Products and microwave dielectric properties of ceramics with nominal composition (Ba0.9Ca0.1)(YxB′1/2)O(3x+4.5)/2 (B′ = Nb5+, Ta5+)

The products and microwave dielectric properties of ceramics with nominal composition (Ba0.9Ca0.1)(YxB'(1/2))O(3x+4.5)/2 (B'=Nb5+, Ta5+) are investigated. When x=0.5, i.e. (Ba0.9Ca0.1)(Y1/2B'(1/2))O-3 (B'=Nb5+, Ta5+), the product contains a considerable amount of Y2O3 as well as the main perovskite phase. When x=0.3 the product is single phase, equivalent to Ba(Ca1/9Y3/9 Nb-5/9)O-3 or Ba(Ca1/9Y3/9Ta5/9)O-3. The lattice parameters of these new compounds are smaller than those of Ba(Y1/2Nb1/2)O-3 and Ba(Y1/2Ta1/2)O-3. The relative permittivities (epsilon(r)) of these new compounds are larger than those of Ba(Y1/2B'(1/2))O-3 (B'=Nb5+, Ta5+). The increase in E, of the Nb-system is about 4 times larger than that of the Ta-system. The Qf values of the present ceramics are larger than the Ca-containing perovskite in the (Ba1-xCax)(Mg1/3Ta2/3)O-3 system. The sharp increase Of er in this Study cannot be explained by the Ca2+ rattling ion model at the A-site, which applies to the case of the (Ba1-xCax)(Mg1/3Ta2/3)O-3 system. A new method to explain the increase in epsilon(r) is discussed. (C) 2003 Elsevier Ltd. All rights reserved.