THERMODYNAMICS AND VACANCY ORDERING IN TITANIUM - TELLURIUM ALLOYS WITH NIAS TYPE CRYSTAL-STRUCTURES

Tellurium vapor pressures were determined by an isopiestic method for solid titanium - tellurium alloys with NiAs-derivative crystal structu res between 55 and 66.7 at.% Te and between 825 and 1350 K. Activities and partial molar enthalpies of tellurium were derived from them. The results are interpreted in terms of a statistical theoretical model, based on a Cr3S4 type superstructure (with a certain ordering pattern of titanium vacancies) for Ti3Te4. The model curve describing the expe rimental activity data is compatible with the assumption of a continuo us transition from the Cr3S4 type superstructure (at 57.1 at.% Te) thr ough the V5Se8 type superstructure (at 61.5 at.% Te) to the CdI2 struc ture (at 66.7 at.% Te).