Studies on the relaxor behavior of sol-gel derived Ba(Zr x Ti1− x )O3 (0.30≤x≤0.70) thin films

Abstract

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

Raman spectral studies of Zr4+‐rich BaZrxTi1−xO3(0.5⩽x⩽1.00) phase diagram

“…These observations were in agreement with previous reports, where a similar behavior had been observed for BaZr 0.4 Ti 0.6 O 3 ceramics and thin films. [12,15,27] Similar temperature dependence has also been observed for other compositions as well. The dip at ∼120 cm −1 persisted at temperatures higher than the dielectric constant maximum (at ∼145 K), which suggested that the rhombohedral structure was retained in the whole temperature range studied.…”

“…The intensity variation in the present case did not show any plateau on cooling below freezing temperature as has been demonstrated for BaZr 0.4 Ti 0.6 O 3 . [12,27] This may be due to the fact that the freezing temperature for BaZr 0.5 Ti 0.5 O 3 is (∼26 K) well below the lowest temperature accessible in the present Raman measurements. [8] As both Zr and Ti have the same valency but differ slightly in their ionic radii, random distribution of Zr ions is not expected to give rise to strong random local electric fields that break longrange polar correlations.…”

Investigation of local structure of lead‐free relaxor Ba(Ti0.70Sn0.30)O3 by Raman spectroscopy

“…Micro-Raman spectroscopy is a valuable technique to investigate structure property relationship such as coherence length, phonon life time, vibrational state of imperfect material, dynamic behavior of optical modes, crystal symmetry, etc. [15] In this report, temperature-dependent Raman spectroscopic studies were done on lead-free Ba(Ti 0.70 ,Sn 0.30 )O 3 relaxors in order to understand the change in their local structure and symmetry. The sequences of transitions were observed as a function of temperature, i.e.…”

Fano resonance and dipolar relaxation in lead-free relaxors

“…In this study, all the aforementioned questions are addressed by investigating, analysing and comparing with experiments the complex dielectric response of disordered BZT crystal numerically obtained in the THz regime, via a combination of a first-principles-based effective Hamiltonian and a molecular dynamics (MD) technique. BZT is chosen because it is a lead-free relaxor that has already attracted a lot of attention 19,27,38,[44][45][46][47][48] . In relaxors, most experimental works were performed in the kilohertz regime, which is (unfortunately) not accessible by our MD techniques.…”