Effects of temperature and concentration of La in the form of A1 transverse optical phonon in the PbTiO3 system

Abstract

The structural phase transition from ferroelectric to paraelectric was studied by Raman scattering in the ceramic lead titanate (PbTiO 3 ) doped with lanthanum (La). A1 vibrational mode contains some sub-peaks that have been associated in literature with PbTiO 3 concentration (Ca, Ba), and effects of high temperatures as it approaches the Curie temperature (Tc). Raman new study shows that the anomalous behavior of the A1 mode is not only caused by the effects of concentration or temperature near Tc, but by anharmonicity and defects in the network in the PbTiO 3 thermodynamically are inevitable. This effect was studied by a wide temperature range from 10 K to Tc in each sample (La = 0,5,10, 15, 20%), showing that the effect depends not only on the high temperatures in the pure PT. Keywords: PbTiO 3 , ferroelectric, paraelectric, anharmonicity. (La = 0,5,10, 15, 20%) Resumo A transição de fase estrutural de ferroelétrico para paraelétrico foi estudada por espalhamento Raman em cerâmicas de titanato de chumbo (PbTiO 3 ) dopadas com lantânio (La