Interactions between alumina and PLZT thick films

For some applications, piezoelectric (Pb,La)(Ti,Zr)O3 solid solution (PLZT) thick films are screen-printed and fired on platinum-metallized Al2O3 substrates. In this work, the compatibility and adhesion between PLZT thick films, the thick film platinum electrode, and the alumina substrate was investigated. Microanalysis of PLZT/Pt/Al2O3 structures after the firing process showed a secondary phase with β-Al2O3 structure at the interface between Pt and Al2O3, with a nominal composition of PbAl12O19, doped with La2O3 and TiO2 from PLZT and partly with oxides originating from impurities in alumina (CaO and MgO). As this compound could not be synthesized from pure oxides the results indicate that the other oxides are needed to promote the formation of a β-Al2O3 type compound. The formation of this compound results in significantly decreased adhesion between the PLZT/Pt layer and the alumina substrate.