Direct observation of the soft mode in the paraelectric phase ofPbTiO3by confocal micro-Raman scattering

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

“…Raman Spectroscopy studies have shown that this system undergoes a typical displacement ferroelectric phase transition observed by the soft sub damping of the low frequency fanon [1,5,13]. In a study by Burns et al [6] and others [1,2,9,12], show that the optical transverse mode E1 of lower frequency can observe the transition of ferroelectric-paraelectric phase in the PLT. On the other hand, the optical cross A1 as first studied by Foster et al [12] and found in ±148 cm 1 show that it is also indicative of the structural phase transition; however, the author discusses the anomalous behavior of A1 but gives no definitive explanation of the vibrational mode shape.…”

“…The PbTiO 3 (PT) is one of most studied ferroelectric materials in basic research and industrial applications [3][4][5][6][7][8][9][10][11]. In the literature there are many arguments about the nature of the phase transition of PbTiO 3 such as a displacement or order disorder transition.…”

Influence of KF substitution on the ferroelectric phase transition of lead titanate single crystals studied by Brillouin light scattering

“…1,2 Recent confocal Raman investigation revealed the soft mode even in the paraelectric phase. 3 On the other hand, X-ray absorption finestructure (XAFS) measurements revealed that the Pb and Ti ions are displaced from their ideal positions in the perovskite structure even above T c . 4 These local distortions (local instabilities) indicate that order-disorder nature exists even in this, treated often as classical, displacive ferroelectric material.…”

“…Perovskite lead titanate (PbTiO 3 ) is an archetypal ferroelectric material that undergoes a ferroelectric phase transition from cubic (m3m) to tetragonal (4 mm) symmetry at $ 490 C (T c ). The phase transition of PbTiO 3 is considered as a typical displacive-type ferroelectric, because underdamped soft modes in the tetragonal ferroelectric phase are observed by neutron and Raman scattering studies.…”

“…[8][9][10] Elastic constants were determined at room temperature or over a limited temperature range. 8,9 The linewidth of the longitudinal acoustic (LA) mode was determined in the paraelectric phase and compared to that of BaTiO 3 . 11,12 The LA mode of BaTiO 3 in the cubic phase exhibits substantial softening on approaching T c .…”