Formation of Solid Solutions of New Tungsten Bronze-Type Microwave Dielectric Compounds Ba_6-3xR_8+2xTi₁₈O₅₄ (R=Nd and Sm, 0≤x≤1)

Abstract

The formation of solid solutions of microwave dielectric compounds having compositions in the vicinity of Ba 3.75 - R 9.5 Ti 18 O 54 and/or BaO· R 2 O 3 ·4TiO 2 ( R =rare earth) has been investigated. 3BaO·2 R 2 O 3 ·9TiO 2 (Ba 6 R 8 Ti 18 O 54 ) solid solutions with the ideal formulae of Ba 6-3 x R 8+2 x Ti 18 O 54 (0.0≤ x ≤1.0) have been derived on the tie line with the ratio Ti:O=1:3 between perovskite and R 2 Ti 3 O 9 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 3Ba 2+ \rightleftarrows2 R 3+ +\Box. 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.