Low-temperature thermal conductivity of the substrate material YAlO3 and its unconventional sister compound YbAlO3

TL;DR

This study measures the thermal conductivity of YAlO3 and YbAlO3 single crystals from 2 K to 300 K, revealing their suitability for low-temperature applications and minimal effects of Y-Yb exchange on phonon transport.

Contribution

It provides detailed thermal conductivity data for YAlO3 and YbAlO3, highlighting anisotropy in YAlO3 and the impact of Y-Yb exchange, which was previously not well characterized.

Findings

YAlO3 has moderate thermal conductivity anisotropy with weak temperature dependence.

YbAlO3's thermal conductivity measurements are limited by crystal size, but show similar phonon transport behavior.

YAlO3 is suitable for low-temperature applications like lasers and detectors.

Abstract

We present thermal conductivity data on single crystals of YAlO3 and YbAlO3 for temperatures between 2 K and 300 K and the heat current along b and c. Both materials are very good thermal conductors in the investigated temperature range. The thermal conductivity in these electrical insulators is due to phonons. The effect of Y-Yb exchange is found to be rather small despite the considerable difference in density and average atomic mass. For YAlO3 we find a moderate thermal conductivity anisotropy with weak temperature dependence and a ratio of c to b direction between at most 1 and 2.2. It is discussed with regard to the velocities of sound and relevant scattering processes. For YbAlO3 the small crystal size limits the precision of absolute thermal conductivity values and does not allow drawing conclusions on the anisotropy. Our results on YAlO3 confirm that the material is suitable for applications requiring a good thermal conductivity at temperatures down to liquid helium, such as lasers, substrates, and detectors.