Nikolaienko A. Influence of irradiation on transformation of modulated structures in ternary chalcogenide ferroelectrics

The thesis is devoted to the study of regularities of changes in the crystal structure and electrical conductivity during the formation and decay of modulated structures in ternary chalcogenide ferroelectrics TlInS2 and Ag3AsS3, also to determine the effect of X-ray and optical irradiation on the parameters of such processes. By X-ray three circles diffractometry it was revealed that for certain absorbed dose (2.9 kGy), the incommensurate phase was formed at room temperature, whereas for the unirradiated samples the formation of incommensurate phase satellites with qi(±δ;0;±0.25) (δ=0,045±0,006) with low intensity was detected at temperatures of 238 K–240 K, which exceed the known from the literature temperature of phase transition by 24 K–26 K. The changes in the shape and relative intensity of the satellites upon irradiation indicate about the formation of several waves of static atomic displacements with different values of the disparity parameter δ = 0.02 – 0.17 and the formation of waves of the concentration of atoms in the direction of displacement waves.