PZT thick films for sensor and actuator applications

PZT thick films with thicknesses between 5 and 150 μm are of great interest for microsystems applications where direct coating onto microelectronic substrates and high electromechanical performance are required. Dense PZT thick films have been obtained by combining a PZT-PMN powder with a low melting point glass and the eutectic forming oxides Bi2O3 and ZnO. Densification is due to transient liquid phase formation with additional incorporation of cations into the growing PZT grains during sintering. PZT thick films prepared by this method show excellent dielectric, ferroelectric and piezoelectric properties. They have been applied on various substrates, like Al2O3, ZrO2, Low Temperature Cofired Ceramics (LTCC) and silicon wafers which are basis materials for microsystems technology. The influence of the substrate material on the PZT thick film properties and the role of buffer layers will be discussed.