Temperature-dependent, micro-Raman spectroscopic study of barium titanate nanoparticles.

A comparative, temperature-dependent (80-500 K at 5 K intervals), micro-Raman spectroscopic study of 300 and 50 nm diameter ceramic BaTiO₃ nanoparticles was carried out with the purpose of elucidating the nanoparticle size effect on the temperature dependence of the polar and non-polar phonons. A method for calibrating Raman intensities, along with an iterative spectral fitting algorithm, is proposed for concurrent Raman band position and intensity analysis, increasing the analytical abilities of single temperature point Raman spectroscopy. The 300 nm particles exhibit all three phase transitions, whereas the 50 nm particles do not show evidence of these phase transitions in the same temperature range. The Curie temperature appears to be a phonon converging point, irrespective of the phonon symmetry. An attempt was made to qualitatively relate the temperature-dependent Raman spectra to complimentary non-spectroscopic methods, such as heat capacity and X-ray diffraction studies. The study proves that the temperature-dependent behavior of the polar phonon, 265 cm⁻¹, can be utilized as a sensitive phase transition probe. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]