Bismuth chalcohalides and oxyhalides as optoelectronic materials

DOE PAGES

Du, Mao -Hua; Shi, Hongliang; Ming, Wenmei

2016-03-29

Several Tl and Pb based halides and chalcohalides have recently been discovered as promising optoelectronic materials [i.e., photovoltaic (PV) and gamma-ray detection materials]. Efficient carrier transport in these materials is attributed partly to the special chemistry of ns 2 ions (e.g., Tl +, Pb 2+, and Bi 3+). However, the toxicity of Tl and Pb is challenging to the development and the wide use of Tl and Pb based materials. In this paper, we investigate materials that contain Bi 3+, which is also an ns 2 ion. By combining Bi halides with Bi chalcogenides or oxides, the resulting ternary compoundsmore » exhibit a wide range of band gaps, offering opportunities in various optoelectronic applications. Density functional calculations of electronic structure, dielectric properties, optical properties, and defect properties are performed on selected Bi 3+ based chalcohalides and oxyhalides, i.e., BiSeBr, BiSI, BiSeI, and BiOBr. We propose different applications for these Bi compounds based on calculated properties, i.e., n-BiSeBr, p-BiSI, and p-BiSeI as PV materials, BiSeBr and BiSI as room-temperature radiation detection materials, and BiOBr as a p-type transparent conducting material. BiSeBr, BiSI, and BiSeBr have chain structures while BiOBr has a layered structure. However, in BiSI, BiSeI, and BiOBr, significant valence-band dispersion is found in the directions perpendicular to the atomic chain or layer because the valence-band edge states are dominated by the halogen states that have strong interchain or interlayer coupling. We find significantly enhanced Born effective charges and anomalously large static dielectric constants of the Bi compounds, which should reduce carrier scattering and trapping and promote efficient carrier transport in these materials. The strong screening and the small anion coordination numbers in Bi chalcohalides should lead to weak potentials for electron localization at anion vacancies. As a result, defect calculations indeed show that the anion vacancies (Se and Br vacancies) in BiSeBr are shallow, which is beneficial to efficient electron transport.« less

Electronic conductivity studies on oxyhalide glasses containing TMO

NASA Astrophysics Data System (ADS)

Vijayatha, D.; Viswanatha, R.; Sujatha, B.; Narayana Reddy, C.

2016-05-01

Microwave-assisted synthesis is cleaner, more economical and much faster than conventional methods. The development of new routes for the synthesis of solid materials is an integral part of material science and technology. The electronic conductivity studies on xPbCl2 - 60 PbO - (40-x) V2O5 (1 ≥ x ≤ 10) glass system has been carried out over a wide range of composition and temperature (300 K to 423 K). X-ray diffraction study confirms the amorphous nature of the samples. The Scanning electron microscopic studies reveal the formation of cluster like morphology in PbCl2 containing glasses. The d.c conductivity exhibits Arrhenius behaviour and increases with V2O5 concentration. Analysis of the results is interpreted in view Austin-Mott's small polaron model of electron transport. Activation energies calculated using regression analysis exhibit composition dependent trend and the variation is explained in view of the structure of lead-vanadate glass.

Expanding frontiers in materials chemistry and physics with multiple anions.

PubMed

Kageyama, Hiroshi; Hayashi, Katsuro; Maeda, Kazuhiko; Attfield, J Paul; Hiroi, Zenji; Rondinelli, James M; Poeppelmeier, Kenneth R

2018-02-22

During the last century, inorganic oxide compounds laid foundations for materials synthesis, characterization, and technology translation by adding new functions into devices previously dominated by main-group element semiconductor compounds. Today, compounds with multiple anions beyond the single-oxide ion, such as oxyhalides and oxyhydrides, offer a new materials platform from which superior functionality may arise. Here we review the recent progress, status, and future prospects and challenges facing the development and deployment of mixed-anion compounds, focusing mainly on oxide-derived materials. We devote attention to the crucial roles that multiple anions play during synthesis, characterization, and in the physical properties of these materials. We discuss the opportunities enabled by recent advances in synthetic approaches for design of both local and overall structure, state-of-the-art characterization techniques to distinguish unique structural and chemical states, and chemical/physical properties emerging from the synergy of multiple anions for catalysis, energy conversion, and electronic materials.

Synthesis of belt-like BiOBr hierarchical nanostructure with high photocatalytic performance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Haiping; Liu, Jingyi; Hu, Tingxia

2016-05-15

Highlights: • BiOBr hierarchical nanobelts (NBs) were solvothermally prepared. • NBs show higher specific surface area and photoabsorption than BiOBr nanosheets. • NBs exhibit higher photoactivity than the nanosheets. - Abstract: One-dimensional (1D) bismuth oxyhalide (BiOX) hierarchical nanostructures are always difficult to prepare. Herein, we report, for the first time, a simple synthesis of BiOBr nanobelts (NBs) via a facile solvothermal route, using bismuth subsalicylate as the template and bismuth source. The BiOBr nanobelts are composed of irregular single crystal nanoparticles with highly exposed (0 1 0) facets. Compared with the BiOBr nanosheets (NSs) with dominant exposed (0 0 1)more » facets, they exhibit higher photocatalytic activity toward degradation of Rhodamine B and Methylene Blue under visible light irradiation. The higher photocatalytic performance of BiOBr NBs arises from their larger specific surface area and higher photoabsorption capability. This study provides a simple route for synthesis of belt-like Bi-based hierarchical nanostructures.« less

Electronic conductivity studies on oxyhalide glasses containing TMO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vijayatha, D.; Department of Physics, Gurunanak Institute of Technology, Hyderabad -040; Viswanatha, R.

2016-05-06

Microwave-assisted synthesis is cleaner, more economical and much faster than conventional methods. The development of new routes for the synthesis of solid materials is an integral part of material science and technology. The electronic conductivity studies on xPbCl{sub 2} – 60 PbO – (40-x) V{sub 2}O{sub 5} (1 ≥ x ≤ 10) glass system has been carried out over a wide range of composition and temperature (300 K to 423 K). X-ray diffraction study confirms the amorphous nature of the samples. The Scanning electron microscopic studies reveal the formation of cluster like morphology in PbCl{sub 2} containing glasses. The d.c conductivity exhibitsmore » Arrhenius behaviour and increases with V{sub 2}O{sub 5} concentration. Analysis of the results is interpreted in view Austin-Mott’s small polaron model of electron transport. Activation energies calculated using regression analysis exhibit composition dependent trend and the variation is explained in view of the structure of lead-vanadate glass.« less

Polyethylene imine-grafted ACF@BiOI0.5Cl0.5 as a recyclable photocatalyst for high-efficient dye removal by adsorption-combined degradation

NASA Astrophysics Data System (ADS)

Li, Hongyan; Li, Najun; Chen, Dongyun; Xu, Qingfeng; Lu, Jianmei

2017-05-01

A recyclable photocatalyst with adsorption property was prepared for high-efficient complete removal of anionic dyes from water by synergetic adsorption and photocatalytic degradation. Firstly, binary bismuth oxyhalide composed as BiOI0.5Cl0.5 was immobilized on activated carbon fibers (ACF) to get a recyclable photocatalyst (ACF@BiOI0.5Cl0.5) via one-step solvothermal method. Then it was modified with branched polyethylene imine (PEI) whose abundant amino groups can adsorb contaminants from water by electrostatic interaction. SEM images showed that the nanosheets-based flower-like photocatalytic microspheres uniformly distributed on the ACF surface after grafting of small amount of PEI. But from TGA results we can deduce that the percentage of PEI grafted onto ACF@BiOI0.5Cl0.5 is about 18 wt%. During the synergistic process, the grafted PEI and immobilized BiOI0.5Cl0.5 are worked as the adsorbent and the photocatalyst, respectively. In addition, ACF, as flexible, conductive and corrosion-resistant supports, are beneficial to the photocatalytic degradation process. So the obtained composite PEI-g-ACF@BiOI0.5Cl0.5 has a high removal efficiency of contaminants under visible light irradiation with the synergistic effect of adsorption and photocatalytic degradation. And after facial separation without centrifuge, it can be reused without regeneration because of the real-time complete degradation of the adsorbed contaminants on the surface of the composite photocatalyst.

Encapsulation of the heteroepitaxial growth of wide band gap γ-CuCl on silicon substrates

NASA Astrophysics Data System (ADS)

Lucas, F. O.; O'Reilly, L.; Natarajan, G.; McNally, P. J.; Daniels, S.; Taylor, D. M.; William, S.; Cameron, D. C.; Bradley, A. L.; Miltra, A.

2006-01-01

γ-CuCl semiconductor material has been identified as a candidate material for the fabrication of blue-UV optoelectronic devices on Si substrates due to its outstanding electronic, lattice and optical properties. However, CuCl thin films oxidise completely into oxyhalides of Cu II within a few days of exposure to air. Conventional encapsulation of thin γ-CuCl by sealed glass at a deposition/curing temperature greater than 250 °C cannot be used because CuCl interacts chemically with Si substrates when heated above that temperature. In this study we have investigated the behaviour of three candidate dielectric materials for use as protective layers for the heteroepitaxial growth of γ-CuCl on Si substrates: SiO 2 deposited by plasma-enhanced chemical vapour deposition (PECVD), organic polysilsesquioxane-based spin on glass material (PSSQ) and cyclo olefin copolymer (COC) thermoplastic-based material. The optical properties (UV/Vis and IR) of the capped luminescent CuCl films were studied as a function of time, up to 28 days and compared with bare uncapped films. The results clearly show the efficiency of the protective layers. Both COC and the PSSQ layer prevented CuCl film from oxidising while SiO 2 delayed the effect of oxidation. The dielectric constant of the three protective layers was evaluated at 1 MHz to be 2.3, 3.6 and 6.9 for C0C, SiO 2 and PSSQ, respectively.

Nitrosyl Iodide, Ino: Millimeter-Wave Spectroscopy Guided by AB Initio Quantum Chemical Computation

NASA Astrophysics Data System (ADS)

Bailleux, Stephane; Duflot, Denis; Aiba, Shohei; Ozeki, Hiroyuki

2015-06-01

In the series of the nitrosyl halides, XNO (where X = {F, Cl, Br, I}), the millimeter-wave spectrum of INO remains so far unknown. We report our investigation on the first high-resolution rotational spectroscopy of nitrosyl iodide, INO. One of the motivation for this work comes from the growing need in developing a more complete understanding of atmospheric chemistry, especially halogen and nitrogen oxides chemistry that adversely impacts ozone levels. In the family of the nitrogen oxyhalides such as nitrosyl (XNO), nitryl (XNO), nitrite (XONO), and nitrate (XON0_2) halides, those with X = {F, Cl, Br} have been well studied, both theoretically and experimentally. However, relatively little is known about the iodine-containing analogues, although they also are of potential importance in tropospheric chemistry. In 1991, the Fourier-transform IR spectroscopic detection of INO, INO_2 and IONO_2 in the gas phase has been reported The INO molecule was generated by in situ mixing continuously I_2 and NO in a 50-cm long reaction glass tube whose outlet was connected to the absorption cell using a teflon tube. At the time of writing this abstract, 68 μ_a-type transitions (K_a = 0-10), all weak, have been successfully assigned. The hyperfine structures due to both I and N nuclei will also be presented. S.B. and D.D. acknowledge support from the Laboratoire d'Excellence CaPPA (Chemical and Physical Properties of the Atmosphere) through contract ANR-10-LABX-005 of the Programme d'Investissement d'Avenir. I. Barnes, K. H. Becker and J. Starcke, J. Phys. Chem. 1991, 95, 9736-9740.

Factors controlling the geochemical evolution of fumarolic encrustations, Valley of Ten Thousand Smokes, Alaska

USGS Publications Warehouse

Kodosky, L.G.; Keith, T.E.C.

1993-01-01

Factor and canonical correlation analysis of geochemical data from eight fossil fumaroles suggest that six major factors controlled the formation and evolution of fumarolic encrustations on the 1912 ash-flow sheet in the Valley of Ten Thousand Smokes (VTTS). The six-factor solution model explains a large proportion (low of 74% for Ni to high of 99% for Si) of the individual element data variance. Although the primary fumarolic deposits have been degraded by secondary alteration reactions and up to 75 years of weathering, the relict encrustations still preserve a signature of vapor-phase element transport. This vapor-phase transport probably occurred as halide or oxyhalide species and was significant for As, Sb and Br. At least three, and possibly four, varied temperature leaching events affected the fumarolic deposits. High-temperature gases/liquids heavily altered the ejecta glass and mineral phases adjacent to the fumarolic conduit. As the fumaroles cooled. Fe-rich acidic condensate leached the ejecta and primary fumarolic deposits and resulted in the subsequent precipitation of Fe-hydroxides and/or Fe-oxides. Low- to ambient-temperature leaching and hydration reactions generated abundant hydrated amorphous phases. Up to 87% of the individual element data variance is apparently controlled by the chemistry of the ejecta on which the relict encrustations are found. This matrix chemistry factor illustrates that the primary fumarolic minerals surrounding the active VTTS vents observed by earlier workers have been effectively removed by the dissolution reactions. Element enrichment factors calculated for the VTTS relict encrustations support the statistical factor interpretations. On the average, the relict encrustations are enriched, relative to visibly unaltered matrix protolith, in As, Br, Cr, Sb, Cu, Ni, Pb, Fe, and LOI (an indirect measure of sample H2O content). ?? 1993.

Photo-reduction of bromate in drinking water by metallic Ag and reduced graphene oxide (RGO) jointly modified BiVO4 under visible light irradiation.

PubMed

Chen, Fei; Yang, Qi; Zhong, Yu; An, Hongxue; Zhao, Jianwei; Xie, Ting; Xu, Qiuxiang; Li, Xiaoming; Wang, Dongbo; Zeng, Guangming

2016-09-15

Bromate (BrO3(-)), an oxyhalide disinfection by-product (DBP) in drinking water, has been demonstrated to be carcinogenic and genotoxic. In the current work, metallic Ag and reduced graphene oxide (RGO) co-modified BiVO4 was successfully synthesized by a stepwise chemical method coupling with a photo-deposition process and applied in the photo-reduction of BrO3(-) under visible light irradiation. In this composite, metallic Ag acted as an electron donor or mediator and RGO enhanced the BrO3(-) adsorption onto the surface of catalysts as well as an electron acceptor to restrict the recombination of photo-generated electron-hole pairs. The Ag@BiVO4@RGO composite exhibited greater photo-reduction BrO3(-) performance than pure BiVO4, Ag@BiVO4 and RGO@BiVO4 under identical experimental conditions: initial BrO3(-) concentration 150 μg/L, catalyst dosage 0.5 g/L, pH 7.0 and visible light (λ > 420 nm). The photoluminescence spectra (PL), electron-spin resonance (ESR), photocurrent density (PC) and electrochemical impedance spectroscopy (EIS) measurements indicated that the modified BiVO4 enhanced the photo-generated electrons and separated the electron-hole pairs. The photocatalytic reduction efficiency for BrO3(-) removal decreased with the addition of electron quencher K2S2O8, suggesting that electrons were the primary factor in this photo-reduction process. The declining photo-reduction efficiency of BrO3(-) in tap water should attribute to the consumption of photo-generated electrons by coexisting anions and the adsorption of dissolved organic matter (DOM) on graphene surface. The overall results indicate a promising application potential for photo-reduction in the DBPs removal from drinking water. Copyright © 2016 Elsevier Ltd. All rights reserved.

Why chlorate occurs in potable water and processed foods: a critical assessment and challenges faced by the food industry.

PubMed

Kettlitz, Beate; Kemendi, Gabriella; Thorgrimsson, Nigel; Cattoor, Nele; Verzegnassi, Ludovica; Le Bail-Collet, Yves; Maphosa, Farai; Perrichet, Aurélie; Christall, Birgit; Stadler, Richard H

2016-06-01

Recently, reports have been published on the occurrence of chlorate mainly in fruits and vegetables. Chlorate is a by-product of chlorinating agents used to disinfect water, and can be expected to be found in varying concentrations in drinking water. Data on potable water taken at 39 sampling points across Europe showed chlorate to range from < 0.003 to 0.803 mg l(-1) with a mean of 0.145 mg l(-1). Chlorate, however, can also be used as a pesticide, but authorisation was withdrawn in the European Union (EU), resulting in a default maximum residue limit (MRL) for foods of 0.01 mg kg(-1). This default MRL has now led to significant problems in the EU, where routinely disinfected water, used in the preparation of food products such as vegetables or fruits, leaves chlorate residues in excess of the default MRL, and in strict legal terms renders the food unmarketable. Due to the paucity of data on the chlorate content of prepared foods in general, we collated chlorate data on more than 3400 samples of mainly prepared foods, including dairy products, meats, fruits, vegetables and different food ingredients/additives. In total, 50.5% of the food samples contained chlorate above 0.01 mg kg(-1), albeit not due to the use of chlorate as a pesticide but mainly due to the occurrence of chlorate as an unavoidable disinfectant by-product. A further entry point of chlorate into foods may be via additives/ingredients that may contain chlorate as a by-product of the manufacturing process (e.g. electrolysis). Of the positive samples in this study, 22.4% revealed chlorate above 0.1 mg kg(-1). In the absence of EU levels for chlorate in water, any future EU regulations must consider the already available WHO guideline value of 0.7 mg l(-1) in potable water, and the continued importance of the usage of oxyhalides for disinfection purposes.

Transport Properties Of PbI2 Doped Silver Oxysalt Based Amorphous Solid Electrolytes

NASA Astrophysics Data System (ADS)

Shrisanjaykumar Jayswal, Manishkumar

Solid electrolytes are a class of materials that conduct electricity by means of motion of ions like Ag+, Na+, Li +, Cu+, H+, F-, O -2 etc. in solid phase. The host materials include crystalline, polycrystalline, glasses, polymers and composites. Ion conducting glasses are one of the most sought after solid electrolytes that are useful in various electrochemical applications like solid state batteries, gas sensors, supercapacitors, electrochromic devices, to name a few. Since the discovery of fast silver ion transport in silver oxyhalide glasses at the end of the 1960s, many glasses showing large ionic conductivity up to 10-4 10-2 S/cm at room temperature have been developed, chiefly silver and copper ion conductors. The silver ion conducting glasses owe their high ionic conductivity mainly to stabilized alpha-AgI. AgI, as we know, undergoes a structural phase transition from wurtzite (beta phase) at room temperature to body centered cubic (alpha phase) structure at temperatures higher than 146 °C. The alpha-AgI possesses approximately six order of higher ionic conductivity than beta-AgI. The high ionic conductivity of alpha-AgI is attributed to its molten sublattice type of structure, which facilitates easy Ag+ ion migration, like a liquid. And hence, several attempts have been made to stabilize it at room temperature in crystalline as well as non-crystalline hosts like oxide and non-oxide glasses. Recently, in order to stabilize AgI in glasses, instead of directly doping it, indirect routes have also been explored. Where, a metal iodide salt along with silver oxide or silver phosphate is taken and an exchange reaction permitted by Hard and Soft, Acid and Base (HSAB) principle occurs between the two and AgI and metal oxide form in the glass forming melt. Work done in the present thesis has been organized in seven chapters as follows: Chapter 1: A review and background information of different solid electrolyte materials and their development is presented. Along with that a detailed review on fast ion conducting glasses is included. At the end of the chapter, the aim of the present work has been given. Chapter 2: A discussion about various theoretical models to explain fast ion conduction mechanism in superionic conductors in general and superionic conducting glasses in particular is given. In addition to that, impedance spectroscopy and its various formalisms are discussed. Chapter 3: This chapter describes the method of preparation of the glass samples and various characterizations and techniques to study their various properties. Chapter 4: Physical properties of the prepared glass samples are studied and discussed in this chapter. The glass samples are found to be fully amorphous as exhibited by x-ray diffraction studies. The density of the prepared samples is increasing consistently with increasing PbI 2 content in the glass. For glass series (a), the molar volume also increases with PbI2 content. However, for glass series (b) and (c), molar volume is reducing with increasing PbI2 content, showing that glass is getting compacted with increasing PbI2 content. Chapter 5: Transport properties of the prepared glass samples have been investigated using impedance spectroscopy and its various formalisms. The chapter discusses DC conductivity, AC conductivity, dielectric permittivity and modulus analysis of the obtained impedance spectra. The sigma' spectra were scaled using Summerfield scaling law using sigmaDCT as the scaling factor for frequency axis and a well defined Time-Temperature Superposition (TTS) is observed as a function of temperature. The dielectric spectra show the presence of a dielectric relaxation in all glass samples. The dielectric permittivity, epsilon', spectra were scaled using the scaling law given by Sidebottom. The modulus spectra exhibit non-Debye relaxation of Ag+ ions and could be explained using KWW (Kohlrausch-Williams-Watts) decay function. Scaling analysis of the modulus spectra as a function of temperature suggest of invariance of ion relaxation process with changing temperatures. Chapter 6: Solid state battery studies: This chapter discusses about "solid state batteries" prepared by using the best conducting glass composition, from each glass Battery discharge characteristics, polarization measurements and other battery parameters like battery capacity, power density, energy, specific power etc. have been evaluated and summarized. Chapter 7: A summary of the work done and future prospects are discussed. (Abstract shortened by ProQuest.).