MEASUREMENTS OF HIGH-TEMPERATURE HEAT-CONTENT OF THE II-VI AND IV-VI (II-ZN, CD IV-SN, PB VI-SE, TE) COMPOUNDS

High temperature heat contents of the II-VI and IV-VI compounds (II: Zn, Cd IV: Sn, Pb VI:Se, Te) were measured over the temperature range of 700-1550 K using a drop calorimeter. The heat of alpha-beta transformation of SnSe was 1.1+/-0.1 kJ/mol at 788+/-2 K, and the heat of fusion of CdSe, CdTe, SnSe, PbSe, SnTe and PbTe were 44.8+/-0.2, 43.5+/-0.3, 35.5+/-0.4, 42.3+/-0.4, 39.5+/-0.3 and 47.6+/-0.4 kJ/mol, respectively, at the corresponding melting points of 1521+/-3, 1373+/-3, 1149+/-2, 1351+/-2, 1080+/-3 and 1209+/-2 K. The heat contents and heat capacity equations were derived using the Shomate function for the solid compounds and the least square method for liquid phases. Based on the third law method, the Gibbs free energies of formation were determined form the obtained heat capacity data.