Ultra-low thermal conductivity and improved thermoelectric performance in La2O3-dispersed Bi2Sr2Co2Oy ceramics

Abstract

Thermoelectric materials are functional materials that directly convert heat energy and electric energy into each other. Nano-second-phase dispersion is an effective strategy to improve the energy conversion efficiency of thermoelectric materials through the energy filtering effect and the phonon scattering effect. In this study, the solid-state reaction method was used to prepare Bi2Sr2Co2Oy + l wt% La2O3 (l = 0.0, 0.1, 0.25, 0.5, 1.75) thermoelectric composites. An ultra-low thermal conductivity of 0.58 W/Km at 923 K was obtained by dispersing a small quantity of La2O3 as the nano-second-phase additive in the Bi2Sr2Co2Oy matrix. This was attributed to the increased hetero-interfaces and improved phonon scattering through the grain refinement effect. The dimensionless thermoelectric figure of merit (ZT) values of Bi2Sr2Co2Oy + 0.25 wt% La2O3 reached 0.28 at 923 K when their power factors were combined with littlechange, which was 21 % higher than that of the un-optimised pristine Bi2Sr2Co2Oy.