First-Principles Investigation of the Physical and Thermoelectric Properties of Chalcogenide Compounds for Waste-Heat Recovery

Abstract: Improving energy efficiency by recovering waste heat and providing thermal protection is of high technological importance. This work investigates the chalcogenide compounds CdGa2Te4 and ZnGa2Te4 using density functional theory and BoltzTraP2 calculations. Both materials are dynamically stable, brittle, and elastically anisotropic. Electronic structure calculations show direct band gaps that range from 1.0 to 2.2 electronvolt. Carrier effective masses are favorable, with CdGa2Te4 showing light electrons equal to 0.21 times the free electron mass and ZnGa2Te4 showing moderately heavy carriers equal to 0.39 times the free electron mass. Thermoelectric transport calculations yield large Seebeck coefficients of about 108 to 119 microvolt per kelvin. The thermoelectric figure of merit ZT increases from about 0.4 at 50 K to about 0.78 at 800 kelvin, indicating promising thermoelectric performance. For thermal barrier coating applications, both compounds combine ultralow lattice thermal conductivity with moderate melting points around 790 to 850 K and small thermal expansion coefficients, which helps resist thermal stress. Overall, CdGa2Te4 and ZnGa2Te4 are multifunctional materials suitable for efficient waste heat recovery and durable thermal barrier operation below 900 K.