POWDERS OF PB(ZRXTI1-X)O3 BY SOL-GEL COATING OF PBO

Powders of lead zirconate titanate (PZT) are prepared by coating a PbO powder with very fi ne particles containing titanium and zirconium derived from an alkoxide sol. The size of the particles in the coating increases from 10 nm to 100 nm with the increase in the pH during preparation from 3 to 10.5. The powders calcine at low temperature (similar or equal to 600 degrees C) to single-phase PZT without the formation of any intermediate phase. The tetragonal and rhombohedral phases are found to coexist between x = 0.535 and 0.545. Careful calcination of the powders is needed to ensure removal of residual organics; otherwise the residual carbon reduces PbO to metallic lead leading to high currents during poling. Loss of lead on sintering is significantly lower (1.4 wt %) as compared to samples from conventional powders (6.4 wt %). Successful poling of the sintered samples is achieved when the powders are prepared without using sol stabilizers and are calcined without pelletizing. Washing of the powders is not helpful, perhaps because it leads to change in stoichiometry due to loss of material. A dielectric constant of 950 and d(33) >190 PC N-1 are easily achieved.