Effects of mechanical activation on the formation of PbTiO3 from amorphous Pb–Ti–O precursor

Abstract

We investigate the effects of mechanical activation in triggering PbTiO3 (PT) formation from an amorphous Pb–Ti–O precursor synthesized by coprecipitation. In this work, the amorphous precursor and the samples derived from it by mechanical activation were investigated using Raman spectroscopy, x-ray diffraction, and high-resolution transmission electron microscopy. Our results show that the crystallization of tetragonal PT phase can be considered as a nucleation and growth process described by the Avrami model. In the initial stage of mechanical activation, the main effect is size reduction of the constituent starting materials. For a longer period of milling, perovskite PT crystallites are formed by mechanical activation alone. These crystallites act as seeds, reducing the activation energy from 249±6 kJ/mol for the precursor to 97±7 kJ/mol for the 30-h-milled sample and enhances the crystallization kinetics, during postcalcination. Consequently, the PT phase formation temperature is dramatically lowered. In addition, our results demonstrate that the particle size affects the structure of the PT phase, where the PT shows the pseudocubic to tetragonal transition with increasing particle size.