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 $Tp.$ 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.