Transformation of dielectric properties and appearance of relaxation behavior in Pb5(Ge1−xSix)3O11 crystals

The special features of the dielectric properties and conduction of ferroelectric crystals of Pb5(Ge1−xSix)3O11 (0 ≤ x ≤ 0.67) solid solutions were studied. Permittivity anomalies close to the temperatures T1 ≈ 260 K and T2 ≈ 130 K, the appearance of relaxator behavior at x > 0.35, and critical behavior of the concentration dependences of dielectric and pyroelectric characteristics at x1 = 0.35 and x2 = 0.60 were observed and studied. These phenomena were found to be related to the dynamics of charge localization on defects with activation energies of Ua1 ≈ 0.6 eV and Ua2 ≈ 0.23 eV. Relaxator behavior appears when the Curie point lies in the temperature region of thermal charge localization. The concentration dependence features at x1 and x2 are explained by the coincidence of the Curie point and the centers of the temperature regions of charge localization on the Ua1 and Ua2 defect levels, respectively.