Structural and electrical properties of electrophoretically deposited KNN and PZT thick films

KNN, (K_0.5Na_0.5)NbO₃ powder was synthesized from raw materials, and the PZT powder was prepared from commercial PZT powder (Alpha ceramics, Inc.). After a ball milling process, each KNN and PZT powder was uniformly deposited on Pt coated alumina plates up to 200 mum and 230 mum thick films, respectively. Several chemical additives such as PEI dispersant, PVB as polymer binder, glacial acetic acid and tetrumethyl ammonium hydroxide were varied to investigate their roles in the sintering process and the stability of chemical solution for electrophoretic deposition. The effect of additives on the sintering was not significant, but the stability of the solution and uniformity were strongly influenced by additives. Deposited films were sintered ranging from 850degC to 1100degC. The densest film was obtained at a sintering temperature of 1050degC. Excess addition of raw material K₂CO₃ could eliminate secondary phases in KNN thick films after sintering. Electrical properties of thick films were investigated by characterizing the ferroelectric hysteresis loops, dielectric properties, and piezoelectric properties.