Dielectric Relaxation and Thermal Stimulated Current in (K3/4Bi1/4)(Zn1/6Nb5/6)O3and Its Solid Solutions

Abstract

Dielectric properties of (K_3/4Bi_1/4)(Zn_1/6Nb_5/6)O₃ and its solid solutions with perovskite structure are studied in the frequency range from 100 Hz to 4 GHz, at temperatures ranging from -100°C to 250°C. The dielectric relaxations are found on the single crystal of (K_3/4Bi_1/4)(Zn_1/6Nb_5/6)O₃ as well as on the ceramics in a temperature region below room temperature. The region is shifted in the direction of lower temperatures by substituting the Bi ions with La ions. Neither dielectric nonlinearity nor structural change is observed in the region of dielectric relaxation. The relaxation seems to arise from the thermal motion of ions over potential barriers which are produced in the crystal by disordered arrangement of ions with different chemical valencies. The existence of the potential barriers is also confirmed by observing thermally stimulated current. The activation energy of potential barrier is estimated to be about 0.44 eV for (K_3/4Bi_1/4)(Zn_1/6Nb_5/6)O₃.