PbTiO3 fine particles were prepared by a hydrothermal method. TEMobservation showed that as-prepared particles were PbTiO3single-crystals with a size of 8.57 nm. XRD measurement also revealedthat its shape was plate-like. Moreover, an investigation of chemicalcomposition resulted in no impurity such as lattice hydroxyl groupand potassium. The particles were calcined at various temperature,and the average sizes increased from 8.57 to 55.1 nm. At the sametime, the shape were also changed from plate to sphere gradually. Allparticle's symmetries using XRD and Raman scattering were assigned toP4mm. However, a tetragonality of the as-prepared PbTiO3 was l.l13,and was much greater than l.065 reported in PbTiO3 single crystal.The tetragonality decreased with increasing particle size below 20nni, while above 20 nm the tetragonality increased with increasingparticle size. We discussed about the origin of these abnormal sizedependence.
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