Y. Deng et al., Structural and phonon characteristics of PbxLa1-xTiO3 nanocrystals prepared by hydrothermal technique, MAT SCI E B, 84(3), 2001, pp. 248-251
Pb1-xLaxTiO3 (PLT) nanocrystals of various La concentrations were prepared
by hydrothermal technique. Raman spectroscopy, X-ray diffraction (XRD) and
thermal gravity analysis (TCA) were used to investigate the lattice structu
res, phonon properties and volatile behaviors. With increasing La concentra
tion, most of Raman modes shift downward. A soft mode E(ITO) at 82 cm(-1) s
hifts and disappears at 60 cm(-1) when the La concentration reaches 14 mol.
%. This weaker softening property of the soft mode is attributed to the dec
rease of the tetragonality by La doping. Grain sizes of the PLT nanocrystal
s from 12 to 28 nm were obtained at various annealing temperatures by X-ray
measurement, via the Sherrer formula. The saturation for grain growing bec
omes more appreciable with increased La doping, owing to mon 'pinning cente
rs' inside. When the La concentration is over 12 mol.%, after 1000 degreesC
heat treatment a PbTi3O7 impurity phase appears in PLT nanocrystals due to
PbO volatilization. The volatile temperature for PbO from PbTiO3 lattice d
ecreases with increasing La concentration. (C) 2001 Elsevier Science B.V. A
ll rights reserved.