss two approaches. The first one assumes that if it is not possible to introduce useful effective properties, a more primary source of information should be used to quantify metamaterials, leading to a characterization of metamaterials in terms of Jones matrices. We discuss the implications of this description and show that all metamaterials can be categorized into five classes, each with distinct properties. The second approach resorts to an effective description but restricts its considerations to a dispersion relation, characterizing the propagation of light in bulk metamaterials, and an impedance, characterizing the coupling between metamaterials and their surroundings. Definitions of both properties linked to a single Bloch mode are discussed and metamaterials are introduced which can be homogenized while considering only this single mode.

Rockstuhl, C.; Menzel, C.; Paul, T.; Pshenay-Severin, E.; Falkner, M.; Helgert, C.; Chipouline, A.; Pertsch, T.; ?migaj, W.; Yang, J.; Lalanne, P.; Lederer, F.

2011-09-01

451

Planetary Electrochemical Effects  

NASA Astrophysics Data System (ADS)

Lightning on a planet other than the Earth was first discovered by Voyager when it flew past Jupiter in 1979. Since then it has been reported on Saturn by Voyager and Cassini, and on Venus from Pioneer Venus and Venus Express. While lightning involves clouds formed from polar molecules such as water, or vulcanism, dusty environments often create electrostatic fields through triboelectric phenomena. In each instance, changes in local chemistry with profound global impact can occur, such as lightning-induced nitrogen fixation on earth. Perhaps the most dramatic effect occurs on Mars within its global dust storms and dust devils. Enhanced production of oxidants, such as hydrogen peroxide, sulfur and halogen species including perhaps perchlorates from minerals in airborne dust are some of the likely chemical effects. The oxidants may be responsible for the lack of organics on the surface of Mars and rapid destruction of methane in the atmosphere. On Titan, the surface organics may be altered by a different (charged particle) effect, a phenomena that may also operate in the polar regions of Mars and on the Galilean satellites. In this talk, we will discuss possible chemical and astrobiological implications of above electrical processes.

Atreya, S. K.; Mihalka, K. M.; Mahaffy, P. R.; Delory, G. T.; Farrell, W. M.

2008-12-01

452

Photoelectric Effect Model  

NSDL National Science Digital Library

The EJS Photoelectric Effect model simulates the Photoelectric effect discovered by Hertz in 1887 and described theoretically by Einstein in 1905. Light of a given frequency (energy) shines on a metal in a vacuum tube. If the energy of the photons is greater than the work function of the metal, W, electrons are ejected and can form a current in an external circuit. These photoelectrons will have a kinetic energy if the energy of the light is greater than the work function. If subjected to an electric potential between the plates in the tube, the electrons excited from the metal will be accelerated resulting in an increase, decrease, or stopping of the current. This model provides controls for the frequency of the light source and the external potential on the electron tube. An ammeter allows users to take data for the photo-current. The EJS Photoelectric Effect model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_qm_photoelectric.jar file will run the program if Java is installed.

Palop, Jose I.

2010-07-16

453

Metabolic effects of alcohol.  

PubMed

The metabolic effects of ethanol are due to a direct action of ethanol or its metabolites, changes in the redox state occurring during its metabolism, and modifications of the effects of ethanol by nutritional factors. Ethanol causes hyperglycemia or hypoglycemia depending on whether glycogen stores are adequate, inhibits protein synthesis, and results in fatty liver and in elevations in serum triglyceride levels. Increases in high-density lipoprotein cholesterol after ethanol ingestion may explain the lower risk of myocardial infarction and death from coronary disease after moderate drinking. Increases in serum lactate, resulting from the increased NADH/NAD+ ratio, and hyperuricemia, most likely the result of increased turnover of adenine nucleotides, are common transient effects of ethanol ingestion. Causes of vitamin deficiencies in alcoholism are decreased dietary intake, decreased intestinal absorption, and alterations in vitamin metabolism. Ethanol decreases thiamine absorption and decreases the enterohepatic circulation of folate. Acetaldehyde increases the degradation of pyridoxal 5'-phosphate by displacing it from its binding protein and making it susceptible to hydrolysis by membrane-bound alkaline phosphatase. Ethanol decreases hepatic vitamin A concentration and its conversion to active retinal, and modifies renal metabolism of vitamin D. PMID:3881285

Mezey, E

1985-01-01

454

Calculating and Synthesizing Effect Sizes  

Microsoft Academic Search

The effect size is a standardized, scale-free measure of the relative size of the effect of an interven- tion, and it has important and practical implications for clinicians in the speech and hearing field who are interested in estimating the effects of interventions. This article develops a conceptual interpretation of the effect size, makes explicit assumptions for its proper use

Herbert M. Turner; Robert M. Bernard

2006-01-01

455

Evolution of Earth's Greenhouse Effect  

Microsoft Academic Search

The major factors contributing to Earth's greenhouse effect are discussed along with various quantitative methods for determining the greenhouse effect. Earth's greenhouse effect has evolved over geologic time scales and continues to evolve. The magnitude of Earth's greenhouse effect is explored for particular time periods of Earth's evolution from the Neoproterozoic to present. Coupled climate model simulations for these various

J. T. Kiehl

2003-01-01

456

SOLAR EFFECTS ON BUILDING DESIGN.  

ERIC Educational Resources Information Center

A REPORT OF A PROGRAM HELD AS PART OF THE BUILDING RESEARCH INSTITUTE 1962 SPRING CONFERENCE ON THE SOLAR EFFECTS ON BUILDING DESIGN. TOPICS DISCUSSED ARE--(1) SOLAR ENERGY DATA APPLICABLE TO BUILDING DESIGN, (2) THERMAL EFFECTS OF SOLAR RADIATION ON MAN, (3) SOLAR EFFECTS ON ARCHITECTURE, (4) SOLAR EFFECTS ON BUILDING COSTS, (5) SELECTION OF…

Building Research Inst., Inc., Washington, DC.

457

Computational study of energy filtering effects in one-dimensional composite nano-structures  

NASA Astrophysics Data System (ADS)

Possibilities to improve the Seebeck coefficient S versus electrical conductance G trade-off of diffusive composite nano-structures are explored using an electro-thermal simulation framework based on the non-equilibrium Green's function method for quantum electron transport and the lattice heat diffusion equation. We examine the role of the grain size d, potential barrier height ?B, grain doping, and the lattice thermal conductivity ?L using a one-dimensional model structure. For a uniform ?L, simulation results show that the power factor of a composite structure may be improved over bulk with the optimum ?B being about kBT, where kB and T are the Boltzmann constant and the temperature, respectively. An optimum ?B occurs because the current flow near the Fermi level is not obstructed too much while S still improves due to barriers. The optimum grain size dopt is significantly longer than the momentum relaxation length ?p so that G is not seriously degraded due to the barriers, and dopt is comparable to or somewhat larger than the energy relaxation length ?E so that the carrier energy is not fully relaxed within the grain and |S| remains high. Simulation results also show that if ?L in the barrier region is smaller than in the grain, S and power factor are further improved. In such cases, the optimum ?B and dopt increase, and the power factor may improve even for ?B (d) significantly higher (longer) than kBT (?E). We find that the results from this quantum mechanical approach are readily understood using a simple, semi-classical model.

Kim, Raseong; Lundstrom, Mark S.

2012-01-01

458

Verbal response-effect compatibility  

Microsoft Academic Search

Ideomotor theory states that motor responses are activated by an anticipation of their sensory effects. We assumed that anticipated\\u000a effects would produce response-effect (R-E) compatibility when there is dimensional overlap of effects and responses. In a\\u000a four-choice task, visual digit stimuli called for verbal responses (color names). Each response produced a written response-effect\\u000a on the screen. In different groups, the

Iring Koch; Wilfried Kunde

2002-01-01

459

40 CFR 1508.8 - Effects.  

Code of Federal Regulations, 2013 CFR

...Effects. Effects include: (a) Direct effects, which are caused by the...foreseeable. Indirect effects may include growth inducing effects and other effects...economic, social, or health, whether direct, indirect, or cumulative....

2013-07-01

460

``The Kesterson effect''  

NASA Astrophysics Data System (ADS)

Hypothesized to be derived from Cretaceous marine sedimentary rocks, selenium contamination of the Kesterson National Wildlife Refuge is traced through irrigation drainage to the source bedrock of the California Coast Ranges. This biogeochemical pathway of selenium is defined here as the “Kesterson effect.” At the refuge ponds, this effect culminated in 1983 in a 64% rate of deformity and death of embryos and hatchlings of wild aquatic birds. From the previous companion paper on irrigation drainage, the Kesterson effect has been implicated in nine of 11 reconnaissance areas studied in the western United States. Deformities have resulted in at least five of these sites. Climatic, geologic, hydrologic, and soil conditions in these reconnaissance areas are similar to those in the area surrounding Kesterson National Wildlife Refuge in the west-central San Joaquin Valley of California. In California, selenium, as selenate, was ultimately found weathered with sulfur from marine sources in soluble sodium and magnesium sulfate salts, which are concentrated by evaporation on farmland soils. The Se, mobilized by irrigation drainage, is bioaccumulated to toxic levels in refuge wetland ponds that are located mainly in hydrologically closed basins and thus act as concentrating disposal points. The depositional environment of the ponds may be similar to that of the nutrient-rich continental shelf edge and slope in which Cretaceous, Eocene, and Miocene sediments found to be seleniferous in the California Coast Ranges were deposited. Bioaccumulation may be therefore a primary mechanism of selenium enrichment in ancient sediments in addition to that of the formerly suggested Cretaceous volcanic pathway.

Presser, Theresa S.

1994-05-01

461

Effective Gauge Theory  

NASA Astrophysics Data System (ADS)

The global iso-spin invariance of the hadronic interaction, which is areflection of the SU(2) × U(1) QFD and QCD, as well as the U(1) invariance related to the charge of the hadrons, is formulated as an effective gauge theory. The pseudo-gauge fields in this theory are the vector mesons, and these composite fields become massive when the Higgs field at the quark-lepton level and the bar{q}q pair states acquire the vacuum expectation value. The formulation gives a theoretical basis for the vector dominance model and gives some insights to the possible composite structure of quarks and leptons.

Ebata, T.

1982-02-01

462

Photochemical Effects of Sunlight  

PubMed Central

The importance of sunlight in bringing about not only photosynthesis in plants, but also other photochemical effects, is reviewed. More effort should be devoted to photochemical storage of the sun's energy without the living plant. There is no theoretical reason to believe that such reactions are impossible. Ground rules for searching for suitable solar photochemical reactions are given, and a few attempts are described, but nothing successful has yet been found. Future possibilities are suggested. Photogalvanic cells which convert sunlight into electricity deserve further research. Eugene Rabinowitch has been an active pioneer in these fields.

Daniels, Farrington

1972-01-01

463

Radiative Effects of Aerosols  

NASA Technical Reports Server (NTRS)

During the Atlantic Stratocumulus Transition Experiment (ASTEX) in June 1992, two descents in cloud-free regions allowed comparison of the change in aerosol optical depth as determined by an onboard total-direct-diffuse radiometer (TDDR) to the change calculated from measured size resolved aerosol microphysics and chemistry. Both profiles included pollution haze layer from Europe but the second also included the effect of a Saharan dust layer above the haze. The separate contributions of supermicrometer (coarse) and submicrometer (fine) aerosol were determined and thermal analysis of the pollution haze indicated that the fine aerosol was composed primarily of a sulfate/water mixture with a refractory soot-like core.

Valero, Francisco P. J.

1997-01-01

464

Effect of "terminal explosion"  

NASA Astrophysics Data System (ADS)

We consider the entry into the Earth's atmosphere of a cosmic body at hypersonic speeds. Large aerodynamic charges, the forces of inertia, and heat flow to the body surface lead to mass loss or even destruction of the body. The movement of the fragment cloud caused by the destruction of the body is a separate problem. From observations, we know that the flight of a cosmic body often ends with a terminal flare. We present one possible estimate of the energy in the final stages of the destruction of the body, confirming the possibility of the observed effect of the "terminal explosion" of the meteoroid.

Egorova, L.

2012-01-01

465

Butterfly Effect Fractal  

NASA Astrophysics Data System (ADS)

In this paper, a new concept of integration of fractal and the butterfly effect is proposed and implemented. A new fractal program was designed and developed to perform such integration. Among many existing fractal and chaos software programs, none of them allow us to achieve the resulting patterns demonstrated in this paper. Moreover, it is the first time that a fractal program provides functional concepts of overlapping results in 3D space and sequential transformations, which allow us to generate a wider variety of patterns. Therefore, potentially an artist can use this program to create 2D digital artworks.

Chang, Yin-Wei; Huang, Fay