Raman spectra studies on (Ba,Sr)TiO3 ceramics under dc electric fields

Abstract

BaxSr1-xTiO3 (0.40≤x≤0.70) ceramics have been prepared by the conventional solid-state reaction method. The changes of vibration modes in the pure BaxSr1-xTiO3 system have been investigated for an in-situ electric field by Raman spectra, and the transition from the cubic phase to tetragonal phases were obviously observed near the Curie temperature (Tc). Detailed results indicate that the A1(TO3) and E(TO4) modes correspond to the vibrations of O-Ti-O bond along a-axis in the ab plane, which are strongly related to the lattice structure of ABO3. With increasing electric field, the intensity of A1(TO3)/E(TO4) ratio is increased, suggesting that more and more paraelectric states are transformed into ferroelectric states, thus leading to the deformation of lattice, which results in the decrease of dielectric constant and the increase of tunability. The electric-induced-structure phase transitions responsible for the nonlinear dielectric properties are also discussed.