Structural phase transitions of (Bi1−xSbx)2(Te1−ySey)3 compounds under high pressure and the influence of the atomic radius on the compression processes of tetradymites

Abstract

Recently, A₂B₃-type tetradymites have developed into a hot topic in physical and material research fields, where the A and B atoms represent V and VI group elements, respectively. In this study, in situ angle-dispersive X-ray diffraction measurements were performed on Bi₂Te₂Se, BiSbTeSe₂, and Sb₂Te₂Se tetradymites under high pressure. Bi₂Te₂Se transforms from a layered rhombohedral structure (phase I) into 7-fold monoclinic (phase II) and body-centered tetragonal (phase IV) structures at about 8.0 and 14.3 GPa, respectively, without an 8-fold monoclinic structure (phase III) similar to that in Bi₂Te₃. Thus, the compression behavior of Bi₂Te₂Se is the same as that of Bi₂Se₃, which could also be obtained from first-principles calculations and in situ high-pressure electrical resistance measurements. Under high pressure, BiSbTeSe₂ and Sb₂Te₂Se undergo similar structural phase transitions to Bi₂Te₂Se, which indicates that the compression process of tellurides can be modulated by doping Se in Te sites. According to these high-pressure investigations of A₂B₃-type tetradymites, the decrease of the B-site atomic radius shrinks the stable pressure range of phase III and expands that of phase II, whereas the decrease of the A-site atomic radius induces a different effect, i.e. expanding the stable pressure range of phase III and shrinking that of phase II. The influence of the atomic radius on the compression process of tetradymites is closely related to the chemical composition and the atom arrangement in the quintuple layer.