Far infrared properties of BaTiO3 ceramics

Far infrared and mid infrared reflectivity measurements have been made at BaTiO3 ceramics at room temperature in the range between 10 mu m and 200 mu m. The Kramers-Kronig analysis and a fitting procedure, based on a four parameter model of the spectrum, determined the infrared active transverse and longitudinal optical modes, their damping factors and the values of dielectric permittivity. Group theory analysis has been done and the number of experimentally observed infrared active modes was compared with the theoretical prediction. The calculated values of the parameters were compared for samples produced with different technology treatment. The high frequency dielectric permittivity (at 10(13) Hz) decreases from 5.13 to 1.88 for the BaTiO3 samples sintered at 1320 degrees C for ten and two hours, respectively. Similarly the change of other parameters provides some information about densification of BaTiO3 ceramics. It was also concluded that infrared optical reflectivity measurements could give reliable results at the boundary cases, when it is difficult to distinguish ifa material has either cubic or tetragonal structure.