Implication of Alloying The Anionic Framework in Mg₃Sb₂ for p-Type Zintl Thermoelectrics

Solid solutions of <i>n</i>-type Mg₃Sb₂ has garnered growing attention due to its remarkable thermoelectric potential for harnessing low grade waste heat. However, achieving high performing <i>p</i>-type conduction around room temperature has remained challenging, fundamentally due to greater degeneracy in conduction band relatively to the valence band. As a Zintl compound, <i>β</i>-Mg₃Sb₂ crystal structure constitutes of an anionic framework of double layer [Mg₂Sb₂]²⁻ wherein Mg²⁺ cations are located between these layers. In this work, we present the implication of (Bi, Sn, Ge, Te) alloying at the anionic framework of Mg₃Sb₂ solid solutions to favorably tune the <i>p</i>-type conduction for attaining higher power factors by band engineering. Altering the anionic framework through alloying resulted in modifying the electronic structure to enhance the valley degeneracy at the top of valence bands. Simultaneously, the prospects of enhancing phonon scattering by the distorted lattice, point defects, and nano-precipitates was examined for attaining lower lattice thermal conductivity at near room temperature. The alloyed <i>p</i>-type Mg₃(Sb,Bi,Ge,Sn,Te)₂with its tailored properties, shows promising potential as an economical alternative to α-MgAgSb, thereby facilitating the practical realization of Mg₃Sb₂-based thermoelectric power generators for harnessing low-grade heat.