Raman study of overlap of phase transitions in Zr-doped barium titanate ceramics

Micro-Raman study in the temperature range of 70-575 K was performed to investigate the overlap of the basic phase transitions in barium titanate ceramics and single crystals of low Zr concentration. The possibilities of stress and grain size effects that are crucial for the optimization and reproducibility of the property coefficients were ruled out in these ceramics considering the Raman mode frequencies. The tetragonal to cubic transition temperature is found to decrease by increasing Zr-content. The orthorhombic to tetragonal transition temperature that increases with an initial increase in Zr-content merges with tetragonal-cubic transition for x>=0.15 compositions. The merging of phase transitions in these compositions is supported by the temperature dependent dielectric measurements.