The PbSb2Se4–Pb5Bi6Se14 section of the Sb2Se3–PbSe–Bi2Se3 quasi-ternary system

Abstract

The PbSb2Se4–Pb5Bi6Se14 section of the Sb2Se3–PbSe–Bi2Se3 quasi-ternary system was studied by integrated physicochemical analysis methods, and the state diagram of this section was constructed. The PbSb2Se4–Pb5Bi6Se14 section was found to be a partially quasi-binary section of the Sb2Se3–PbSe–Bi2Se3 quasi-ternary system. A region of solid solutions based on PbSb2Se4 at room temperature was detected at 10 mol % Pb5Bi6Se14. At a ratio between the initial components of 1: 1, congruently melting quaternary compound Pb6Sb2Bi6Se18 forms. Its single crystals were produced by the method of chemical transport reactions. Pb6Sb2Bi6Se18 crystallizes in the rhombic system with the unit cell parameters a = 14.43 A, b = 21.42 A, c = 3.90 A, V0 = 1205 A3, Z = 4, and space group Pnnm. The thermodynamic functions of Pb6Sb2Bi6Se18 were calculated: the standard entropy S2980 = 1472.8 J mol–1 K–1, the enthalpy ΔH2980 =–1215.8 kJ mol–1, and the Gibbs free energy of formation ΔG2980 =–1193.6 kJ mol–1.