Synthesis and characterization of PbTiO 3 powders and heteroepitaxial thin films by hydrothermal synthesis
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Synthesis and characterization of PbTiO3 powders and heteroepitaxial thin films by hydrothermal synthesis A.T. Chien,a) J. Sachleben,b) J.H. Kim,c) J.S. Speck, and F.F. Lange Materials Department and Materials Research Laboratory, University of California, Santa Barbara, California 93106 (Received 28 July 1998; accepted 27 April 1999)
PbTiO3 powders and heteroepitaxial thin films were produced by the hydrothermal method at 110–200 °C using different bases (Na–, K–, Rb–, Cs–, TMA–, and TBA–OH). Microstructural characterization showed that the tetragonal perovskite films were epitaxial on the SrTiO3 substrates, with a c-axis out-of-plane orientation. Sequential growth experiments showed that the growth initiates by the formation of 100 nm {100} faceted PbTiO3 islands followed by coalescence. Small cation bases (Na–, K–, Rb–OH) produced 1.5-m {100} faceted blocky powders, whereas larger cation bases (Cs–, TMA–, and TBA–OH) formed fewer 500-nm interpenetrating platelets. Nuclear magnetic resonance results showed cation incorporation in the perovskite structure with local disorder on the Pb sites increasing cation size.
I. INTRODUCTION
Hydrothermal synthesis is a promising method for the manufacture of advanced ceramic powders and thin films. Investigations in this field were originally conducted by geologists studying the crystallization of rocks and minerals in the earth’s crust at high temperatures and pressures.1 Researchers are currently applying this method toward the synthesis of commercially significant ceramics such as quartz, zeolites, and BaTiO3.2–4 A new method was recently discovered for growing epitaxial single-crystal thin films that we call hydrothermal epitaxy. Hydrothermal epitaxy is a low-temperature solution route for creating heteroepitaxial thin films through the use of solution chemistry and structurally similar substrates. Film growth occurs at substantially lower temperatures than vapor methods, which diminishes the problems of high processing temperatures and the need for ultrahigh vacuum. An assortment of epitaxial perovskite thin films [e.g., Pb(Zr x,Ti1−x)O3 (PZT), (Nax ,K1−x)NbO3, and BaTiO3] have been produced by this synthesis route at temperatures from 90–200 °C.5–9
a)
Present address: Chemistry and Materials Science, Lawrence Livermore National Laboratory, L-370, Livermore, California 94551. b) Present address: Research Scientist, Solid-State NMR Facility, Campus Chemical Instrument Center, The Ohio State University, Johnston Laboratory 119, 176 W. 18th Ave., Columbus, Ohio 43210. c) Present address: Department of Ceramic Engineering, Chonnam National University, 300 Yongbong-Dong, Puk-Gu, Kwangju 500-757, Korea. J. Mater. Res., Vol. 14, No. 8, Aug 1999
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This provides a simple processing method for the formation of epitaxial perovskite thin films, which can also be applied to other ceramics of technologic interest. PbTiO3 and PZT powders and thin films have been made by the hydroth
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