Monoclinic structure and electrical properties of metastable Sb 2 Te 3 and Bi 0.4 Sb 1.6 Te 3 phases

We synthesized metastable phases of Sb 2 Te 3 and Bi 0.4 Sb 1.6 Te 3 by quenching after high‐pressure (4 GPa) and high‐temperature (873 K) treatment and specify them as m‐Sb 2 Te 3 and m‐Bi 0.4 Sb 1.6 Te 3 . The metastable phases of both alloys crystallize in the same structure type. The crystal structure of metastable phases, determined by the powder X‐ray and electron diffraction methods, is monoclinic (C2/m). The cell dimensions of m‐Sb 2 Te 3 are: a   =  15.644(80) Å, b  = 4.282(8) Å, c  = 9.382(20) Å, β  = 89.70(5)°, the cell dimensions of m‐Bi 0.4 Sb 1.6 Te 3 diverge by a hundredth of angstrom units and monoclinic angle – by tenths of a degree. We revealed that the structure of β‐Sb 2 Te 3 ‐phase, observed in situ under high pressure, may be represented as a structure of m‐Sb 2 Te 3 ‐type and thus it can be retained at ambient conditions. We investigated the temperature dependencies of the electrical resistivity and the Hall coefficient of recovered samples in the range of T  = 1.8–450 K. The structure of metastable phases possesses metallic type bonding and m‐Sb 2 Te 3 phase is superconductive at T  < 2 K. The ab initio study verified metallic character of the quenched phases. After annealing at 673 K during 2.5 h the structures of the recovered samples Sb 2 Te 3 and Bi 0.4 Sb 1.6 Te 3 returned to initial rhombohedral symmetry.