Pb2MgXO6 (X = W and Te) Double Perovskites: New Insights into Their Electronic, Elastic, Optic and Thermoelectric Properties

Abstract

We carried out a theoretical study in which we explored the mechanical, optoelectronic, and thermoelectric properties of Pb₂Mg(W/Te)O₆ double perovskites with first-principles density functional approach and Boltzmann transport theory. The calculations were performed with the Perdew–Burke–Ernzerhof generalized gradient approximation and the Heyd–Scuseria–Ernzerhof functional (HSE06). Examination of structural stability is conducted through the analysis of the tolerance factor. The analysis of elastic constants within generalized gradient approximations reveals that both compounds satisfy the Born stability criteria and have excellent machinability. Moreover, they have a ductile nature with metallic bonding and a low Debye temperature. The examined materials possessed a significant effective mass in both compounds and direct bandgaps with values 2.4 eV (3.7 eV) for Pb₂MgWO₆ and 2.7 eV (4.2 eV) for Pb₂MgTeO₆ obtained within Perdew–Burke–Ernzerhof generalized gradient approximation (hybrid HSE06), respectively. Therefore, Pb₂Mg(W/T)O₆ demonstrates different photovoltaic capabilities with a low power conversion efficiency of ~10% employing HSE06, which are the appropriate attributes for the solar cell photoelectric absorption layers. Furthermore, the examined materials have excellent substantial thermopower, as well as figures of merit of 2.46 (2.67) and 2.26 (2.47) for Pb₂MgTeO₆ and Pb₂MgWO₆, respectively, ensuring the appropriate application for thermoelectric devices.