Dielectric Relaxation and Microwave Dielectric Properties of Bi₂O₃–ZnO–Ta₂O₅ Ceramics

The permittivity of two primary phases within the Bi₂O₃–ZnO–Ta₂O₅ system was measured from 100 Hz to approximately 8.7 GHz. A cubic pyrochlore (Bi_3/2Zn_1/2)(Zn_1/2Ta_3/2)O₇ phase (a phase) exhibited a dielectric constant of 71 at low frequency which decreased to 64 at approximately 10 GHz. A lower symmetry zirconolite Bi2(Zn_1/3Ta_2/3)₂O₇ phase (β phase) was also measured and had a frequency independent dielectric constant of 60. The temperature dependence of the capacitance (τ_C), measured from −55 to 120 °C, was 78 ppm/°C for the β phase and nonlinear for the α phase having no unique slope. The primary difference in dielectric properties between these two phases was a low-temperature relaxation of the α phase, which is modeled as a basic Debye-type relaxation.