Nonisothermal relaxation and electromigration in single crystals of Ca3Ga2Ge4O14

The photoconductivity and electrical conductivity, the thermally stimulated polarization and depolarization currents, the permittivity, and the dielectric losses of noncentrosymmetric Ca₃Ga₂Ge₄O₁₄ crystals of a structural type of trigonal calcium gallogermanate (CGG) have been studied for the first time in the temperature interval 100–700 K in air and in vacuum. The features of the temperature behavior of CGG are associated, in particular, with the effect of electrically active defects and partial disordering of the cation sublattice of the crystal structure, which generates polar formations (dipoles) of several kinds. Certain parameters of the electromigration and of the electrically active defects that cause charge-relaxation and polarization effects are determined. It is concluded that dipole relaxation in CGG makes it a new representative of a class of materials in which reorientation of the dipoles as a system of mobile local distortions of the structure has a substantial effect on the physical properties. Fiz. Tverd. Tela (St. Petersburg) 39, 871–876 (May 1997)