Thermal Expansion Coefficients of Bi$_2$Se$_3$ and Sb$_2$Te$_3$ Crystals from 10 K to 270 K

TL;DR

This study measures the thermal expansion coefficients of Bi2Se3 and Sb2Te3 crystals across 10 K to 270 K, revealing anisotropic behavior and deviations from Debye model at higher temperatures.

Contribution

It provides detailed measurements of anisotropic thermal expansion and analyzes deviations from theoretical models for Bi2Se3 and Sb2Te3 crystals.

Findings

Significant anisotropy in thermal expansion coefficients

Debye model fits low-temperature data well

Anomalous expansion behavior observed above 150 K

Abstract

Lattice constant of Bi$_2$Se$_3$ and Sb$_2$Te$_3$ crystals is determined by X-ray powder diffraction measurement in a wide temperature range. Linear thermal expansion coefficients ($\alpha$) of the crystals are extracted, and considerable anisotropy between $\alpha_\parallel$ and $\alpha_\perp$ is observed. The low temperature values of $\alpha$ can be fit well by the Debye model, while an anomalous behavior at above 150 K is evidenced and explained. Gr\"uneisen parameters of the materials are also estimated at room temperature.