Effects of pH and H₂O₂ upon coprecipitated PbTiO₃ powders - Part I Properties of as-precipitated powders

The properties of precipitated materials are highly dependent upon the complex ionic equilibria of the species in the solutions used for precipitation. Concentration, temperature, and pH dictate the complex species present within aqueous systems, and therefore affect the final precipitate properties. This paper discusses the effect of pH on the properties of PbTiO₃ precursor powders prepared by adding stoichiometric mixtures of TiCI₄ and Pb(NO₃)₂, in aqueous solution, to NH₄OH solutions. Several powders were prepared between pH 8.00 and 10.50. The pH does not affect the amorphous structure, but does have a pronounced effect upon the specific surface area and growth mechanisms of the precipitates. Since previous studies indicated that hydrogen peroxide (H₂O₂) affects the hydroxylation of the precipitated powders, the effect of (H₂O₂) concentration on the precipitate properties was also studied. Several precipitates were prepared from solutions containing (H₂O₂): PbTiO₃ ratios between 0:1 and 6:1. When (H₂O₂) was not added to the solutions used for precipitation, atmospheric CO₂ dissolved in solution caused precipitation of carbonate species. Thus, addition of the (H₂O₂) to the solutions inhibited precipitation of the carbonates.