Flux Growth of KNbO3 Crystals by Pulling-Down Method
TL;DR: In this paper, the micro-pulling-down method was used to grow transparent, transparent, and crack-free KNbO 3 crystals from the melts containing excess of K 2 O as a flux.
Abstract: The crystals of KNbO 3 have been grown by the micro-pulling-down method. Colorless, transparent, and crack-free crystals were produced from the melts containing excess of K 2 O as a flux. Growth of relatively large size (up to 2 mm in diameter and up to 30 mm in length) single crystals was found is possible using the crucibles with corresponding nozzle size (up to 2.0 mm in outer diameter). Second harmonic generation was observed in the crystals irradiated by fundamental beam with wavelength about 860 nm.
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TL;DR: The micro-pulling-down technique is a crystal growth method that has been mostly developed since 1992 as mentioned in this paper, where the melt (oxide, fluoride, metal) residing in a crucible is transported in downward through microcapillary channel(s) made in the bottom of the crucible.
Abstract: The micro-pulling-down technique is a crystal growth method that has been mostly developed since 1992. The general scheme of the growth system is relatively simple: the melt (oxide, fluoride, metal) residing in a crucible is transported in downward through microcapillary channel(s) made in the bottom of the crucible. Two driving forces (capillary action and gravity) support the delivery of the melt to the liquid/solid growth interface formed under the crucible due to a properly established temperature gradient. Appropriate configuration of the crucible bottom allows for controlling of the crystal shape (fibers, rods, tubes, plates) and the dimensions of the crystals' cross sections that range approximately from 0.1 to 10 mm. A great number of scientifically and industrially important optical crystal fibers have been successfully produced using this method.
70 citations
TL;DR: In this article, the largest crystals of this family of compounds were grown by hydrothermal methods to date, and the reaction was designed to provide homogeneous distribution of tantalum and niobium metal centers throughout the KTN lattice to maximize its electro-optic properties.
26 citations
01 Jan 2015
TL;DR: In this article, the growth of single crystals from low- and high-temperature solutions is discussed, and various modern methods for growing bulk single crystals are described, as well as new approaches to explain the dependence of metastable zone width on various factors.
Abstract: Fundamental aspects of the growth of single crystals from low- and high-temperature solutions are reviewed. Different modern methods for growing bulk single crystals from low- and high-temperature solutions are described. New approaches to explain the dependence of metastable zone width on various factors, effects of impurities on growth rates and growth morphology of crystals, and determination of growth mechanisms from experimental data on growth kinetics are discussed. The nature of supersaturation barriers observed during the growth of single crystals from aqueous solutions containing impurities are briefly described. Analysis of the effects of organic molecules and inorganic nanoparticles on the crystallization behavior of some inorganic and semiorganic salts is also presented. For the growth of crystals from high-temperature solutions, an overview of suitable solvents for growth, properties of high-temperature solvents, and methods for the growth and characterization of single crystals are given.
23 citations
TL;DR: The KN film exhibited a bipolar resistive switching behavior with good reliability characteristics that can be explained by the formation and rupture of the oxygen vacancy filaments, and can be used for self-powered biomedical devices.
Abstract: Amorphous KNbO3 (KN) film containing KN nanocrystals was grown on TiN/SiO2/Si substrate at 350 °C. This KN film showed a dielectric constant (er) and a piezoelectric strain constant (d33) of 43 and 80 pm/V at 10 V, respectively, owing to the existence of KN nanocrystals. Piezoelectric nanogenerators (PNGs) were fabricated using KN films grown on the TiN/polyimide/poly(ethylene terephthalate) substrates. The PNG fabricated with the KN film grown at 350 °C showed an open-circuit output voltage of 2.5 V and a short-circuit current of 70 nA. The KN film grown at 350 °C exhibited a bipolar resistive switching behavior with good reliability characteristics that can be explained by the formation and rupture of the oxygen vacancy filaments. The KN resistive random access memory device powered by the KN PNG also showed promising resistive switching behavior. Moreover, the KN film shows good biocompatibility. Therefore, the KN film can be used for self-powered biomedical devices.
22 citations
TL;DR: In this article, the diameter self-control was established in Bi4Ge3O12 fiber crystal growth by micro-pulling-down technique, in which the diameter was controlled due to compensation of solidification with evaporation of volatile Bi2O3 selfflux charged into the crucible with excess.
Abstract: Diameter self-control was established in Bi4Ge3O12 fiber crystal growth by micro-pulling-down technique. In accordance with Bi2O3-GeO2 phase diagram, the diameter was controlled due to compensation of solidification with evaporation of volatile Bi2O3 self-flux charged into the crucible with excess. The crucibles had capillary channels of 310 or 650 μm in outer diameter. The crystals up to 400 mm long and 50-300 μm in diameter were grown at pulling-down rates of 0.04-1.00 mm/min. The melt composition and the pulling rate were generally only two parameters determining solidification rate. As a result, crystals with uniform (± 10%) diameter and aspect ratio up to 104 were produced without automation of the process. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
22 citations
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TL;DR: LiNbO 3 micro single crystals were succesfully grown by a crystal growth method using a micro nozzle in the bottom of a crucible as discussed by the authors, and the grown crystals were revealed to be free of dislocations and subgrain boundaries up to 500 μ m in diameter.
182 citations
TL;DR: In this paper, a top-seeded pulling procedure based on a defined powder synthesis of KNbO 3, a revision of the K 2 O-Nb 2 O 5 phase diagram, a study of the exchange between crystal and melt via gas phase and the description of the apparatus used are reported.
99 citations
TL;DR: In this article, a modified Kyropoulos technique is applied to obtain large single domain KNbO3 crystals suitable for optical applications, up to 30×30×15 mm3 in size with 52~55 mole% K2CO3 content under the condition of shallow temperature gradient.
Abstract: A modified Kyropoulos technique is applied to obtain large single domain KNbO3 crystals suitable for optical applications. Colorless and high resistivity crystals up to 30×30×15 mm3 in size are grown with 52~55 mole% K2CO3 content under the condition of shallow temperature gradient. Single domain crystals up to 8 mm cube are obtained through poling procedure with a d-c field of approximately 1 kV/cm at about 190°C under slight stress along an a axis. The poled crystals are found to be of good optical quality by microscopic examination with polarized light and experiments on second harmonic generation using 1.06 µCW Nd:YAG laser. The second harmonic efficiency for up-conversion of KNbO3 is found to be as high as that of Ba2NaNb5O15. KNbO3 is revealed to be a potentially useful non-linear material for optical device application.
66 citations
TL;DR: In this article, the Nb 2 O, Na 2 O and K 2 O systems were re-investigated between 50 and 100 mol% by thermal analysis, dilatometry and X-ray techniques.
52 citations
TL;DR: In this article, the effects that are produced in oxides as a result of high temperature equilibration processes are examined by x-ray, neutron and electron diffraction and how these effects change under changing thermal conditions.
51 citations