Phase separation and nanostructuring in the thermoelectric material PbTe1-xSx

TL;DR

This study investigates the structural behavior of PbTe1-xSx thermoelectric materials, revealing phase separation, spinodal decomposition, and nanostructuring that contribute to low thermal conductivity.

Contribution

It provides detailed insights into the phase separation and nanostructuring mechanisms in PbTe1-xSx, highlighting their impact on thermoelectric properties.

Findings

Samples with x > 0.25 are macroscopically phase separated.

Quenched x=0.5 sample shows partial spinodal decomposition.

x=0.16 sample exhibits nanostructuring leading to low thermal conductivity.

Abstract

The average and local structures of the (PbTe)1-x(PbS)x system of thermoelectric materials has been studied using the Rietveld and atomic pair distribution function (PDF) methods. Samples with 0:25 < x are macroscopically phase separated. Phase separation was suppressed in a quenched x = 0:5 sample which, nonetheless, exhibited a partial spinodal decomposition. The promising thermoelectric material with x = 0:16 showed intermediate behavior. Combining TEM and bulk scattering data suggests that the sample is a mixture of PbTe rich material and a partially spinodally decomposed phase similar to the quenched 50% sample. This results in a nano-meter scale inhomogeneous material that accounts for its very low thermal conductivity.