Rhombohedral GeSe Thermoelectric Breakthrough by Strategic Pb Alloying

Researchers reported stabilizing pure cubic germanium selenide under ambient conditions using a 10% alloying concentration of antimony telluride, according to a study abstract. The work introduces metavalent alloying and vacancy engineering as strategies to facilitate the orthorhombic-to-cubic phase transition. The abstract said the metavalently bonded cubic phase features lower cation vacancy formation energy, reduced bandgap, enhanced band degeneracy, weaker chemical bonding, stronger lattice anharmonicity, and multiple phonon scattering centers compared to the covalently bonded orthorhombic phase. These properties synergistically improve the power factor and suppress lattice thermal conductivity. Subsequent trace lead doping further reduced lattice thermal conductivity, achieving a figure of merit of 1.38 at 723 Kelvin in cubic (Ge0.95Pb0.05Se)0.9(Sb2Te3)0.1, along with an energy conversion efficiency of 6.13% under a 430 Kelvin temperature difference. The results advance practical application of GeSe-based alloys for medium-temperature power generation and provide insights into the phase transition mechanism in chalcogenides.