Influence of non-stoichiometry on the structure and properties of Ba(Zn1/3Nb2/3)O3 microwave dielectrics:: I.: Substitution of Ba3W2O9

A narrow region of Zn-vacancy-containing cubic perovskites was formed in the (1-x) Ba-3(ZnNb2) O-9-(x) Ba3W2O9 system up to 2 mol% substitution (x = 0.02). The introduction of cation vacancies enhanced the stability of the 1: 2 B-site ordered form of the structure, Ba(Zn1-x rectangle(x))(1/3)(Nb1-xWx)(2/3)O-3, which underwent an order-disorder transition at 1410 degrees C, similar to 35 degrees higher than pure Ba(Zn1/3Nb2/3)O-3. The Zn vacancies also accelerated the kinetics of the ordering reaction, and samples with x = 0.006 comprised large ordered domains with a high lattice distortion (c/a = 1.226) after a 12 h anneal at 1300 degrees C. The tungstate-containing solid solutions can be sintered to a high density at 1390 degrees C, and the resultant ordered ceramics exhibit some of the highest microwave dielectric Q factors (Q x f = 118000 at 8 GHz) reported for a niobate-based perovskite.