Preparations of ZnWO₄ based ceramics with near-zero resonant frequency temperature coefficient for microstrip antenna application

(1-x)ZnWO₄-xBa₃(VO₄)₂ (x = 0.45-0.55), (1-x)ZnWO₄-xTiO₂ (x = 0.06-0.08) complex phase ceramics were prepared by secondary sintering process, and the phase structure, microstructure morphology and microwave dielectric properties of complex phase ceramics were systematically studied. Ba₃(VO₄)₂ and TiO₂ were used as additives to adjust the resonant frequency temperature coefficient of ceramics to be close to zero. The results show that the Ba₃(VO₄)₂ phase is decomposed at high temperature. The compounding of TiO₂ can change the microstructure morphology of ceramics and effectively regulate the τ_f of ceramics. With the increase of TiO₂ content, the grain size of ZnWO₄(ZW)-TiO₂ gradually decreased, the dielectric constant ε_r gradually increased, the Q×f value decreased to a certain extent, and the τ_f value gradually approached zero. When the TiO₂ content x = 0.07, the microwave dielectric properties of ZW-TiO₂ complex ceramics were the best under the condition of 1050 °C for 2 h: ε_r = 19.21, Q×f = 65721 GHz, τ_f = −2 ppm/^°C. On this basis, a microstrip patch antenna with a working frequency of 2.45 GHz is designed. The simulation results show that when the resonant frequency is 2.45 GHz, the S11 parameter is −34.77 dB, the maximum gain is 3.3 dB, and the radiation efficiency is 98.77%.