Synthesis of lead zirconate titanate from an amorphous precursor by mechanical activation

Many of the chemistry-based processing routes for functional ceramics inevi tably involve calcining the chemical-derived precursors at an intermediate/ high temperature, in order to form the designed ceramic phase. This is very undesirable, although widely used, as the calcination can result in an ext ensive degree of crystal growth and particle coarsening at the calcination temperature and therefore ruins almost all the advantages offered by the ch emistry-based processing routes, such as an ultrafine particle size and hig h sintering-reactivity. Using a specifically designed PZT precursor prepare d by co-precipitation, it is demonstrated that the precursor-to-ceramic con version can alternatively be realized by mechanical activation. In this con nection, a single phase, nanocrystalline perovskite PZT powder has been suc cessfully derived from an amorphous hydroxide precursor by mechanical activ ation. The resulting PZT powder was well dispersed, and the particle size w as in the range of 30-50 nm, as observed using the scanning electron micros copy and transmission electron microscopy. This is in contrast to the poor particle characteristics, represented by very coarse and irregular particle and agglomerate sizes, for the powder derived from calcination at 750 degr ees C. The activation-triggered PZT powder was sintered to a density of 97. 6% theoretical density at 1150 degrees C for 1 h. Sintered PZT ceramic exhi bits a dielectric constant of 927 at room temperature and a peak dielectric constant of similar to 9100 at the Curie point of 380 degrees C when measu red at the frequency of 1 kHz. (C) 2000 Elsevier Science S.A. All rights re served.