Effect of Sn doping on the phase transformation properties of ferroelectric BaTiO3

Thermo-Raman and dielectric constant measurements were carried out on the samples Ba(SnxTi1-x)O-3, 0 < x < 0.12 simultaneously by coupling a Raman spectrometer with an LCR meter. The differential thermo-Raman intensity (DTRI) thermogram obtained from the Raman intensity revealed a range of temperature for the tetragonal to cubic phase transformation. The phase transformation temperature T-p obtained from the DTRI thermogram was found to be equal to the ferroelectric transformation temperature T-m, obtained from the maximum of the dielectric constant. Both T-p and T-m decreased almost linearly with increasing Sn concentrations. The Curie temperature T-c, Curie-Weiss constant C-w, Curie-Weiss-like constant C' and the critical exponent gamma obtained from the analysis of dielectric constant data clearly suggest that the ferroelectric to paraelectric phase transformation undergoes a crossover from sharp to diffuse phase transformation for Sn concentrations in the range from 0.05 to 0.1. (C) 2001 Kluwer Academic Publishers.