Table of Contents
Journal of Ceramics
Volume 2016, Article ID 8346563, 5 pages
http://dx.doi.org/10.1155/2016/8346563
Research Article

Anisotropic Thermal Expansion of Zirconium Diboride: An Energy-Dispersive X-Ray Diffraction Study

1Materials Science and Engineering, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA
2Photon Sciences, Brookhaven National Laboratory, Upton, NY 11973, USA

Received 31 March 2016; Revised 10 May 2016; Accepted 12 May 2016

Academic Editor: Yuan-hua Lin

Copyright © 2016 William A. Paxton et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Zirconium diboride (ZrB2) is an attractive material due to its thermal and electrical properties. In recent years, ZrB2 has been investigated as a superior replacement for sapphire when used as a substrate for gallium nitride devices. Like sapphire, ZrB2 has an anisotropic hexagonal structure which defines its directionally dependent properties. However, the anisotropic behavior of ZrB2 is not well understood. In this paper, we use energy-dispersive synchrotron X-ray diffraction to measure the thermal expansion of polycrystalline ZrB2 powder from 300 to 1150 K. Nine Bragg reflections are fit using Pseudo-Voigt peak profiles and used to compute the and lattice parameters using a nonlinear least-squares approximation. The temperature-dependent instantaneous thermal expansion coefficients are determined for each -axis and -axis direction and are described by the following equations: = ( + × )/( × + ) and = ( + )/( + ). Our results are within range of previously reported values but describe the temperature anisotropy in more detail. We show that anisotropic expansion coefficients converge to the same value at about 780 K and diverge at higher temperatures. Results are compared with other reported values.