We have studied the relaxor behavior of sol-gel derived Ba(Zr x Ti 1−x )O 3 (0.30≤ x≤0.70) thin films. The plausible mechanism of the relaxor behavior has been analyzed from the dielectric data and micro-Raman spectra. Substitution of Zr +4 for Ti +4 in BaTiO 3 lattice reduces its long-range polarization order yielding a diffused paraelectric to ferroelectric phase transition. The solid solution system is visualized as a mixture of Ti +4 rich polar region and Zr +4 rich regions and with the increase in Zr contents the volume fraction of the polar regions are progressively reduced. At about 25.0 at% Zr contents the polar regions exhibit typical relaxor behavior. The degree of relaxation increases with Zr content and maximizes at 40.0 at% Zr doped film. The frequency dependence of the polar regions follows Vogel-Fulcher relation with a characteristic cooperative freezing at freezing temperature (T f T T ). Below T f , a long range polarization ordering was ascertained from the polarization hysteresis measurement. C 2006 Springer Science + Business Media, Inc.
IntroductionRelaxors exhibit unusually higher dielectric constant and piezoelectric constants, which are very attractive for high energy density capacitors and actuators. Lead based perovskite ceramics has been extensively studied in last couple of decades. Studies on relaxors in thin film form are scanty and the available reports mostly are based on lead based perovskite thin films. These relaxor, irrespective in bulk ceramics or thin film forms have the following general characteristics: (i) all of them exhibit a diffuse phase transition (DPT) like behavior, where the temperature corresponding to the dielectric maxima (T m T T ) does not correspond any paraelectric-ferroelectric phase transition like normal ferroelectrics, (ii) T m T T shifts to higher temperature with the increase in measurement frequency, (iii) a frequency dispersive behavior is also observed in the dielectric loss tangent, however, the peak temperatures (T m T T ) for dielectric loss do not coincide with the corresponding T m T T (iv) relaxors follow the Curie-Weiss law far above T m T T , (iv) if the temperature is significantly lowered as compared
