Charge State of Tin Atoms in Ternary Semiconductor Phases of Sn1-xAg2xTe and Sn1-xCu2xTe.

The boundaries of SnTe homogeneity regions in the SnTe-Cu₂Te and SnTe-Ag₂Te systems were determined (~2 mol.% Cu₂(Ag₂)Te). Nonmonotonous character of concentration dependences of unit cell parameter and microhardness within SnTe homogeneity regions caused by interactions between impurity atoms and nonstoichiometric defects was revealed. Mössbauer experiments showed that introducing Ag ₂Te into SnTe results in partial change of tin valence state from Sn²⁺ to Sn⁴⁺. The ratio of the Sn⁴⁺ to Sn²⁺ concentrations increases with increasing Ag₂Te content. Such effect was not observed in Cu₂Te - doped SnTe. The possible causes of different behaviour of Cu₂Te and Ag₂ITe were discussed.