Phase transformation studies of ceramic BaTiO3 using thermo-Raman and dielectric constant measurements

Ferroelectric phase transformation characteristics of ceramic BaTiO3 have been studied by combined thermo-Raman and dielectric measurements. The temperature dependence of Raman bands at 311 and 721 cm(-1) shows that tetragonal to cubic (T-C) phase transformation occurs over a range of temperature. The increase in the bandwidths of these bands indicates that this transformation is an order-disorder transformation. The differential thermo-Raman intensity thermograms show a dip at a temperature corresponding to the maximum rate of phase transformation and this temperature can be defined as phase transformation temperature T-p. The ferroelectric transformation temperature T-m corresponding to the peak in the epsilon(T) obtained from the temperature dependence of dielectric constant is found to coincide with T-p. This indicates that maximum in dielectric constant occurs at the maximum rate of T-C phase transformation. Both T-p and T-m exhibit thermal hysteresis. The Curie temperature T-C obtained from the intersection of tangential of inverse dielectric constant to the temperature axis and is found to be less than T-m and T-p in agreement with O. G. Vendik and S. P. Zubko [J. Appl. Phys. 88, 5343 (2000)] calculations. Thermo-Raman spectroscopy coupled with dielectric constant measurement is shown to be an effective technique to investigate the phase transformation in ferroelectric materials. (C) 2002 American Institute of Physics.