Microwave quality factor improved by ordering of Ba and rare-earth on the tungsten bronze-type Ba/sub 6-3x/R/sub 8+2x/Ti/sub 18/O/sub 54/ (R=La, Nd and Sm) solid solutions

Microwave dielectric properties of the tungsten bronze-type Ba/sub 6-3x/R/sub 8+2x/Ti/sub 18/O/sub 54/ (R=La, Nd and Sm) solid solutions are investigated as a function of the composition x. The quality factor which is the inverse of the dielectric loss changes non-linearly as a function of the composition, though the dielectric constant and the temperature factor of the resonant frequency changes linearly. The distribution of large cations in the rhombic sites and the pentagonal sites in the crystal structure leads to this non-linearity. When the rare earth ions and Ba ions occupy separately the rhombic sites and pentagonal sites, the quality factor is the highest. The internal strain is reduced at x=2/3, which is confirmed from FWHM by X-ray diffraction experiments.