Far infrared spectroscopy of Sr1-xBaxTiO3 (0.01 <= x <= 0.2) ceramics

We report on lattice dynamics and far infrared dielectric response of Sr1-xBaxTiO3 ceramics with small concentration of Ba (0.01 <= x <= 0.2). Reflectivity spectra were obtained on cooling down to 5 K by Fourier transform interferometer in the 25-650 cm(-1) frequency range and by coherent-source submillimetre technique in the 30-40 cm(-1) range and fitted by the factorized model of the dielectric function. Fitted permittivity was compared with the dielectric data measured in the 10(2)-10(6) Hz frequency range. Splitting of the soft TO1 phonon into E and A(I) components, indicating the jerroelectric transition, was observed for x >= 0.05. In addition to the soft mode dispersion, low-frequency dielectric relaxation Was observed in the vicinity of the permittivity maximum, indicating a crossover into order-disorder regime with relaxorferroelectric features.