EFFECT OF A DEVIATION FROM STOICHIOMETRY ON THE MOSSBAUER PARAMETERS OF SN0.8GE0.2TE DURING THE PHASE-TRANSITION

The system of solid solutions (Sn//0//. //8Ge//0//. //2)//1// minus //y Te//y with the values of y equals 0. 499; 0. 505; 0. 510 is investigated by means of the Mossbauer effect on the **1**1**9Sn nucleus within the temperature range 160 to 300 K. The effective Debye temperature and mean-square displacements of tin atoms from equilibrium are calculated. In the region of phase transition (about 200 K) fractures on the temperature dependencies of the isomer shift and Debye temperature are observed, while no anomalies of the Mossbauer effect probability are noticed. No quadrupole interaction is observed with the symmetry decrease in the lattice. A correlation between the isomer shift and interatomic distance is revealed. The ionicity of the chemical bond in the system Sn//xGe//1// minus //xTe is approximately equals 54 percent when x equals 0. 9, and about 40 percent when x equals 0. 1.