Low temperature synthesis of lead titanate by a hydrothermal method
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Low temperature synthesis of lead titanate by a hydrothermal method Jooho Moon and Tuo Li Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611
Clive A. Randall Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802
James H. Adair Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (Received 9 February 1996; accepted 1 October 1996)
Alkoxide-based hydrothermal powder synthesis of lead titanate was investigated. The objective of this work was to lower the synthesis temperature. By modifying titanium isopropoxide with acetylacetone during solution mixing, the phase-pure lead titanate with perovskite structure was synthesized at temperatures as low as 150 ±C. It was determined that the pH of the hydrothermal reaction medium and the initial PbyTi ratio are critical factors in forming stoichiometric PbTiO3 . When the pH of the initial feedstock is above 14 and the PbyTi ratio is greater than 1.5, a phase-pure PbTiO3 can be obtained. The modification of titanium alkoxide gave rise to the formation of a stable complex against hydrolysis and eventually reduced the synthesis temperature significantly. A possible formation mechanism for PbTiO3 is the dissolution-recrystallization from an amorphous precursor to a well-crystalline product as originally proposed by Rossetti et al. Hall–Williamson analysis was also performed on the hydrothermally derived PbTiO3 to interpret the systematic peak broadening and asymmetry for h001j reflections, unlike the commercial PbTiO3 . It was observed that the strain in the c-axis direction is much higher than that in the a-axis direction while the domain sizes for both directions are similar. This strain anisotropy exerted in the particles may indicate a unique domain structure in the hydrothermally synthesized particles in which either only 180± domains exist or possibly only a single domain.
I. INTRODUCTION
Recently, significant research has been conducted on the chemical synthesis of materials from solution as a nonconventional powder preparation technique in contrast to traditional solid state reaction methods. The principal benefits of solution synthesis techniques include the high degree of chemical homogeneity achieved on the molecular scale in the solution state, which subsequently results in ceramic powders with high-purity, controlled size, and morphology.1,2 These characteristics enhance the sinterability to produce dense, fine-grained microstructure that tends to exhibit improved physical properties.3–5 Lead titanate (PbTiO3 ) is a ferroelectric material with a variety of applications which involve multilayer capacitors, resonators, and ultrasonic transducers.6 PbTiO3 has been prepared via liquid phase techniques such as sol-gel,7 coprecipitation,8 decomposition,9 hydrothermal,10,11 and molten salt methods,12 as well as conventional solid state reaction.13 In particular, extens
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