Thermal conductivity of Barium Bismuthate at low temperatures

TL;DR

This study presents the first measurement of thermal conductivity in pristine BaBiO₃ across a wide temperature range, revealing glass-like features at low temperatures and crystalline behavior at high temperatures, contributing to understanding heat transport in complex oxides.

Contribution

First thermal conductivity measurement of BaBiO₃, linking structural distortions to phononic heat transport in this insulating perovskite.

Findings

Glass-like thermal conductivity features at low temperatures

Crystalline behavior with a downturn at high temperatures

Comparison with similar perovskite oxides

Abstract

The perovskite BaBiO$_3$ crystallizes in a cubic structure and undergoes structural transitions toward lower symmetry phases upon cooling. The two low-temperature monoclinic phases are insulating, and the origin of this unexpected non-metallic character has been under debate. Both monoclinic phases exhibit tilting and breathing distortions, which are connected with the insulating nature of this compound and may have important effects on phononic heat conductivity. Here, we report the first thermal conductivity measurement, $\kappa$(T), in pristine polycrystalline BaBiO$_3$ from 1.5 K to 310 K. At low and intermediate temperatures, we observe features reminiscent of a glass-like behavior, whereas at high-temperatures we find a downturn - typical of a crystalline solid. We compare our findings with available data of other recently investigated perovskite oxides displaying similar temperature dependence.