Low-temperature sintering microwave dielectrics using CuO-doped Zn(Nb _0.95Ta_0.05)₂O₆ ceramics

The effect of CuO additions on the sintering behavior and microwave dielectric properties of Zn(Nb_0.95Ta_0.05) ₂O₆ ceramic and its chemical compatibility with Ag have been investigated. The CuO addition can effectively lower the sintering temperature of Zn(Nb_0.95Ta_0.05)₂O₆ ceramics to 930°C due to the liquid phase effect. The (ZnCu ₂)(Nb_0.95Ta_0.05)₂O₈ liquid phase will be separated out and exists as a crystalline phase in the final stage. In addition to the (ZnCu₂)(Nb_0.95Ta _0.05)₂O₈ liquid phase, a second phase Zn ₃(Nb_0.95Ta_0.05)₂O₈ is also detected during the synthesis of specimen. Both phases show a relatively low ε_r and Q × f values compared with that of simple Zn(Nb_0.95Ta_0.05)₂O₆. The Q × f value is a function of the sintering temperature and the amount of CuO addition. With 4.5 wt% CuO addition, it varies from 8500 to 77 200 GHz as the sintering temperature increases from 840°to 930°C for 2 h. For low-firing multilayer applications, a combination of dielectric properties with an ε_r of ∼22.87, a Q × f of ∼77 200 GHz, and a τ_f of ∼-70.8 ppm/°C can be achieved for 4.5 wt% CuO-doped Zn(Nb_0.95Ta_0.05)₂O₆ ceramic sintered at 930°C for 2 h.