THERMODYNAMIC PROPERTIES AND CRYSTAL STRUCTURES OF NONSTOICHIOMETRIC NIOBIUM SELENIDES NbSex FOR x equals 1. 48-2. 00.

Abstract

Pressure-composition-temperature relations were determined by annealing under controlled selenium vapor pressure in the composition range x equals 1. 48-2. 00. There exist five phases; Nb//2Se//3, 2H(a), 3R, 2H( beta ) and 4H. The 2H(a) and 3R phase are stable over a wide range of nonstoichimetric composition; the 2H( beta ) and 4H phases have a narrow range at x equals 2. 00. The defect structures of 2H(a) and 3R phases were analyzed.