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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)O3 (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(Ca1/9Y3/9Nb5/9)O3 or Ba(Ca1/9Y3/9Ta5/9)O3. The lattice parameters of these new compounds are smaller than those of Ba(Y1/2Nb1/2)O3 and Ba(Y1/2Ta1/2)O3. The relative permittivities (ϵr) of these new compounds are larger than those of Ba(Y1/2B′1/2)O3 (B′=Nb5+, Ta5+). The increase in ϵr of the Nb-system is about 4 times larger than that of the Ta-system. The Q f values of the present ceramics are larger than the Ca-containing perovskite in the (Ba1−xCax)(Mg1/3Ta2/3)O3 system. The sharp increase of ϵr 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)O3 system. A new method to explain the increase in ϵr is discussed. [Copyright &y& Elsevier]

The products and microwave dielectric properties of ceramics were investigated which had nominal composition (Ba1−xCax)(B1/2B1/2′)O3 (B3+=Y3+, Nd3+, Gd3+; B′5+=Nb5+, Ta5+). The products versus x relationships of these systems were complex, owing to the small amounts of the third and fourth compounds in a wide range of intermediate x. Dielectric properties of (Ba1−xCax)(Nd1/2Nb1/2)O3, (Ba1−xCax)(Y1/2Nb1/2)O3 and (Ba1−xCax)(Y1/2Ta1/2)O3 systems were evaluated. Relative permittivities (ϵr) of the first system changed linearly with x; however, those of the last two systems increased sharply to have respective peaks at x of 0.2, and then decreased with x. Those sharp increases in ϵr were similar to those reported for (Ba1−xCax)(Mg1/3Ta2/3)O3 and other systems. However, the relative values of the increase in ϵr were different. Plausible mechanisms to explain those differences among systems are discussed by introducing an index of rattling of the Ca2+ ion. [Copyright &y& Elsevier]