High thermoelectric performance and low thermal conductivity of densified LaOBiSSe

TL;DR

This study demonstrates that densified LaOBiSSe exhibits high thermoelectric performance with a figure-of-merit around 0.36 at 650 K, influenced by crystal orientation affecting electrical and thermal properties.

Contribution

The paper reports the synthesis and characterization of densified LaOBiSSe with notable thermoelectric performance and low thermal conductivity, highlighting orientation effects.

Findings

Highest figure-of-merit ~0.36 at 650 K

Thermal conductivity varies with orientation

Electrical properties depend on crystal orientation

Abstract

In this study, we examined the thermoelectric properties of the layered bismuth-chalcogenide-based (BiCh2-based) compound LaOBiSSe, which is expected to be a new candidate material for thermoelectric applications. Densified samples were obtained with a hot-press method. The results of the X-ray diffraction measurements showed that the samples obtained were weakly oriented. This affected the resistivity (r) and Seebeck coefficient (S) of the samples because they are dependent upon the orientation of the crystal structure. The values obtained for the power factor (S2/r) when measured perpendicular to the pressing direction (P1) were higher than that when measured parallel to the pressing direction (P2). The thermal conductivity (k) of the samples was also sensitive to the orientation. The values of k measured along P2 were lower than that measured along P1. The highest figure-of-merit (approximately 0.36) was obtained at around 650 K in both directions, i.e., P1 and P2.