Influence of processing parameters on dielectric properties of PZT thin films on steel substrates

Abstract
PZT thin films with a stoichiometry close to the morphotropic phase boundary were prepared on metallic susbtrates by a modified sol gel processing. Single layer film thicknesses of about 0.9 µm were obtained, by multiple coatings films up to 5 µm could be prepared. Hysteresis loops were obtained with a remanent polarization of about 35 µC/cm² and a coercivity of about 10 V/µm for an applied field strength of 50 V/µm. Dependent on the solvents used for the sol preparation the dielectric breakdown was about 50 V/µm for films with a high amount of triethanolamine (TEA) in the solution and more than 70 V/µm for films prepared with less TEA. By chemical analysis of the crystalline samples a significant lead loss was found compared to the lead content of the deposition solutions. By XRD measurements secondary phases were found for a molar lead excess of about 35 % in the deposition solutions. The influence of the lead content on the small and large signal dielectric properties was investigated. Best ferroelectric behavior was found for a molar lead excess of 30 % in the solutions, corresponding to a final film composition of Pb_1,10Zr_0,53Ti_0,47O₃.