Subpeak structure of the lowest-frequency E-symmetry transverse optical phonon in Ba-doped PbTiO3 single crystals

Abstract

Polarized Raman scattering study of Ba-doped PbTiO3 single crystals indicated that, for a limited temperature range between 650 and 750 K, the line shape of the E(1TO) "soft" mode could not be described by a single damped harmonic oscillator but was adequately fitted by two independent oscillators. The line-shape fitting of the E(1TO) spectrum further indicated a gradual intensity inversion between the two subpeaks with increasing temperature. For temperatures below the crossover point, the subpeak with a higher mode frequency dominated the line shape. Contrary to this, the line shape was predominantly described by the subpeak with a lower frequency for temperatures above the crossover point: The subpeak structure becomes progressively evident with increased content of barium (Ba) dopant. We examined possible origins of the observed subpeak structure with the crossover in the integrated intensity and attributed this anomalous behavior to localized defects caused by the Ba impurity. (C) 2003 American Institute of Physics.