Ferroelectric behaviour of PZT thin films with secondary TiO₂phase induced defects

Abstract

The dielectric properties and ferroelectric phase transition in tetragonal lead zirconate titanate (PZT) thin films containing titanium oxide (TiO2) as a secondary phase have been studied. TiO2 phase inclusion is observed in PZT films prepared by the electron beam evaporation of multicomponent oxides as the result of the dissociation of the pyrochlore PbTi3O7 phase on high-temperature annealing. TiO2 phase inclusion results in the asymmetry of the dielectric hysteresis along the polarization axis. Micro polar regions due to defects caused by TiO2 are responsible for the latter. These regions become randomized due to thermal energy and, as a result, the dielectric hysteresis becomes symmetrical. Investigation of the complex permittivity reveals that the relaxation time decreases with an increase of temperature and, as a result, non-Debye-like behaviour at low temperature gives way to Debye-like behaviour suggesting that the material comprises a large number of relaxing regions. Measurement of the dielectric constant revealed that the ferroelectric-paraelectric phase transition is diffused and shifts to the high-temperature side with a measurement frequency characteristic of the relaxor-like behaviour. This transition follows the quadratic (T-T0)2 law instead of the Curie-Weiss law for normal PZT films. A value of 48 °C was obtained for the diffuseness of the phase transition.

Composition and Crystal Phase Control of Chemical-Vapor-Deposited Pb(Zrx,Ti1-x)O3 Films on Various Oxide Electrodes with Reactants Pb(C2H5)4, Zr(O-t-C4H9)4, Ti(O-i-C3H7)4 and O2

“…5(b) was so leaky. 19) A similar trend was found in the P-E hysteresis loop measurements for the Pb excessive PZT layers grown on IrO 2 (not shown here). Emphasis should be placed on the significant improvement in ferroelectric properties for the PZT layers due to improvement in PZT film composition and crystalline properties using the TEL concentration adjustment strategy.…”