Synthesis and Structural Characterization of Sol-Gel Derived Barium Zirconium Titanate Thin Films
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Synthesis and structural characterization of Sol-Gel Derived Barium Zirconium Titanate Thin Films A. Dixit, A. Savvinov, S.B. Majumder, R.S. Katiyar R. Guo* and A.S. Bhalla* Department of Physics, University of Puerto Rico, San Juan, PR-00931-3343 * Material Research Laboratory, Pennsylvania State University, University Park, PA 16802 ABSTRACT Barium zirconium titanate (BZT) thin films are attractive candidates for dynamic random access memories and tunable microwave devices. In the present work a wide range of Zr doped BaTiO3 thin films have been prepared by sol-gel technique. X-ray diffraction and micro-Raman scattering studies confirmed the structural phases in the powder and film of BZT and various structural transitions of BaTiO3 as a function of different Zr content compared well with the published result on ceramics and single crystalline BZT. The deposited films had smooth, crackfree and homogeneous microstructure and Zr content has strong influence on the evolution of the microstructures of the films. Some selected compositions of these films were characterized in terms of their dielectric properties and phase transition behavior. BZT film with 20 at % Zr had a ferroelectric to paraelectric transition in the vicinity of room temperature. Efforts are underway to optimize the annealing condition and grow epitaxial BZT films, with various Zr contents, on a suitable single-crystalline substrate. INRTODUCTION Recently, the interest in high strain piezoelectric materials is increasing for various electrochemical transducers and related applications. Though, the large family of lead based perovskites and relaxor have shown a great potential, lead free compositions in these families will be of interest because of the obvious environmental concerns. In the paraelectric state BZT thin films are attractive candidates for making dynamic random access memories and tunable dielectric devices. While it is difficult to achieve high quality Pb based relaxor thin films, (BaZrTi)O3 thin film may have higher chance of success in fulfilling those goals. BaTiO3 is known to have a large electromechanical coupling factor. Substitution of Ti4+ (atomic weight 47.9, ionic radius 74.5 pm) with Zr4+ (atomic weight 91.2, atomic radius 86 pm) exhibits several interesting features in the dielectric behavior of BaTiO3 ceramics. When the Zr contents are less than 10 at % then BZT ceramics show normal ferroelectric behavior and the dielectric anomalies corresponding to the cubic to tetragonal (Tc), tetragonal to orthorhombic (T2) and orthorhombic to rhombohedral (T3) have clearly been observed. At about 27 at % Zr doping BZT ceramics exhibit typical diffuse paraelectric to ferroelectric phase transition behavior but films with higher Zr compositions exhibit typical relaxor behavior in which the Tc shifts to higher temperature with increase in frequency [1] The modified Ba(ZrTi)O3 have shown the systematic change in the dielectric, piezoelectric & phase transition characteristics in the bulk ceramic and single crystal forms [2]. In this paper
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