Effects of particles size on the vibrational modes of ultrafine lead titanate particles

Raman Spectroscopy

“…In 1996, Lehnert and co-workers reported that Raman intensity increased with decreasing particle size (418). Corresponding results are obtained with PbTiO 3 ultrafine powders (419). Both theoretical and experimental examinations of Si nanocrystals relating particle size and Raman peak intensity have appeared (420,421).…”

Examination of Size-Induced Ferroelectric Phase Transitions in Template Synthesized PbTiO3 Nanotubes and Nanofibers

“…The nanotubes had an E(1TO) frequency of 85 cm -1 . Similar room-temperature Raman spectra have been reported by Fu et al for nanocrystalline material made by sol−gel having a 17-nm average crystallite size and by Zhou et al for 18-nm crystallites . A broad and undefinable spectrum was also reported by Zhou et al for a sample with 15-nm crystallite size .…”

“…In reviewing the experimental literature on size effects upon the PbTiO 3 ferroelectric phase transition, it is difficult to determine an exact critical size. PbTiO 3 nanoparticles, with crystallites on the order of 8−200 nm, have been prepared by the sol−gel, chelate, nitrate, citrate, coprecipitation, Pechini, and injection−hydrolysis procedures, and various physical characterization and theoretical techniques have been employed to acquire the critical size. − ,− ,,,− Therefore, we compared our results of the nanotubes and fibers to those of control samples made with the same solution chemistry in the absence of any templates.…”

“…Thus, we have begun our investigation on this system by producing nanotubes and fibers of PbTiO 3 . In contrast to BaTiO 3 , few studies have appeared that address size effects in PbTiO 3 systems. − Here we report on the examination of the ferroelectric phase transition of PbTiO 3 nanotubes and nanofibers as the particle size and potentially the aspect ratio are controlled. To our knowledge, this is the first report on size-induced ferroelectric phase transition temperature ( T c ) deviations for 1-D constrained perovskites.…”

Raman spectra and structural phase transition in nanocrystalline lead lanthanum titanate

“…The intensity of the A 1 (1TO) phonon mode weakens when the grain size is smaller, and the peak wave number of about 150 cm Ϫ1 at a grain size of 57 nm is in good agreement with our previous result of tetragonal PT. 20 However, the main differences in the A 1 (1TO) phonon mode between PT and PLT are the intensity changes with grain sizes; its intensity in PT is larger than in PLT with similar grain size. This is because the A 1 (1TO) phonon mode at kХ0 in the tetragonal perovskite system corresponds to vibrations of the lead ion with respect to the slightly distorted TiO 6 octahedra in which the displacement polarization is determined by the tetragonal distortion (c/a).…”