Thermal expansion coefficients of Bi_2Se_3 and Sb_2Te_3 crystals from 10 K to 270 K

摘要

Lattice constant of Bi_2Se_3 and Sb_2Te_3 crystals is determined by x-ray powder diffraction measurement in a wide temperature range. Linear thermal expansion coefficients (a) of the crystals are extracted, and considerable anisotropy between α_‖ and α_⊥ is observed. The low temperature values of a can be fit well by the Debye model, while an anomalous behavior at above 150 K is evidenced and explained. Griineisen parameters of the materials are also estimated at room temperature.