Ferroelectric behaviour of PZT thin films with secondary TiO2 phase induced defects

The dielectric properties and ferroelectric phase transition in tetragonal lead zirconate titanate (PZT) thin films containing titanium oxide (TiO2) a s a secondary phase have been studied. TiO2 phase inclusion is observed in PZT films prepared by the electron beam evaporation of multicomponent oxide s as the result of the dissociation of the pyrochlore PbTi3O7 phase on high -temperature annealing. TiO2 phase inclusion results in the asymmetry of th e dielectric hysteresis along the polarization axis. Micro polar regions du e to defects caused by TiO2 are responsible for the latter. These regions b ecome randomized due to thermal energy and, as a result, the dielectric hys teresis becomes symmetrical. Investigation of the complex permittivity reve als that the relaxation time decreases with an increase of temperature and, as a result, non-Debye-like behaviour at low temperature gives way to Deby e-like behaviour suggesting that the material comprises a large number of r elaxing regions. Measurement of the dielectric constant revealed that the f erroelectric-paraelectric phase transition is diffused and shifts to the hi gh-temperature side with a measurement frequency characteristic of the rela xer-like behaviour. This transition follows the quadratic (T - T-o)(2) law instead of the Curie-Weiss law for normal PZT films. A value of 48 degrees C was obtained for the diffuseness of the phase transition.