Interactions between alumina and PLZT thick films

For some applications, piezoelectric (Pb,La)(Ti,Zr)O-3 solid solution (PLZT ) thick films are screen-printed and fired on platinum-metallized Al2O3 sub strates. In this work, the compatibility and adhesion between PLZT thick fi lms, the thick film platinum electrode, and the alumina substrate was inves tigated. Microanalysis of PLZT/Pt/Al2O3 structures after the firing process showed a secondary phase with beta-Al2O3 structure at the interface betwee n Pt and Al2O3 with a nominal composition of PbAl12O19, doped with La2O3 an d TiO2 from PLZT and partly with oxides originating from impurities in alum ina (CaO and MgO). As this compound could not be synthesized from pure oxid es the results indicate that the other oxides are needed to promote the for mation of a beta-Al2O3 type compound. The formation of this compound result s in significantly decreased adhesion between the PLZT/Pt layer and the alu mina substrate. (C) 2000 Elsevier Science Ltd.