Phase equilibria in the La - Mo - Se system at in the vicinity of and

Abstract

Phase relations prevalent in the La - Mo - Se system at in the vicinity of the ternary (Chevrel) phase and of the binary phase, have been established. Characteristic features of this system are as follows: (i) Two isostructural, but mutually immiscible, solid solutions covering considerable compositional intervals exist. One of them, defined as La-intercalated , spreads over a triangular surface, with its origin at the binary and developing into the ternary system, as far as La. One edge of this triangle points towards the isostructural ternary phase . The second three-component solid solution is based on the Chevrel-type phase and takes the shape of a rectangular surface about 2 at% La wide, with 6.67 at% La as the mean value. The domain runs along the line , from x = 0 (40 at% Mo), characteristic of the exact stoichiometry 1:6:8, to x = 0.75 (45 at% Mo). (ii) The continuous solid solution of the type , expected to occur between the binary and the ternary , is absent. The domains of both solid solutions have been established using x-ray powder diffractometry and the evolution of the critical temperatures characteristic for each of the phases.