Solid solutions based on laminated chalcogenides of bismuth and lead in ternary reciprocal Pb, Bi||Se, Te system

Abstract

X-ray diffraction and metallographic studies of solid solution alloys are carried out in the PbSe–Bi2Se3 and PbTe–Bi2Te3 quasi-binary systems. Also, the alloys in the PbTe–Bi2Se3 and PbSe–Bi2Te3 diagonal cross sections of the reciprocal ternary system Pb, Bi||Se, Te are studied in the range of compositions near the solid solution PbTe1-xSex (δ). The PbSe–Bi2Se3 phase diagram is refined and it is shown that the phases with orthorhombic lattices existing in the PbS–Bi2S3 system do not form in the PbSe–Bi2Se3 system. In the Pb, Bi||Se, Te ternary reciprocal system, the presence of extended ranges of quadruple solid solutions of trigonal symmetry based on seven compounds is detected: Pb2Bi2Te5, Pb3Bi4Te9, PbBi2Te4, Pb2Bi6Te11, PbBi4Te7, PbBi6Te10, and PbBi8Te13 from the homologous series [PbTe]m[Bi2Te3]n. The extent of the δ range of the solid solution with NaCl cubic structure is established at the PbTe–PbSe side. It is found that the extent of the δ-solid solution region decreases as the PbTe content increases. The phase diagram of the PbSe–PbTe–Bi2Te3–Bi2Se3 reciprocal system illustrates the phase composition of the alloys after homogenizing at 770 K.