Formation of Solid Solutions of New Tungsten Bronze-Type Microwave Dielectric Compounds Ba6-3xR8+2xTi18O54 (R=Nd and Sm, 0≤x≤1)

The formation of solid solutions of microwave dielectric compounds having compositions in the vicinity of Ba3.75-R 9.5Ti18O54 and/or BaO·R 2O3·4TiO2 (R=rare earth) has been investigated. 3BaO·2R 2O3·9TiO2 (Ba6 R 8Ti18O54) solid solutions with the ideal formulae of Ba6-3x R 8+2x Ti18O54 (0.0≤x≤1.0) have been derived on the tie line with the ratio Ti:O=1:3 between perovskite and R 2Ti3O9 based on the new tungsten bronze-type crystal structure with 2×2 perovskitelike unit cells. The type of solid solutions is substitutional with following the relation 3Ba2+2R 3++. Lattice parameters as a function of composition have been determined by the WPPD (whole-powder-pattern decomposition) method.17) The formation range is located at 0.3≤x≤0.7 compositions in the case of R=Sm and 0.0≤x≤0.7 in R=Nd. In the latter case, two kinds of substitutions of the solid solutions are considered.