FORMATION OF SOLID-SOLUTIONS OF NEW TUNGSTEN BRONZE-TYPE MICROWAVE DIELECTRIC COMPOUNDS N-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-1)(2XTI18O54 (R=ND AND SM, 0)

The formation of solid solutions of microwave dielectric compounds hav ing compositions in the vicinity of Ba3.75R9.5Ti18O54 and/or BaO.R2O3. 4TiO2 (R=rare earth) has been investigated. 3BaO.2R2O3.9TiO2 (Ba6R8Ti1 8O54) solid solutions with the ideal formulae of Ba6-3xR8-2xTi18O54(0. 0 less-than-or-equal-to X less-than-or-equal-to 1.0) have been derived on the tie line with the ratio Ti:O=1:3 between perovskite and R2Ti3O 9 based on the new tungsten bronze-type crystal structure with 2 x 2 p erovskitelike unit cells. The type of solid solutions is substitutiona l with following the relation 3Ba2+ reversible 2 R3+ + square. Lattice parameters as a function of composition have been determined by the W PPD (whole-powder-pattern decomposition) method. 17) The formation ran ge is located at 0.3 less-than-or-equal-to x less-than-or-equal-to 0.7 compositions in the case of R=Sm and 0.0 less-than-or-equal-to x less -than-or-equal-to 0.7 in R=Nd. In the latter case, two kinds of substi tutions of the solid solutions are considered.