THERMODYNAMIC BEHAVIOR OF THE SN-TE, PB-TE, SN-SE AND PB-SE MELTS ACCORDING TO THE ASSOCIATED MODEL

The regular associated treatment has been applied to the four systems in order to check if there is a correlation between them. The model shows that the Sn-Se, Pb-Se, Sn-Te and Pb-Te liquid phases exhibit quantitatively the same thermodynamic behavior due to short-range order corresponding to the compositions of the congruently melting equiatomic compounds. In the case of the Sn-Se melts, the existence of a second congruently melting compound, namely SnSe2, has no influence on the thermodynamic properties of the melt. The selenium-based alloys are more associated than the tellurium-based alloys. The main difference between them is the strongly positive (selenium) and negative (tellurium) values of the standard entropy of formation of the associates.