Influence of Non-Stoichiometry on the Structure and Properties of Ba(Zn1/3Nb2/3)O3 Microwave Dielectrics. IV. Tuning ϗf and the Part Size Dependence of Q Ê f

High Q ceramics of Ba3W2O9 (BW)-substituted Ba(Zn1/3Nb2/3) O3 (BZN) were prepared with a zero τf through the partial substitution of Zn by Ni and Co. The small concentrations of B-site vacancies introduced by the substitution of BW accelerated the kinetics and stability of the cation ordering and lowered the sintering temperature. Dense, zero τzf, ordered solid solutions such as 0.99Ba(Zn0.3Co0.7)1/3Nb2/ 3O3–0.01BW with εr=34.4 and Q×f=82 000 at ~8 GHz could be obtained after sintering at 1380°C for 5 h and annealing at 1300°C for 24 h. Partially ordered ceramics in the Zn/Co and Zn/Ni solid solutions show a large gradient in the ordering throughout the pellets, which produces a resonant frequency dependence of their Q×f value. The ordering gradient is associated with the increased constraints on the growth of the 1:2 ordered structure within the interior of larger and thicker pellets and can be minimized by extended annealing. Comments Copyright The American Ceramic Society. Reprinted from Journal of the American Ceramic Society, Volume 89, Issue 7, July 2006, pages 2271-2278. This journal article is available at ScholarlyCommons: http://repository.upenn.edu/mse_papers/117 Influence of Non-Stoichiometry on the Structure and Properties of Ba(Zn1/3Nb2/3)O3 Microwave Dielectrics. IV. Tuning sf and the Part Size Dependence of Q f Hui Wu and Peter K. Davies Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6272 HighQ ceramics of Ba3W2O9 (BW)-substituted Ba(Zn1/3Nb2/3) O3 (BZN) were prepared with a zero sf through the partial substitution of Zn by Ni and Co. The small concentrations of B-site vacancies introduced by the substitution of BW accelerated the kinetics and stability of the cation ordering and lowered the sintering temperature. Dense, zero sf, ordered solid solutions such as 0.99Ba(Zn0.3Co0.7)1/3Nb2/3O3–0.01BW with er5 34.4 and Q f5 82 000 at B8 GHz could be obtained after sintering at 13801C for 5 h and annealing at 13001C for 24 h. Partially ordered ceramics in the Zn/Co and Zn/Ni solid solutions show a large gradient in the ordering throughout the pellets, which produces a resonant frequency dependence of their Q f value. The ordering gradient is associated with the increased constraints on the growth of the 1:2 ordered structure within the interior of larger and thicker pellets and can be minimized by extended annealing.