Dielectric Properties and Microstructures of Low-Temperature-Sintered BaTiO3-Based Ceramics with CuBi2O4 Sintering Aid

Abstract

The low-temperature sintering of BaTiO3 (BT) ceramics was investigated by conventional ceramics processing using a CuBi2O4 sintering aid, and the dielectric properties and microstructures of the ceramics were examined. BT powders without CuBi2O4 could not be fully densified at sintering temperatures lower than 1300 °C. However, the addition of CuBi2O4 markedly enhanced the sinterbility of BT powders, and the sintering temperature decreased from 1300 to 920 °C. This may be due to the promotion of liquid-phase sintering. 6.0 wt % CuBi2O4-added BT ceramics sintered at 920 °C exhibited a high density of 5.95 g/cm3. Moreover, to obtain dielectric ceramics with a stable temperature coefficient of capacitance, the effects of ZnO addition on the dielectric properties and microstructures of low-temperature-sintered BT ceramics with a CuBi2O4 sintering aid were also studied. It was found that the addition of ZnO was very effective for improving the temperature coefficient of capacitance and reducing the dielectric loss of the low-temperature-sintered specimens. This is attributable to the microstructural change involving the formation of a core-shell structure, as shown by transmission electron microscopy and X-ray energy-dispersive spectrometry (TEM–EDS). Therefore, a high dielectric constant of 1900, a low dielectric loss of 0.6% and a stable temperature coefficient of capacitance (X7R EIA standard of ΔC/C25 °C=±15% in the temperature range from -55 to +125 °C) were obtained for 1.0 wt % ZnO-added BT ceramics with 6.0 wt % CuBi2O4 sintered at 930 °C for 2 h.