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

Abstract

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 Tp. The ferroelectric transformation temperature Tm corresponding to the peak in the ε(T) obtained from the temperature dependence of dielectric constant is found to coincide with Tp. This indicates that maximum in dielectric constant occurs at the maximum rate of T–C phase transformation. Both Tp and Tm exhibit thermal hysteresis. The Curie temperature TC obtained from the intersection of tangential of inverse dielectric constant to the temperature axis and is found to be less than Tm and Tp 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.