Dielectric loss and damping constants of lattice vibrations in Ba(Mg1/3,Ta2/3)O3 ceramics

Far-infrared reflectivity spectra for Ba(Mg1/3,Ta2/3)O3 ceramics (prepared from high quality oxide reagents) sintered at 1600 °C for 4 and 50 h were measured at room temperature, to determine eigen frequencies and damping constants of lattice vibration in order to understand why the Q·f value at microwave frequency was improved by sintering time. The observed reflectivity spectra were fitted to 16 IR active modes predicted by factor group analysis in order to estimate the fitting parameters. Differences in reflectivity and damping constants were confirmed between the two samples by observation of the measurement spectra and their spectrum fitting. The fitting parameters were used to simulate dielectric loss at low frequency. Results of the simulation suggested a contribution of 3rd, 4th and 5th vibration modes to dielectric loss at low frequency.