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)O-3 - (1-x)Ba(Co1/3Nb2/3)O-3 system were produced by the mixed oxide route. Sintering temperatures of 1300-1500 degreesC with cooling rates of 3-180 degreesC/h were used. Sintered densities of less than or equal to 95% were achieved. A second phase deficient in Co and Zn was detected. Slow cooling after sintering, down to 900 degreesC, induced B-site ordering which increased the dielectric Q values. Compositions near to 0.6[Ba(Zn1/3Nb2/3)O-3] - 0.4[Ba(Co1/3Nb2/3)O-3] exhibited zero temperature dependence of resonant frequency (tau(f) similar to 0). The presence of the second phase (Zn/Co deficient) improved the dielectric properties. Ceramics of optimum composition, having x similar to 0.6, have excellent electrical properties, (Q value similar to 43,000 at 2 GHz, relative permittivity epsilon(r) similar to 35.5 and tau(f) tunable through zero). The material will offer a new design option for filter engineers in the development of 3G and other similar telecommunication systems. (C) 2003 Elsevier Ltd. All rights reserved.