Effect of sintering parameters on the microstructure and microwave dielectric properties of Ba(Zn_1/3Nb_2/3)O₃–ZnNb₂O₆ Ceramics

Ba(Zn_1/3Nb_2/3)O₃–ZnNb₂O₆(BZNZ) composite ceramics were fabricated by conventional solid solution processing. After optimizing the composition, the effects of the sintering parameters, such as the heating rate, the soaking time, and the cooling rate on densities, microstructure, and microwave dielectric properties were investigated using orthogonal experimental design method. The results show that with increasing the content of Ba(Zn_1/3Nb_2/3)O₃, the ε _r increases, while the Q × f value increases first, then decreases, and τ _f shifts to the negative value. The BZNZ ceramics with composition of 0.3Ba(Zn_1/3Nb_2/3)O₃–0.7ZnNb₂O₆ show the optimal dielectric properties. The results of orthogonal experimental design show that sintering parameters play an important role in the microstructure and dielectric properties. The ceramics show obvious duplex-grain structure. The importance sequence of the sintering parameters is: cooling rate > heating rate > soaking time. The sintering parameters were optimized, with 0.3Ba(Zn_1/3Nb_2/3)O₃–0.7ZnNb₂O₆ ceramic sintered at a heating rate of 2 °C/min, soaking time of 8 h, and cooling in the air. Samples have the excellent dielectric properties: ε_r = 32.75, Q × f = 34,100, and τ _f  = −10.2 ppm/°C.