Volume properties and peculiarities of melt structure in A4+-Te systems (A4+-Ge, Sn, Pb)

The density of melts in the systems A4+-Te has been investigated and its isotherms at the melting points of A4+-Te compounds in the systems Sn-Te and Pb-Te and at the melting point of germanium in the system Ge-Te are plotted. Excess mole and partial mole volumes and coefficients of volumetric expansion are calculated. It is shown that thermodynamic properties in the systems Sn-Te and Pb-Te can be described on the basis of the theory of associative equilibrium in the assumption of existence of the only associate SnTe(PbTe) and in the system Ge-Te in the assumption of existence of two associates GeTe and GeTe2, which is related to simultaneous effect of two factors: chemical and geometric one