An improved thick-film piezoelectric material by powder blending and enhanced processing parameters

This paper details improvements of the d₃₃ coefficient for thick-film lead zirconate titanate (PZT) layers. In particular, the effect of blending ball and attritor milled powders has been investigated. Mathematical modeling of the film structure has produced initial experimental values for powder combination percentages. A range of paste formulations between 8:1 and 2:1 ball to attritor milled PZT powders by weight have been mixed into a screen-printable paste. Each paste contains 10% by weight of lead borosilicate glass and an appropriate quantity of solvent to formulate a screen printable thixotropic paste. A d₃₃ of 63.5 pC/N was obtained with a combination of 4:1 ball milled to attritor milled powder by weight. The improved paste combines the high d₃₃ values of ball and the consistency of attritor milled powder. The measured d₃₃ coefficient was further improved to 131 pC/N by increasing the furnace firing profile to 1000degC, increasing the poling temperature to 200degC, and using gold cermet and polymer electrodes that avoid silver migration effects and repeated firing of the PZT film