Solid Solutions in the Ag2Se-PbSe-Bi2Se3 System

The phase equilibria in the pseudoternary system Ag2Se-PbSe-Bi2Se3 have been studied using differential thermal analysis, x-ray diffraction, and microhardness measurements. The results have been used to construct the T-x phase diagram along the AgBiSe2-PbSe join and the 900-K section of the ternary phase diagram. The AgBiSe2-PbSe system contains a continuous series of cubic solid solutions with the NaCl structure. Their lattice parameter is an almost linear function of composition (a = 5.822-6.125 angstrom). The formation of the solid solutions stabilizes the high-temperature phase of AgBiSe2: PbSe dissolution in this compound markedly reduces its polymorphic transformation temperature (590 K). down to room temperature at 10 mol % PbSe. In the Ag2Se-PbSe-Bi2Se3 system, the gamma-phase exists in a broad re-ion around the AgBiSe2-PbSe pseudobinary join.