Insight on thermodynamic and thermoelectric properties of Ge based perovskites AGeO₃ (A = Mg, Cd) for energy harvesting applications: A DFT approach

In this manuscript, transport properties like thermoelectric and thermodynamic properties of AGeO₃ (A = Mg, Cd) perovskites have been performed in detail along with effect of chemical potential on various thermoelectric parameters. Furthermore, we present the electronic effects and thermodynamic stability of these materials. The MgGeO₃ and CdGeO₃ alloys have a gap of 3.368 and 2.555 eV, respectively, making them indirect band gap semiconductors. Furthermore, using a constant relaxation time approximation and semiclassical Boltzmann theory, the thermoelectric (TE) properties of both materials have been studied. The lattice thermal conductivity magnitudes for MGeO₃ and CdGeO₃ are 7.47 W/mK and 21.55 W/mK, respectively, at 300 K. Power Factor (PF) has been measured at approximately 0 chemical potential, or approximately 14 (10¹¹ W/K² ms) at 1200 K, 7.5 (10¹¹ W/K² ms) at 700 K, and 3.5 (10¹¹ W/K² ms) at 300 K for both MgGeO₃ and CdGeO₃. At room temperature, the electrical conductivities of MgGeO₃ and CdGeO₃ were measured to be 1.43 × 10¹⁵W/mK and 1.08 × 10¹⁵W/mK, respectively. Over a broad temperature range (0–1200 K), the thermodynamic parameters, such as heat capacity, entropy, thermal expansion, and Debye temperature, were also computed and discussed.