Site occupancy of Bi ions and microwave dielectric properties in Ba6-3xNd8+2xTi18O54 solid solutions

The tungstenbronze-type like Ba-6..3x R8 + 2x Ti18O54 (R = rare earth) solid solutions have excellent microwave dielectric properties. In particular. Nd-system materials have high dielectric constant (epsilon(1)) around 80 and high quality factor (Q (.) f) near 10000 GHz. However. the temperature coefficients of the resonant frequency, tau(1), is very poor, 63 ppm degreesC (1) for use as practical microwave material. We have investigated the effects of substituting Bi ions in Ba-6..3x R8 + 2x Ti18O54 (x =2/3) solid solutions in terms of the lattice parameters. and phase structures. It seems that until gamma = 0.05. Bi ions substituted for Ba ions. Thereafter. Bi ions substituted for Nd ions from gamma = 0.05 to 0.3. As gamma increased, the dielectric constant, epsilon(1), increased and the quality factor, Q (.) f, decreased. The temperature coefficients of the resonant frequency, tau(1), improved to 17 ppm degreesC (- 1) at gamma = 0.15. (C) 2002 Published by Elsevier Science B.V.