Radiation defects and phase transition in some glycine-containing ferroelectrics

The influence of radiation defects on the thermodynamic properties in glycine-containing ferroelectrics (TGSe, DTGSe) was studied in the three regions, small (D < 1 MR), middle (1 MR < D < 5 MR) and large (D > 5 MR) doses of irradiation, by calorimetric experiments. The systematic change of Landau free energy coefficients was detected for the system TGSe-DTGSe and the order of phase transition was changed from the first to the second by small radiation defects concentration in DTGSe crystal. The dose dependence of the basic phase transition parameters was revealed and compared with the result of microscopic theory of defected crystals phase transitions for small defect concentration (independent defects approximation).