Phase Transitions in BaTiO₃ from IR Autocorrelation Spectrum

Temperature dependence of infrared spectrum from BaTiO ₃ micro-crystals has been analysed. The measurements have been made within temperature range from 140 to 330 K in the IR region between 380 and 4000 cm⁻¹ . The low temperature spectrum shows two clear bands at about 498 and 550 cm⁻¹ that are in agreement with expectations for trigonal symmetry. The spectra at higher temperatures have the profiles that are difficult to be interpreted using a conventional peak fitting procedure. To explain the obtained results an autocorrelation method has been used for the frequency region between 480 and 700 cm⁻¹ (where IR active vibrations occur). A special attention has been paid to the effects following the phase transitions. It has been possible to formulate some additional arguments concerning a complex character of the phase transitions in barium titanate with indication of an increasing role of order-disorder mechanism.

Keywords:

• Barium titanate phase transitions
• IR spectroscopy
• order-disorder
• autocorrelation analysis

Acknowledgments

This work has been supported by POLONIUM, no. 4937.II/2003/2004.