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Wu, Zhibin; Tsukada, Tetsuji; Yoshimura, Masahiro

doi:10.1023/a:1004703420342

Cited by 12 publications

(6 citation statements)

References 32 publications

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“…However, no perovskite KTaO 3 phase could be obtained under these conditions. 39,40 Lange et al reported synthesis of epitaxial KTaO 3 films by low-temperature hydrothermal epitaxy at 175 °C. 41 The objective of this work was to synthesize orthorhombic KNbO 3 films with a single crystallographic orientation and hopefully also single-domain, on such single-crystal substrates as SrTiO 3 (100) and LiTaO 3 (001) by hydrothermal epitaxy at about 200 °C, i.e., below the phase-transition temperature of 225 °C.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis of Potassium Niobiate (KNbO₃) Thin Films by Low-Temperature Hydrothermal Epitaxy

Suchanek

2004

Chem. Mater.

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Orthorhombic KNbO 3 thin films were deposited on SrTiO 3 (100) and LiTaO 3 (001) substrates by low-temperature hydrothermal epitaxy at 180-210°C using aqueous solutions containing Nb 2 O 5 and KOH. The films were thoroughly characterized by X-ray diffraction, Rutherford backscattering, and scanning electron microscopy. The KNbO 3 films were uniformly distributed on the entire substrate area, exhibited high stoichiometry, and did not show evidence of interdiffusion or chemical reaction at the film/substrate interface. Their microstructures were determined by the substrate used, the synthesis temperature, and the concentration of the reactants. The KNbO 3 films on SrTiO 3 (100) substrates with thickness of 45 nm to 1.28 µm were smooth and transparent, with microstructures strongly suggesting single crystal growth mechanism. They were pure orthorhombic phase with (011) orientation and probably single-domain. Conversely, the KNbO 3 films with higher thickness (>3.5 µm) exhibited very rough microstructure with textured columnar grains. Such films were also orthorombic but with mixed (100)/(011) orientation. This work demonstrated for the first time deposition of heteroepitaxial KNbO 3 films on single-crystal substrates using low-temperature hydrothermal epitaxy in a well-defined range of synthesis conditions. The low synthesis temperatures, which are below the 225°C phase transition temperature of KNbO 3 , resulted in formation of films that appear to exhibit improved features as compared to the films prepared by high-temperature processing. IntroductionPotassium niobiate (KNbO 3 ) is a very promising material for surface acoustic wave (SAW) devices and high-performance bulk-wave transducers. 1 The elctromechanical coupling coefficient (k 2 ) of the surface wave in a single-crystal KNbO 3 can be as high as 53%, which is one order of magnitude larger than that of LiNbO 3 . 2 The bandwidth is about 20% and insertion losses are 2-6 dB. 2 The acoustic wave velocities in KNbO 3 are 3500-7500 m/s 3 and the temperature coefficient of frequency (TCF) ranges between 0 and 170 ppm/K depending upon crystallographic orientation. 2 The KNbO 3 exhibits large piezoelectric nonlinearity. The 45°r otated Y-cut X-propagated KNbO 3 has 25 dB larger efficiency than Y-Z LiNbO 3 ; thus the KNbO 3 single crystal is considered as a promising material for SAW elastic convolvers with super high efficiency and process gain. 4 In addition to excellent piezoelectric properties, the KNbO 3 has a large electrooptic coefficient, high nonlinear optical coefficient, and excellent photorefractive characteristics 5 that make it a very promising candidate for optical applications such as optical waveguides, frequency doublers, 6 intensity modulators, 7

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Section: Introductionmentioning

confidence: 99%

“…The coating had multiple cracks and did not provide complete surface coverage . Wu et al , reported hydrothermal−electrochemical synthesis of thin films of a related material, K 2 Ta 2 O 6 , with a pyrochlore structure. The pyrocholore K 2 Ta 2 O 6 films were polycrystalline with a random orientation.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Potassium Niobiate (KNbO₃) Thin Films by Low-Temperature Hydrothermal Epitaxy

Suchanek

2004

Chem. Mater.

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“…Potassium tantalate can be obtained by several methods such as chemical solution deposition, 1) sintering or calcining 2) and hydrothermal process. [3][4][5][6] In recent years, a hydrothermal electrical synthesis method is used well in the creation technology of the thin film for electronic material such as a capacitor. This method is used in supercritical or subcritical condition with an aqueous solution at the temperature of 374 C or over.…”

Section: Introductionmentioning

confidence: 99%

“…On the other hand, hydrothermal synthesis in the condition of a low temperature such as C is called mild hydrothermal synthesis method, 7) the nanocrystals were fabricated using this method. [8][9][10] This synthesis method belongs to called soft solution processing, [4][5][6] concerning the fabrication of pure, shaped, sized and oriented ceramic materials in a solution.…”

Section: Introductionmentioning

confidence: 99%

Preparation of Pyrochlore Potassium Tantalate Thin Films on Ta/ITO Glass via Mild Hydrothermal Growth

2010

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Potassium tantalate with perovskite structure (KTaO 3 ) is an incipient ferroelectric material that has promising functions in electromechanical and sensing sectors. Potassium tantalate with pyrochlore structure (K 2 Ta 2 O 6 ) appears promising in a photocatalystic field. Potassium tantalate powders and bulks were fabricated at high temperature such as over 400 C from Ta 2 O 5 and KOH. A sheet of tantalum was hard to react with potassium hydroxide in the mild hydrothermal condition at 100-150 C and low alkaline concentrations (0-2 M). Pyrochlore potassium tantalate film was synthesized with a mild hydrothermal method (100-150 C) at short reaction time by using a sputtered tantalum substrate on ITO glass. Synthesis of this film employed significantly low concentrations of KOH solution (0.1-1 M). The potassium tantalate film fabricated by the hydrothermal condition of 0.5 M-KOH solution, 100 C and 3 h reaction time was a smooth surface and became transparent. The particle size of this film was 150 nm.

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“…One of the authors previously reported the successful formation of potassium tantalate thin films with pyrochlore structure by hydrothermal−electrochemical synthesis. , In this study, sodium tantalate thin films with a single phase of pyrochlore-type Na 2 Ta 2 O 6 or NaTaO 3 with perovskite structure were fabricated directly by the hydrothermal−electrochemical method through reaction between tantalum substrate and sodium hydroxide solution. It is the first report to prepare the perovskite-type NaTaO 3 thin films without any other phase.…”

Section: Introductionmentioning

confidence: 99%

Preparation and Characterization of Sodium Tantalate Thin Films by Hydrothermal−Electrochemical Synthesis

et al. 2005

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Crystalline sodium tantalate thin films with pyrochlore (Na2Ta2O6) and perovskite (NaTaO3) structures are successfully synthesized on Ta metal substrates by a hydrothermal−electrochemical method at low temperature (≤473 K). The phase, film thickness, and domain size of the synthesized films are shown to be controllable by appropriate adjustment of the reaction conditions. Film formation mechanisms for both Na2Ta2O6 and NaTaO3 are proposed based on the experimental results.

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Untitled

Cited by 12 publications

References 32 publications

Synthesis of Potassium Niobiate (KNbO₃) Thin Films by Low-Temperature Hydrothermal Epitaxy

Synthesis of Potassium Niobiate (KNbO₃) Thin Films by Low-Temperature Hydrothermal Epitaxy

Preparation of Pyrochlore Potassium Tantalate Thin Films on Ta/ITO Glass via Mild Hydrothermal Growth

Preparation and Characterization of Sodium Tantalate Thin Films by Hydrothermal−Electrochemical Synthesis

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Untitled

Cited by 12 publications

References 32 publications

Synthesis of Potassium Niobiate (KNbO3) Thin Films by Low-Temperature Hydrothermal Epitaxy

Synthesis of Potassium Niobiate (KNbO3) Thin Films by Low-Temperature Hydrothermal Epitaxy

Preparation of Pyrochlore Potassium Tantalate Thin Films on Ta/ITO Glass via Mild Hydrothermal Growth

Preparation and Characterization of Sodium Tantalate Thin Films by Hydrothermal−Electrochemical Synthesis

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Synthesis of Potassium Niobiate (KNbO₃) Thin Films by Low-Temperature Hydrothermal Epitaxy

Synthesis of Potassium Niobiate (KNbO₃) Thin Films by Low-Temperature Hydrothermal Epitaxy