The coefficients of thermal expansion of boron arsenide (B12As2) between 25 °C and 850 °C

Abstract

The present investigation was undertaken to determine the coefficients of thermal expansion for the boron-rich compound semiconductor icosahedral boron arsenide (B12As2). B12As2 powder was synthesized in a sealed quartz ampoule containing boron and arsenic heated to 1100°C and 600°C respectively for 72h. The lattice constants of the B12As2 were measured by high temperature X-ray diffraction (HTXRD) between 25°C and 850°C. The average lattice coefficients of thermal expansion were calculated perpendicular and parallel to the 〈111〉 axis in the rhombohedral setting (equivalent to the a and c axes in the hexagonal setting) as 4.9×10−6K−1 and 5.3×10−6K−1, respectively. The average unit cell volumetric coefficient of thermal expansion was 15.0×10−6K−1. Knowing these values can be useful in explaining the cracking that occurs in heteroepitaxial B12As2 thin films and crystals precipitated from metal solutions upon cooling from their synthesis temperatures.