Falko Schlenkrich

Self-polarization and texture of wet chemically derived lead zirconate titanate thin films

Abstract A multilayer structure of Si/SiO2/Ti/Pt/TiO2 was used as a bottom electrode for pyroelectric Pb(Zr0.25Ti0.75)O3 (PZT) thin films. A wet chemical approach was used for PZT deposition. The interrelations between the bottom electrode and the crystallographic orientation of the PZT thin films as well as correlations between microstructure and electrical properties were studied in detail. Annealing of Ti/Pt electrodes prior to PZT deposition caused Ti diffusion and oxidation, which influenced texture and film quality. The combination of a sputtered TiO2 seed layer with an intermediate heating step at around 400°C yielded dense and columnar PZT(111). The films showed a pyroelectric coefficient and a built-in polarity after preparation.

Investigation of domain switching of PZT and KNN - based ceramics

As known, ferroelectric ceramics generate strain and stress against an external clamping at high electric fields, which is used in actuator applications. To understand this response quantitatively bulk samples of commercial PZT and in-house produced KNN ceramics were investigated in model experiments. On bulk samples, the typical non-linear polarization hysteresis is found in a wide temperature range TN…TC. Below the characteristic temperature TN polarization reversal is suppressed, which is explained by domain wall pinning. The applied energy by the external electric field is too low to overcome the critical pinning energy barrier U/kT. Experimental results of measured threshold electric field and energy for domain switching are given for Sonox P 53 and KNN based ceramics.