The effect of MgO doped on the microstructural and dielectric properties of (Bi_1.5Zn_0.5)(Ti_1.5Nb_0.5)O₇ ceramics

Abstract

Dense ceramics of the pyrochlore (Bi_1.5Zn_0.5)(Ti_1.5Nb_0.5)O₇ can be prepared at 1100 °C and exhibit a high permittivity (ε_r = 200) and low dielectric loss (tan δ < 1 × 10⁻⁴) at 1 MHz and room temperature. In this study, the effect of MgO addition on the phase evolution, sintering behaviour, microstructures and dielectric properties of (Bi_1.5Zn_0.5)(Ti_1.5Nb_0.5)O₇ (BZTN) ceramics are investigated. The ceramics were sintered in air at temperatures ranging from 850° to 1000 °C. BZTN ceramics with small amount of MgO addition can significantly increase the density and improve the dielectric properties. It is found that MgO doped BZTN ceramics can be sintered at 900 °C to obtain a density higher than 94 % of the theoretical density. Scanning electron microscope (SEM) observations show that the BZTN grain sizes increase with increasing amounts of MgO. No secondary phases in the MgO doped BZTN ceramics were observed using X-ray diffraction (XRD) analysis. A high dielectric constant of 220, a low dielectric loss of 0.02 % and a stable temperature coefficient of capacitance (ΔC/C ∼ ±12 % in the temperature range from −55 to 125 °C) were obtained for 0.5 mol.% MgO-doped BZTN ceramics sintered at 900 °C for 2 h.