Thermophysical properties of zinc gallate

Abstract

Complex spinel oxides AB 2 O 4 are inorganic materials, which, due to their refractoriness and a whole range of functional properties, are widely in demand in various fields of the power industry and electronics. This paper reports on the results of an experimental study of the thermophysical properties of zinc gallate, which is a promising material for optoelectronics, solid-state lighting and catalytic and biomedical applications. Highly dispersed single-phase ZnGa 2 O 4 powder was synthesised by gel combustion. As a result of high-temperature sintering of pressed powder blanks, ZnGa 2 O 4 ceramics (≈95% of the theoretical) were produced. According to SEM, the material has a dense microstructure consisting of micron-sized spinel grains. The heat capacity of the material produced was investigated by relaxation, adiabatic and differential scanning calorimetry. By combining experimental data in the range of 8.7–1276 K, a single consistent temperature dependence of ZnGa 2 O 4 heat capacity was obtained for the first time. The analysis of the curve obtained showed no signs of phase transitions in the studied temperature range. Based on the results of calorimetric measurements within the range 0 K–1276 K, the temperature dependences of heat capacity, entropy, enthalpy change and Gibbs energy function were calculated. The absolute entropy of ZnGa 2 O 4 spinel at 298.15 K was 120.23 J/(K·mol). The thermal diffusivity of ZnGa 2 O 4 ceramics measured by laser flash method was 2.6 mm 2 /s at 300 K, decreasing to 0.46 mm 2 /s at 1174 K. Its thermal conductivity calculated using experimental data on heat capacity and thermal diffusivity at room temperature was 7.6 W/(m·K). The obtained data are of interest in terms of improving materials based on ZnGa 2 O 4 , which are promising for use in light-emitting diodes and new-generation power semiconductor devices. • Ultra-fine ZnGa 2 O 4 powder was synthesised by a PVA-assisted gel combustion method. • High-density ZnGa 2 O 4 ceramics with micrometre-sized grains (>1 μm) were produced. • The temperature dependence of heat capacity was measured from 8.7 K to 1276 K. • Thermal diffusivities and thermal conductivities of the ceramics prepared were studied.