Crystallization Kinetics Of Metallo-Organics Derived Pzt Thin Film
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CRYSTALLIZATION KINETICS OF METALLO-ORGANICS DERIVED PZT THIN FILM K.C. Chen* and J. D. Mackenzie University of California, Los Angeles, Dept. of Materials Science and Engineering, Los Angeles, CA 90024 ABSTRACT PZT films on fused silica substrates were prepared by a multiple dipping-firing process from a stable solution of titanium isopropoxide, zirconium n-propoxide and lead 2ethylhexanoate. The crystallization kinetics of the amorphous PZT films was studied by quantitative X-ray analysis. The crystallization of the amorphous film to perovskite phase involved a transitional pyrochlore structure phase. The entire crystallization was described by a consecutive phase transformation process in which nucleation dominated. INTRODUCTION Crystallization of amorphous phases has been an interesting subject of both scientific and practical importance. During the past decade, there have been notable advances in understanding the nucleation and growth of crystals from glass-forming systems. Knowledge of crystallization has led to the ability to control the microstructure and the properties of glass-ceramics. Recently, the crystallization of amorphous systems which do not contain any glass formers have been studied. These systems include metallic glasses, splat-quenched materials, sol-gel and metallo-organics derived amorphous phases [1-7]. In the sol-gel and metallo-organic processing, low temperature processed materials were obtained and then converted to ceramics by calcination at high temperatures. During crystallization of sol-gel derived ceramics, metastable or transitional phases are often observed prior to the formation of the final stable phases [2,4]. Therefore, the crystallization process is usually not a single step transformation process. In this paper, the crystallization kinetics of lead zirconate titanate film which involved a transitional phase will be described. EXPERIMENTAL PROCEDURE Zirconium n-propoxide liquid+ was first introduced into an oven-dried 250 ml flask. A pre-determined amount of titanium isopropoxide* was added so that the final Zr/Ti ratio was 52/48. The solution was stirred for 2 to 4 hours before the required amount of lead 2ethylhexanoate* was added. The resulting solution, having a final composition of Pb(Zr0.52 Ti0 .48)O 3, was then stirred for 18 hours. The homogeneous solution was stored in a glass flask for later film preparation. After pyrolysis, the solution contained 28 weight percent of oxide. Isopropanol was used to dilute the solution into individual solutions with oxide contents of 7, 14, 17.5 weight percent. Fused silica substrates (1"xl" and 2"x2") were dipped into the solution and withdrawn at a constant speed of .75 crrmin. The dipped films were dried at 100'C for 20 minutes and then fired at 400oC for 20 minutes after each dip. This dipping-firing cycle was repeated until film thickness was, 2 pim. All substrates were processed under the same conditions to ensure the same thickness. X-ray diffraction was performed with a Norelco X-ray diffractometer. The intensities of the
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