Dielectric relaxation of free charge carriers in some fluorite-type solid solutions

Low-frequency dielectric relaxation was observed in solid solutions Ba1-xThxF2+x and Cd1-xErxF2+x of fluorite type. The relaxation can be satisfactorily described by the Havriliak-Negami formula: epsilon*(f)-epsilon(infinity)=Delta epsilon/{1+[if/f(r)](1-beta)}(1-gamma). The activation energy for relaxation turned to be equal to that for DC-conductivity in the system under study. This suggests that the relaxation is closely related to the ion transport and agrees with the model of a dipole-like behavior of free charge carriers. The relaxation is of strongly non-Debye type and contributes to the high frequency conductivity in the form: sigma=sigma(DC)[1+(f/f(h))(a)] with alpha=beta+gamma-beta gamma. (C) 1998 Elsevier Science B.V. All rights reserved.