Temperature-dependent dielectric, impedance and tunability studies on bismuth zinc niobate ((Bi1.5Zn0.5)(Nb1.5Zn0.5)O7) ceramics

Bi2O3-ZnO-Nb2O5-based pyrochlore ceramics are receiving increasing attention due to their excellent dielectric properties in the microwave frequency range. Site disorder at the pyrochlore A-site is well known for lone pair active cations like Bi3+ and is attributed as the reason for this material's high dielectric constant and tunability. Bismuth zinc niobate ((Bi1.5Zn0.5)(Nb1.5Zn0.5)O7) [BZN] ceramics are prepared by the conventional solid-state reactions. The relative permittivity (ɛr) and the dielectric loss tangent (tan δ) of the BZN ceramics sintered at 1000 °C are found to be around 130 and 0.0004, respectively at a frequency of 1 MHz measured at room temperature. The impedance spectroscopy measurements are conducted at different temperatures to separate grain and grain boundary contributions to the dielectric constant. The tunability of these ceramics is studied under a constant dc bias voltage.