Microwave properties of Ba(Zn1/3Ta2/3)O3 dielectric resonators

Ba(Zn1/3Ta2/3)O3 (BZT) dielectric resonators were prepared by solid-state reaction. The starting materials were BaCO3, ZnO, and Ta2O5 powders with high purity. The double calcined BZT pellets were sintered in air at temperatures of 1575, 1600, 1625, and 1650 °C for 4 h. The X-ray diffraction data allowed the study of the unit cell distortion degree and the presence of the secondary phases. A long-range order with a 2:1 ratio of Ta and Zn cations on the octahedral positions of the perovskite structure was observed with the increase of the sintering temperature. The dielectric constant of BZT resonators measured around 6 GHz was between 26 and 28. High values of Q × f product (120 THz) were obtained for BZT resonators sintered at 1650 °C/4 h. The temperature coefficient of the resonance frequency exhibits positive values less than 6 ppm/°C. The achieved dielectric parameters recommend BZT dielectric resonators for microwave and millimeter wave applications.

Research highlights▶ Ba(Zn1/3Ta2/3)O3 dielectric resonators with bulk densities up to 95% were obtained by solid-state reaction. ▶ The morpho-structural results obtained by using XRD and SEM were correlated with the microwave dielectric properties. ▶ The temperature coefficient of the dielectric permittivity τɛ was estimated to be −37 ppm/°C by measurements at 1 MHz. ▶ The temperature coefficient of the resonance frequency τf ∼ 6 ppm/°C measured around 6 GHz is in a good agreement with the value estimated from temperature dependence of the capacitance at low frequency. ▶ BZT resonators with dielectric constant around 28 and a Q × f product up to 120,000 GHz were achieved.