Thermal Decomposition Study on CuInSe$_{2}$ Single Crystals

Abstract

The thermal analysis of the chemical vapor transport (CVT)-grown $\hbox {CuInSe}_{2}$ single crystals was carried out by recording the thermogravimetric, differential thermogravimetric and differential thermal analysis curves. All the three thermo-curves were recorded simultaneously by thermal analyzer in the temperature range of ambient to 1080 K in inert nitrogen atmosphere. The thermo-curves were recorded for four heating rates of 5 K $\cdot \,\hbox {min}^{-1}$, 10 K $\cdot \,\hbox {min}^{-1}$, 15 K $\cdot \,\hbox {min}^{-1}$ and 20 K $\cdot \,\hbox {min}^{-1}$. The TG curve analysis showed negligible mass loss in the temperature range of ambient to 600 K, stating the sample material to be thermally stable in this temperature range. Above 601 K to the temperature of 1080 K, the sample showed continuous mass loss. The DTG curves showed two peaks in the temperature range of 601 K to 1080 K. The corresponding DTA showed initial minor exothermic nature followed by endothermic nature up to nearly 750 K and above it showed exothermic nature. The initial exothermic nature is due to absorbed water converting to water vapor, whereas the endothermic nature states the absorption of heat by the sample up to nearly 950 K. Above nearly 950 K the exothermic nature is due to the decomposition of sample material. The absorption of heat in the endothermic region is substantiated by corresponding weight loss in TG. The thermal kinetic parameters of the CVT-grown $\hbox {CuInSe}_{2}$ single crystals were determined employing the non-mechanistic Kissinger relation. The determined kinetic parameters support the observations of the thermo-curves.