Synthesis, Crystal Structure, and Thermoelectric Properties of Layered Antimony Selenides REOSbSe2 (RE = La, Ce)

TL;DR

This study investigates the crystal structure and thermoelectric properties of layered antimony selenides REOSbSe2 (RE = La, Ce), revealing their potential for thermoelectric applications due to their low thermal conductivity and semiconducting nature.

Contribution

First experimental characterization of REOSbSe2 layered antimony selenides, including structure, optical band gaps, and thermoelectric properties, inspired by prior theoretical predictions.

Findings

REOSbSe2 compounds are n-type semiconductors.

Low thermal conductivities of 1.5 and 0.8 W/mK for La and Ce variants.

F- doping did not significantly improve electrical conductivity.

Abstract

Inspired by the recent first-principles calculations showing the high thermoelectric performance of layered pnictogen chalcogenides, we experimentally characterise the crystal structure and high-temperature transport properties of the layered antimony selenides REOSbSe2 (RE = La, Ce). The crystal structure of REOSbSe2 was the tetragonal P4/nmm space group, consisting of alternate stacks of SbSe2 and REO layers. These two compounds were n-type semiconductors. The optical band gaps of LaOSbSe2 and CeOSbSe2 were evaluated to be 1.0 and 0.6 eV, respectively. The room-temperature thermal conductivity was 1.5 Wm-1K-1 for RE = La and 0.8 Wm-1K-1 for RE = Ce. These relatively low thermal conductivities were comparable to those of isostructural layered bismuth chalcogenides. We substituted O2- with F- ions to introduce electrons as charged carriers to optimize the thermoelectric performance, but increasing the electrical conductivity was still challenging.