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)Ba3(ZnNb2)O9-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-x)1/3(Nb1-xWx)2/3O3, which underwent an order–disorder transition at 1410°C, ∼35° higher than pure Ba(Zn1/3Nb2/3)O3. 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°C. The tungstate-containing solid solutions can be sintered to a high density at 1390°C, and the resultant ordered ceramics exhibit some of the highest microwave dielectric Q factors (Q×f=1 18 000 at 8 GHz) reported for a niobate-based perovskite.