Infrared reflection spectra of Ba6−3xSm8+2xTi18O54 (x=0.5, 0.67, and 0.75) microwave dielectric ceramics

Abstract

Infrared reflection spectra of the tungsten bronze-type Ba6−3xSm8+2xTi18O54 (x=0.5, 0.67, and 0.75) ceramics were measured and analyzed by a combined method using Kramers-Kroning relation and the classical oscillator model, and the selection rules and vibration modes of the tungsten bronze-type structure were investigated by a detailed group theory analysis. Microwave dielectric properties were calculated using the dispersion parameters obtained by the classical oscillator model. The error in reflectance due to the random scattering on sample surfaces indicated obvious effect on the calculated dielectric constant, but only slightly influenced the calculated Qf, and therefore, the present analysis provided a reasonable means to predict the intrinsic microwave dielectric loss. The predicted intrinsic Qf values (>30000GHz) were much higher than the experimental ones (∼10000GHz), and this suggested the great potential of significant improvement of Qf value in Ba6−3xSm8+2xTi18O54 ceramics by controlling the extrinsic dielectric loss.