Hokuto, Japan
Hokuto, Japan

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Watauchi S.,Yamanashi University | Abdur Razzaque Sarker M.,Yamanashi University | Nagao M.,Yamanashi University | Tanaka I.,Yamanashi University | And 2 more authors.
Journal of Crystal Growth | Year: 2012

Mirror tilting effects on the interface shape during crystal growth and on the etch pit density of the grown crystals were studied using a tilting-mirror-type image furnace. With increase of tilting angle of mirrors, convexities of both melt-feed and melt-crystal interface and the etch pit density of the grown crystal were systematically reduced. The melt zone, which is formed during crystal growth, was also stabilized by mirror tilting. In the mirror tilted condition, a large rutile single crystal of 19 mm φ diameter was successfully grown. © 2011 Elsevier B.V.


Abdur Razzaque Sarker M.,Yamanashi University | Watauchi S.,Yamanashi University | Nagao M.,Yamanashi University | Watanabe T.,Crystal Systems Co. | And 2 more authors.
Journal of Crystal Growth | Year: 2010

The effects of tilting the mirrors of a tilting-mirror-type image furnace were examined for the crystal growth of rutile by the infrared-heating floating zone (FZ) method. The mirrors were tilted from horizontal to 20° in 5° steps to examine the change of the solidliquid interface during crystal growth. The molten zone was quenched during the FZ growth. A small amount of yttrium with an extremely small segregation coefficient was added to the molten zone so that the shape of the solidliquid interface could be evaluated through the yttrium distribution. At zero degrees, the grown crystal side of the interface was highly convex with a convexity (h/r) of 0.55. The interface became less convex as the tilting angle increased. At the tilting angle of 20°, it was still slightly convex with h/r=0.20. On the other hand, the convexity of the interface on the feed side significantly decreased with increase in tilting angle; h/r changed from 0.50 at 0° to 0.00 at 20°, at which the interface was rather concave. A larger tilting angle stabilized the molten zone. Large rutile crystals of 18 mm diameter were successfully grown at a tilting angle of 10°. © 2010 Elsevier B.V.


Sarker M.A.R.,Yamanashi University | Watauchi S.,Yamanashi University | Nagao M.,Yamanashi University | Watanabe T.,Crystal Systems Co. | And 2 more authors.
Crystal Growth and Design | Year: 2010

Rutile single crystals were grown by the floating zone (FZ) method using a tilting-mirror-type image furnace. The tilting angle (θ) of the mirrors during the growth was changed from 0 to 10 and 20° to examine the effects of θ on crystal quality. The etch pit density (EPD) at the center of the crystals was low compared with that at the periphery. The EPDs at the periphery and center of the crystals grown at θ = 0° were (11-16) × 104 and 5 × 104 cm-2, respectively. Both values significantly decreased with an increase in θ. In the crystal grown at θ = 20°, the EPDs at the periphery and center were 7.9 × 104 and 1.5 × 104 cm-2, respectively. In particular, at the center of the crystals, the EPD for θ = 20° was 30% of that for θ = 0°. This result suggests that the quality of rutile crystals can be improved by tilting the focusing mirrors used in crystal growth. © 2010 American Chemical Society.


Sarker M.A.R.,Yamanashi University | Watauchi S.,Yamanashi University | Nagao M.,Yamanashi University | Watanabe T.,Crystal Systems Co. | And 2 more authors.
Physica C: Superconductivity and its Applications | Year: 2012

Large single crystals of La 2-xSr xCuO 4 (LSCO) high-T c superconductors were grown by the infrared heating floating zone (IR-FZ) method using a tilting-mirror-type image furnace. The maximum diameter of the LSCO crystals increased to 10 mm in the tilting-mirror-type image furnace from 6 mm in the conventional image furnace. CuO rich feeds were required for the crystal growth using the tilting-mirror-type image furnace to compensate for the lack of CuO caused by the significant evaporation of CuO during the growth. The evaporation of CuO was affected by the tilting angle of the mirrors of the image furnace and by feed diameter. The optimized growth conditions were as follows: mirror tilting angle, 20°; feed diameter, 10 mm∅; and feed composition 50.7 mol% CuO. © 2011 Elsevier B.V. All rights reserved.


Abdur Razzaque Sarker M.,Yamanashi University | Watauchi S.,Yamanashi University | Nagao M.,Yamanashi University | Watanabe T.,Crystal Systems Co. | And 2 more authors.
Journal of Crystal Growth | Year: 2011

The effects of the diameter of a rutile (TiO2) crystal on interface shape during TiO2 crystal growth by the floating zone (FZ) method using a tilting-mirror-type image furnace and on the etch pit density (EPD) of rutile single crystals were examined. To investigate the diameter effect on the interface shape, the grown crystal diameter was varied from 6 to 11 mm at two different tilting angles (θ) of 0° and 20°, respectively. The interface shape was characterized by the convexity (h/r) of interface, where h and r represent the height of the interface and the radius of the grown crystals. The h/r of the crystalmelt interface decreased from 0.15 to 0.0 with an increase in the crystal diameter from 6.5 to 11.2 mm at θ=20°, whereas it increased from 0.45 to 0.58 with an increase in the crystal diameter from 6.0 to 11.0 mm at θ=0°. This result suggests that the molten zone becomes stable at θ=20° for the growth of crystals with a larger diameter. To investigate the crystal diameter effect on the EPD, rutile single crystals with diameters of 10, 16 and 19 mm were grown at θ=20°. The EPDs at the center were 1.0-1.4×104 cm-2, which were much smaller than those at the periphery, i.e., 8.0-13.0×104 cm-2, for all the grown crystals with different diameters. © 2011 Elsevier B.V. All rights reserved.


Ito T.,Japan National Institute of Advanced Industrial Science and Technology | Ushiyama T.,Japan National Institute of Advanced Industrial Science and Technology | Yanagisawa Y.,Japan National Institute of Advanced Industrial Science and Technology | Tomioka Y.,Japan National Institute of Advanced Industrial Science and Technology | And 2 more authors.
Journal of Crystal Growth | Year: 2013

We have developed a laser-diode-heated floating zone (LDFZ) method, in order to improve the broad and inhomogeneous light focusing in the conventional lamp-heated floating zone method, which often causes difficulties in the crystal growth especially for the incongruently melting materials. We have simulated the light focusing properties of the LDFZ method to make the whole of the molten zone irradiated with concentrated and homogeneous laser lights. We have designed and assembled an LDFZ furnace, and have demonstrated how it works through actual crystal growth. The method is applicable to various kinds of materials, and enables stable and reproducible crystal growth even for the incongruently melting materials. We have succeeded in the crystal growth of representatives of the incongruently melting materials such as BiFeO3 and (La,Ba)2CuO4, which were believed to be difficult to be grown by the conventional method. Tolerance to the decentering of samples and highly efficient heating are also established in the LDFZ method. © 2012 Elsevier B.V. All rights reserved.


Patent
Crystal Systems Corporation, Japan National Institute of Advanced Industrial Science and Technology | Date: 2010-12-28

[Technical Problem] It is an object to provide a device for a single-crystal growth and a method of a single-crystal growth in which even when materials that are different in, for example, a melting point or a diameter are to be grown, the conditions for the stable growth of a single crystal can be obtained and a high-quality single crystal having a desired diameter can hence be grown. In addition, the device and the method have a reduced fluctuation of heating intensity to facilitate a crystal growth. [Solution of Problem] A device for a single-crystal growth is provided with a raw material rod (14) that is supported by an upper crystal driving shaft (8), a seed crystal rod (16) that is supported by a lower crystal driving shaft (12), and a heating means, and a contact part of the raw material rod (14) with the seed crystal rod (16) is heated with a heating means to form a melting zone (18) and grow a single crystal. The device is characterized in that the heating means is configured by a plurality of rectangular beams produced by lasers (2a, . . . 2e) which emit a laser light having the equivalent irradiation intensity and by an optical means, the heating means being disposed in a circumferential direction of the melting zone (18).


Patent
Crystal Systems Corporation | Date: 2010-11-03

[Abstract] This invention provides a floating zone melting apparatus in which a sample rod especially having a large diameter can be stably melted with a certainty and the crystal being grown can retain a flat shape at the interface of the solid phase and the liquid phase, whereby a single crystal having a large diameter can be grown. [Problem] It is an object to provide a floating zone melting apparatus of the infrared concentration heating type in which a sample is set in a sample chamber made of a transparent quartz tube, an atmospheric gas is introduced into the sample chamber, infrared rays emitted from a plurality of infrared ray irradiation means are converged to the sample to heat and melt the sample in this state, thereby obtaining a melt, and the melt is solidified on a seed crystal to grow a single crystal. The plurality of infrared ray irradiation means comprise a plurality of infrared ray irradiation means of the downward irradiation type that emit an infrared ray downward from an oblique upper direction and a plurality of infrared ray irradiation means of the upward irradiation type that emit an infrared ray upward from an oblique lower direction.

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