Discovery of a metallic oxide with ultralow thermal conductivity

TL;DR

This paper reports a new iridium oxide compound, Bi3Ir3O11, that uniquely combines metallic electrical conductivity with ultralow thermal conductivity, challenging conventional understanding of heat transport in metals.

Contribution

It introduces a novel metallic oxide with ultralow thermal conductivity and elucidates the structural and electronic mechanisms behind this property.

Findings

Bi3Ir3O11 has thermal conductivity near 0.61 W/m·K at 300 K.

The compound's structure promotes metallic conduction and low thermal transport.

Theoretical analysis explains the coexistence of metallicity and ultralow thermal conductivity.

Abstract

A compound with metallic electrical conductivity usually has a considerable total thermal conductivity because both electrons and photons contribute to thermal transport. Here, we show an exceptional example of iridium oxide, Bi3Ir3O11, that concurrently displays metallic electrical conductivity and ultralow thermal conductivity approaching 0.61 W m-1 K-1 at 300 K. The compound crystallizes into a cubic structural framework with space group Pn-3. The edge- and corner-sharing IrO6 octahedra with a mixed Ir4.33+ charge state favor metallic electrical transport. Bi3Ir3O11 exhibits an extremely low lattice thermal conductivity close to the minimum limit in theory owing to its tunnel-like structure with filled heavy atoms Bi rattling inside. Theoretical calculations reveal the underlying mechanisms for the extraordinary compatibility between metallic electrical conductivity and ultralow thermal conductivity. This study may establish a new avenue for designing and developing unprecedented heat-insulation metals.