Dielectric and electromechanical properties of sol-gel prepared PZT thin films on metallic substrates

This article reports about the dielectric and electromechanical properties of sol-gel derived ferroelectric PZT films on metallic substrates. PZT(53/47) films deposited directly on metallic substrates (Hastelloy C-276) show a strong thickness dependence of their dielectric and electromechanical properties as well. This dependence can be described by a model assuming an interface layer between substrate and PZT film. By applying an additional electrode between substrate and PZT film the formation of the interface layer can be minimized and a significant reduction of the thickness dependence as well as a general improvement of the film properties was observed. By varying the Zr/Ti-ratio it was found that the extrema of the dielectric and piezoelectric coefficients are shifted towards Ti-rich stoichiometries compared to bulk ceramics. For PZT thin films with optimized preparation conditions nearly rectangular hysteresis loops with a coercive field strength of 5 V/μm, a piezoelectric coefficient d33 of 96 pm/V and strains up to 0.4% were obtained. Antiferroelectric PZT (98/2) films could be deposited in a good quality on an oxidic electrode, too. The observed field-induced antiferroelectric–ferroelectric phase transition is accompanied by high strains. Furthermore, bending resonance modes of samples with different geometries and the tip displacement of a simple cantilever under a dc-field were investigated. By controlled bending of the substrate charges up to 0.3 μC/cm2 could be obtained. On the other hand, tip displacements of up to 30 μm could be realized by applying a voltage of 17 V/μm, respectively.