Thermoelectric properties of inverse perovskites A₃TtO (A = Mg, Ca; Tt = Si, Ge): Computational and experimental investigations

Oxygen-containing inverse perovskites represent one possible solution to reduce the cost and enhance the sustainability of thermoelectric materials. Although oxygen-containing compounds may be thought to reduce the electronic mobility and thus the thermoelectric performance, computational studies on A₃TtO (A = Mg, Ca; Tt = Si, Ge) revealed that they exhibit high electrical conductivity originating from Dirac cones at valence and conduction bands. High Seebeck coefficients were predicted arising from multiple degenerate bands, leading to enhanced power factors, and low thermal conductivities were predicted using the minimum thermal conductivity model. These predictions were validated by experimental studies on Ca₃SiO and Ca₃GeO, which were synthesized through high-temperature methods. They adopt an orthorhombic structure (space group Imma). Transport measurements show high Seebeck coefficients and low thermal conductivities for these compounds, confirming their potential for high thermoelectric performance.