Study of dielectric relaxation in Na-doped Bi-Pb-Sr-Ca-Cu-O glasses

In the present study a new glass system of the composition Bi2Pb0.5Sr2Ca2{Cu3-xNax}O-y with x = 0, 0.1, 0.2 and 0.3 was prepared. The system was limited to this range because compositions with other, x, crystallize during quenching of the liquid material. Measurements of dielectric permittivity and loss in the frequency range 0.1 to 10(2) kHz and in the temperature range 300 to 650 K were made. It was evident that these glasses could be considered electronic glasses, based on a de charging current experiment. The effect of increasing Na doping reduces the probability of phonon assisted quantum mechanical tunneling effects. However, the thermal activated relaxation mechanism dominates the observed relaxation behavior. Distribution of relaxation processes was also studied, and a single process was adequate to describe the present experimental data. (C) 1998 Elsevier Science B.V. All rights reserved.