Predicted thermoelectric properties of olivine-type Fe2GeCh4 (Ch = S, Se and Te)

TL;DR

This study uses first-principles calculations to analyze the thermoelectric properties of olivine-type Fe2GeCh4 compounds, revealing high thermopower especially in S and Se variants and identifying promising thermoelectric candidates.

Contribution

It provides the first theoretical analysis of thermoelectric properties of Fe2GeCh4 compounds, highlighting the impact of band structure on thermopower and anisotropic electrical conductivity.

Findings

High thermopower in S and Se compounds due to flat bands.

Good agreement with experimental thermopower at room temperature.

Fe2GeS4 and Fe2GeSe4 identified as promising thermoelectric materials.

Abstract

We present here the thermoelectric properties of olivine-type Fe2GeCh4 (Ch = S, Se and Te) using the linear augmented plane wave method based on first principles density functional calculations. The calculated transport properties using the semi-local Boltzmann transport equation reveal very high thermopower for both S and Se-based compounds compared to their Te counterparts. The main reason for this high thermopower is the quasi-flat nature of the bands at the valence and conduction band edges. The calculated thermopower of Fe2GeCh4 is in good agreement with the experimental reports at room temperature, with the carrier concentration around 1018-1019cm-3. All the investigated systems show an anisotropic nature in their electrical conductivity, resulting in a value less than the order of 102 along the a-axis compared to the b- and c-axes. Among the studied compounds, Fe2GeS4 and Fe2GeSe4 emerge as promising candidates with good thermoelectric performance.