P-T-X phase equilibrium and vapor pressure scanning of non-stoichiometry in CdTe

Total vapor pressure was measured for all the three-phase equilibria in the Cd-Te system. P-T and T-X projections of the diagram were constructed. Results of the vapor pressure scanning of the CdTe solidus surface are reported. Tellurium non-stoichiometry is found to be up to (0.5-13) x 10(-3) at% at temperatures 945 to 1360 K while the cadmium non-stoichiometry is (0.1-4) x 10(-3) at% in the temperature range 695 to 1223 K. Position of the congruent sublimation curve S = V in the P-T-X phase space is discussed and some specifics of the solidus surface are outlined. The maximum congruent sublimation temperature was found to be 1324 K, 41 K lower than the maximum melting point of CdTe. Geometrical analysis of the phase equilibrium in the melting region of CdTe as well as compositions of the crystal, liquid and vapor are presented. Partial molar enthalpies and entropies of the component elements are deduced for CdTe.