Lead zirconate titanate particle dispersion in thick-film ink formulations

Diverse device applications for lead zirconate titanate (PZT) ceramics in t hick-film form are currently in active development. In the present study, t he particle dispersion properties of thick-film ink formulations containing PZT powder have been determined using rheological measurements. Although a ll of the eight commercially available dispersants tested are more effectiv e than the terpineol solvent alone in decreasing attractive interparticle f orces in suspensions, the best dispersant identified for hard and soft PZT powders is a phosphate ester oligomer. This dispersant is extremely efficie nt, and its use in thick-film ink formulations results in viscosity decreas es of 50% at low shear rates (10 s(-1)) and 30% at high shear rates (100 s( -1)) compared with current ink formulations containing no dispersant. The e ffects upon rheology of the order of addition of components in the processi ng of inks have been studied, with the most effective processing route usin g a fugitive solvent that probably facilitates uniform coverage of the part icle surfaces by the dispersant molecules. Modeling of the rheological prof iles of inks indicates that the use of a dispersant decreases the depth of the primary minimum in the interparticle potential by a factor of 3. Demons trated advantages of the use of a dispersant in PZT thick-film inks include improved microstructural homogeneity in the green body and the ability to formulate printable inks with higher solids loadings. No adverse effects of the dispersant upon the dielectric and piezoelectric properties of bulk PZ T samples are found following burnout and sintering.