High-throughput exploration of alloying as design strategy for thermoelectrics

TL;DR

This study uses high-throughput screening of band structure changes upon volume variation to identify alloying strategies that enhance thermoelectric performance in binary silicides and germanides, revealing new promising compounds.

Contribution

It introduces a novel high-throughput methodology to predict alloying effects on thermoelectric properties based on band structure and volume changes.

Findings

Confirmed alloying improves power factor in Mg2Si and Mg2Ge.

Identified six new binary compounds with enhanced transport properties.

Ca2Si and Ca2Ge form stable alloys with Ca2Sn at low temperatures.

Abstract

We explore a material design strategy to optimize the thermoelectric power factor. The approach is based on screening the band structure changes upon a controlled volume change. The methodology is applied to the binary silicides and germanides. We first confirm the effect in antifluorite Mg2Si and Mg2Ge where an increased power factor by alloying with Mg2Sn is experimentally established. Within a high-throughput formalism we identify six previously unreported binaries that exhibit an improvement in their transport properties with volume. Among these, hexagonal MoSi2 and orthorhombic Ca2Si and Ca2Ge have the highest increment in zT with volume. We then perform super-cell calculations on special quasi-random structures to investigate the possibility of obtaining thermodynamically stable alloy systems which would produce the necessary volume changes. We find that for Ca2Si and Ca2Ge the solid solutions with the isostructural Ca2Sn readily forms even at low temperatures.