Crystal Structure and Microwave Dielectric Properties of Aeschynite-Type R(W0.5Ti1.5)O6 (R = Nd, Sm, Eu, Gd and Dy) Ceramics

Abstract

The microwave dielectric properties and crystal structure of aeschynite-type structured R(W0.5Ti1.5)O6 (R=Nd, Sm, Eu, Gd and Dy) ceramics were characterized to investigate a microwave dielectric ceramic that is suitable for use in the base station. A single phase of R(W0.5Ti1.5)O6 ceramics was obtained; it was recognized that the lattice parameters of the ceramics vary linearly, depending on the ionic radii of the R ions. The dielectric constants of R(W0.5Ti1.5)O6 ceramics were also related to the ionic radii of the R ions and changed linearly with the ionic radii. From the result of crystal structure analysis, a decrease in the covalency of the (W,Ti)-O bond was observed with increasing the ionic radii of the R ions; these variations in covalency corresponded to the linear increases in the dielectric constants of the R(W0.5Ti1.5)O6 ceramics. The Q·f and τf values significantly depended on the R ions; the highest Q·f value with a near zero τf value was obtained for the Sm(W0.5Ti1.5)O6 ceramic (Q·f =35000 GHz and τf =-0.7 ppm/°C).