Development of low cost, high performance Ba(Zn1/3Nb2/3O3) based materials for microwave resonator applications

Solid solutions of the (x)Ba(Zn1/3Nb2/3)O3 – (1-x)Ba(Co1/3Nb2/3)O3 system were produced by the mixed oxide route. Sintering temperatures of 1300–1500 °C with cooling rates of 3–180 °C/h were used. Sintered densities of ⩽95% were achieved. A second phase deficient in Co and Zn was detected. Slow cooling after sintering, down to 900 °C, induced B-site ordering which increased the dielectric Q values. Compositions near to 0.6[Ba(Zn1/3Nb2/3)O3] – 0.4[Ba(Co1/3Nb2/3)O3] exhibited zero temperature dependence of resonant frequency (τf ∼0). The presence of the second phase (Zn/Co deficient) improved the dielectric properties. Ceramics of optimum composition, having x∼0.6, have excellent electrical properties, (Q value ∼43,000 at 2 GHz, relative permittivity εr ∼35.5 and τf tunable through zero). The material will offer a new design option for filter engineers in the development of 3G and other similar telecommunication systems.