Relaxor behavior of pulsed laser deposited ferroelectric (Pb1-xLax) (Zr0.65 Ti0.35)O3 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 experimentally. Epitaxial stoichiometric PLZT films were formed on a pulsed laser deposited layer of La0.5Sr0.5CoO3 (LSCO) on MgO (100) single-crystal substrates. The dielectric permittivity and loss tangent of the resulting heterostructures were measured in the temperature range of 20-350 degrees C at 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 exhibited 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 ceramic PLZT and it also depended on the La content and microstructure of the film. The broadening depended on the temperature and frequency ranges: master curves of the normalized dielectric permittivity versus normalized temperature were obtained for PLZT films. The results are discussed in terms of the random field theory for relaxor ferroelectrics and the models for finite-size ferroelectrics. (C) 1998 American Institute of Physics. [S0021-8979(98)05224-4].