Effect of Al2O3 addition on microwave dielectric properties of BaCo0.194Zn0.116Nb0.69O3 ceramics

This study investigates the effects of Al2O3 addition on sintering, microstructures, phase formation and the microwave dielectric properties of BaCo0.194Zn0.116Nb0.69O3 (BCZN) ceramics prepared by the conventional solidstate route. Addition of low alumina content was found to effectively improve the Q×f value of BCZN ceramics. Addition of an appropriate amount of Al2O3 was found beneficial to the growth and uniformity of the ceramic grain, significantly improving the quality factor of BCZN ceramics. However, the performance of the ceramics deteriorated when an excessive secondary phase, inhomogeneous grain of small size and larger porosity were generated from the BCZN ceramic doped with excessive alumina. An optimum Q × f of 61056 GHz (f = 7.44 GHz) was obtained for the BCZN ceramic doped with 1 wt. % Al2O3 addition sintered at 1350°C for 3 h, which is markedly better than that of pure BCZN ceramic sintered at 1300°C for 3 h (13650 GHz, f = 7.02 GHz).