Microstructure and dielectric properties of Ba(Zn_1/3Nb_2/3)O₃ - ZnNb₂O₆ composite ceramics

Ba(Zn_1/3Nb_2/3)O₃ - ZnNb₂O₆ (BZNZ) ceramics were fabricated via a conventional electric ceramic process. The effect of Ba(Zn_1/3Nb_2/3)O₃ (BZN) on the microstructure and dielectric properties of BZNZ ceramics was investigated. The results show that the introduction of BZN increases the sintering temperature of BZNZ ceramics. A phase of BaNb_3.6O₁₀ appears in the ceramics besides ZnNb₂O₆ and Zn₃Nb₂O₈. The microwave dielectric properties of the BZNZ ceramics were measured. The dielectric constant increases, the value of Q×f firstly increases and then decreases and the temperature coefficient of resonance frequency τ_f shifts to a positive value when the content of BZN increases. The ceramic with the BZN content of 30% (in mole) has the optimal dielectric properties, i.e., ε_r=30.76, Q×f=29600 GHz, tan δ=1.98×10^-4, and τ_f=-2.34×10^-6/°C.