Influence of hydrolysis conditions of the acetate sol–gel process on the stoichiometry of PZT powders

Abstract [Pb(Zr,Ti)(OAc) x (OR) y ] acetate-alkoxide precursor was prepared by chelating from organic Pb, Zr and Ti alkoxides by their dissolution in various amounts of acetic acid (AcOH). Sols were formed by hydrolysis of acetate-alkoxides with ethylene glycol and transformed by polycondensation to a gel at 80 °C. The final stoichiometry of prepared PZT gels was determined by chemical analysis after their filtration and calcination at 500 °C. As results from the DTA/TGA, IR and XRD analysis, the optimum mole ratio of (Pb+Zr+Ti) to AcOH for preparation of viscous polycondensed stoichiometric gel is 1:7 and a pure perovskite phase is formed at 500 °C. The stoichiometric ratio in PZT calcinate was degraded after increasing the added amount of AcOH. At a low AcOH concentration, two-phase (pyrochlore and perovskite) regions are formed during gellation. At 700 °C, the decomposition of a pyrochlore phase and the formation of a perovskite phase takes place despite significant cation nonstoichiometry in PZT powders.