Thermophysical and Thermodynamic Properties of the Ternary Semiconductor Compound Au3in5se9 Over a Wide Temperature Range

In this work, the temperature dependence of the heat capacity of the ternary semiconductor compound \(\:Au₃In₅Se₉\) has been experimentally investigated over the temperature range 65–300 K using adiabatic calorimetry. Based on the experimental heat-capacity data, the principal thermodynamic functions-enthalpy and entropy-were determined by numerical integration. Special attention was paid to the analysis of the temperature evolution of the Debye characteristic temperature, which provides important information on lattice vibrational dynamics and phonon-related processes in the crystal. The Debye temperature was evaluated within the framework of a three-dimensional elastic-continuum model, considering the hexagonal crystal structure of the compound. The obtained results reveal a stable thermodynamic behaviour of \(\:Au₃In₅Se₉\) over the investigated temperature interval and demonstrate the influence of anharmonic lattice effects at elevated temperatures. The relationship between the thermal properties and the crystal structure of the compound is discussed, highlighting the relevance of the obtained data for further thermophysical modelling and potential thermoelectric applications.