Relaxor behavior of pulsed laser deposited ferroelectric (Pb1-xLax) (Zr-0.65 Ti-0.35)O-3 films

The dielectric behavior of pulsed laser deposited ferroelectric (Pb1-xLax)( Zr0.65Ti0.35)O-3 films (PLZT x/65/35, x = 0-9.75 at. %) has been studied ex perimentally. Epitaxial stoichiometric PLZT films were formed on a pulsed l aser deposited layer of La0.5Sr0.5CoO3 (LSCO) on MgO (100) single-crystal s ubstrates. The dielectric permittivity and loss tangent of the resulting he terostructures were measured in the temperature range of 20-350 degrees C a t a frequency of 100 Hz-1 MHz. A peak around 130-350 degrees C was observed in the dielectric permittivity versus temperature curves. The peak exhibit ed a relaxor type behavior. Its position was a nonmonotonic function of the La content and depended on the microstructure of the film. The broadening of the peak of the dielectric permittivity was larger than that in the cera mic PLZT and it also depended on the La content and microstructure of the f ilm. The broadening depended on the temperature and frequency ranges: maste r curves of the normalized dielectric permittivity versus normalized temper ature were obtained for PLZT films. The results are discussed in terms of t he random field theory for relaxor ferroelectrics and the models for finite -size ferroelectrics. (C) 1998 American Institute of Physics. [S0021-8979(9 8)05224-4].