Anisotropic Thermal Expansion of Zirconium Diboride: An Energy-Dispersive X-Ray Diffraction Study
SciTech Connect
Paxton, William A.; Özdemir, Tevfik E.; Şavklıyıldız, İlyas; Whalen, Terence; Biçer, Hülya; Akdoğan, Enver Koray; Zhong, Zhong; Tsakalakos, Thomas
2016-01-01
Zirconium diboride (ZrB_{2}) is an attractive material due to its thermal and electrical properties. In recent years, ZrB_{2}has been investigated as a superior replacement for sapphire when used as a substrate for gallium nitride devices. Like sapphire, ZrB_{2}has an anisotropic hexagonal structure which defines its directionally dependent properties. However, the anisotropic behavior of ZrB_{2}is not well understood. In this paper, we use energy-dispersive synchrotron X-ray diffraction to measure the thermal expansion of polycrystalline ZrB_{2}powder from 300 to 1150 K. Nine Bragg reflections are fit using Pseudo-Voigt peak profiles and used to compute the$a$and$c$lattice parameters using a nonlinear least-squares approximation. The temperature-dependent instantaneous thermal expansion coefficients are determined for each$a$-axis and$c$-axis direction and are described by the following equations:${\alpha}_{a}$= ($4.1507\times {10}^{-6}$+$5.1086$×${10}^{-9}(T-293.15)$)/($1+4.1507$×