Search results for: Takamasa Sugawara

Items from 1 to 14 out of 14 results

article

Scintillation properties of a La, Lu-admix gadolinium pyrosilicate crystal

Shunsuke Kurosawa, Toetsu Shishido, Akira Suzuki, Takamasa Sugawara, more

Nuclear Instruments and Methods in Physics Research Section A: Accelerators,... > 2015 > 784 > C > 115-118

In order to obtain new scintillator with higher effective atomic number, a pyrosilicate crystal with a composition (Ce_0.01, Gd_0.54, La_0.25, Lu_0.20)₂Si₂O₇ (Ce:LaLu-GPS) was grown by the floating zone method. Emission wavelengths of this material were at 370 and 390nm. Gamma-ray-excited pulse height and scintillation decay measurement showed that Ce:LaLu-GPS had a light output of 34,000±2000 photons/MeV,...

article

Luminescence study on Eu or Tb doped lanthanum–gadolinium pyrosilicate crystal

Shunsuke Kurosawa, Toetsu Shishido, Takamasa Sugawara, Akiko Nomura, more

Optical Materials > 2015 > 41 > C > 80-83

(Eu_0.01, Gd_0.90, La_0.09)₂Si₂O₇ (Eu:La–GPS) and (Tb_0.01, Gd_0.9₀, La_0.09)₂Si₂O₇ (Tb:La–GPS) crystals were grown by the floating zone method, and their optical and scintillation properties were investigated. Gd³⁺-to-Tb³⁺ or –Eu³⁺ energy transfer processes were found, and photo-luminescence and radio-luminescence emission spectra showed ⁵D₀–⁷F_i (i=1–4) Eu³⁺ transitions in Eu:La–GPS, and ⁵D₃–⁷F_i (i=3–6)...

article

Scintillation properties of Ce:(La,Gd)2Si2O7 at high temperatures

Shunsuke Kurosawa, Toetsu Shishido, Takamasa Sugawara, Akiko Nomura, more

Nuclear Instruments and Methods in Physics Research Section A: Accelerators,... > 2015 > 772 > C > 72-75

Temperature dependence of scintillation properties was investigated for (Ce_0.01, Gd_0.90, La_0.09)₂Si₂O₇ grown by floating zone method. The light output over 35,000 photons/MeV was found constant in the temperature range from 0°C to 150°C. In addition, FWHM energy resolution of Ce:La-GPS (roughly 7–8%) at 662keV remained constant up to 100°C. Thus, this crystal can be applied to oil well logging or...

article

High-temperature elastic anisotropy of B2-type FeAl

Mi Zhao, Kyosuke Yoshimi, Junya Nakamura, Kunio Yubuta, more

Scripta Materialia > 2014 > 82 > C > 37-40

The electromagnetic acoustic resonance method was applied to measure the elastic constants (c₁₁, c₁₂, and c₄₄) of Fe–40, –43 and –46Al (at.%) single crystals from room temperature to 1173K. The temperature dependence of the energy factor, K, and the elastic anisotropy factor, A, was obtained. A increased monotonously with increasing temperature and reached ∼7 at ∼1200K. Therefore, it was confirmed...

article

Crystal growth and optical properties of Ce:(La,Gd)2Ge2O7 grown by the floating zone method

Shunsuke Kurosawa, Toetsu Shishido, Takamasa Sugawara, Kunio Yubuta, more

Journal of Crystal Growth > 2014 > 393 > C > 142-144

Some pyrosilicate scintillators such as Ce:Gd₂Si₂O₇ and Ce:Lu₂Si₂O₇ have a good light output, and especially Ce:(Gd,La)₂Si₂O₇ has an excellent light output of over 36,000ph/MeV. In order to search novel scintilators, we have developed a pyrogermanate-based scintillation material (Ce_0.01,Gd_0.90,La_0.09)₂Ge₂O₇ using the floating zone method. Although the light output was decreased due to quenching, 5d–4f...

article

Valence state of dopant and scintillation properties of Ce-doped Sr3Y(BO3)3 crystal

Rayko Simura, Shohei Kawai, Kazumasa Sugiyama, Takayuki Yanagida, more

Journal of Crystal Growth > 2013 > 362 > Complete > 296-299

A transparent Ce:SYB crystal was grown by employing the floating zone method in a dry-air atmosphere, and the growth rate was 1mm/h. The feed/seed rods were formed by sintering raw powder at 1000°C for 24h. The Ce content in the grown crystal was measured by electron probe microanalysis and was found to be very low (approximately 0.1at%). Ce LIII XANES measurement showed that 90% of the Ce in the...

article

Characterization of transparent and conducting Sn-doped β-Ga2O3 single crystal after annealing

Shigeo Ohira, Norihito Suzuki, Naoki Arai, Masahiko Tanaka, more

Thin Solid Films > 2008 > 516 > 17 > 5763-5767

Sn-doped β-Ga ₂ O ₃ single crystals with (100) plane were grown using the floating zone method, and the effect of the thermal annealing on the surface morphology, and electrical and optical properties was examined to compared with that before annealing. It was found that the surface morphology and roughness, electrical properties and optical transmittance did not change after annealing...

article

X-ray photoelectron spectroscopic studies on initial oxidation of iron and manganese mono-silicides

Naofumi Ohtsu, Masaoki Oku, Akiko Nomura, Takamasa Sugawara, more

Applied Surface Science > 2008 > 254 > 11 > 3288-3294

Initial oxidation of iron and manganese mono-silicides (FeSi and MnSi) surfaces was studied by X-ray photoelectron spectroscopy (XPS). Clean surfaces of these silicides were prepared by fracturing in an ultra high vacuum, and then the fractured surfaces were oxidized by exposing to high-purity oxygen at pressures up to 1.3Pa. For the clean FeSi surface, positive chemical shifts of the Fe 2p _3/2...

chapter

Spontaneous Modification of Grain Boundary Configuration and its Application for Realization of Bulk Multicrystalline Si with Electrically Inactive Grain Boundaries

Noritaka Usami, Kentaro Kutsukake, Takamasa Sugawara, Kozo Fujiwara, more

2006 IEEE 4th World Conference on Photovoltaic Energy Conference > 1 > 960 - 963

Conference Record of the 2006 IEEE 4th World Conference on Photovoltaic Energy Conversion

We utilized bi-crystals with an artificially designed grain boundary configuration as a seed for floating-zone growth of multicrystalline Si (mc-Si) in order to clarify the impact of the initial grain boundary configuration on the crystal growth. Intentionally introduced large tilt deviation from Sigma3 was found to lead to appearance of new crystal grains accompanied by spontaneous modification of...

article

Fabrication of hexagonal GaN on the surface of β-Ga2O3 single crystal by nitridation with NH3

Shigeo Ohira, Masayuki Yoshioka, Takamasa Sugawara, Kazuo Nakajima, more

Thin Solid Films > 2006 > 496 > 1 > 53-57

The fabrication of GaN on the surface of a bulk β-Ga ₂ O ₃ single crystal by nitridation with NH ₃ was investigated for the purpose of using it as a substrate for GaN epitaxial growth. A β-Ga ₂ O ₃ single crystal was prepared using a floating zone furnace with double ellipsoidal mirrors, and its polished (100) plane was nitridated in NH ₃ atmosphere...

article

Synthesis and structural investigation of β-Ga2O3 nanosheets and nanobelts

Shigeo Ohira, Takamasa Sugawara, Kazuo Nakajima, Toetsu Shishido

Journal of Alloys and Compounds > 2005 > 402 > 1-2 > 204-207

Nanoscale-sized sheets and belts of β-type gallium sesqui-oxide (β-Ga ₂ O ₃ ) have been successfully synthesized by a simple thermal heating method using poly- and single crystalline β-Ga ₂ O ₃ materials in Ar atmosphere under normal pressure. Synthesized products are single crystalline with monoclinic β-Ga ₂ O ₃ structure (space group: C2/m). Morphology...

article

Growth of multicrystalline Si with controlled grain boundary configuration by the floating zone technique

Masayuki Kitamura, Noritaka Usami, Takamasa Sugawara, Kenrato Kutsukake, more

Journal of Crystal Growth > 2005 > 280 > 3-4 > 419-424

The floating zone technique was employed to grow multicrystalline Si with controlled grain boundary configuration. Purposely designed bi-crystals were utilized as seed crystals to investigate the effect of the tilt angle from the perfect twin boundary on the growth behavior. When the growth was initiated from a bi-crystal with a Σ3 twin boundary, no particular change took place on the grain boundary...

article

Boron-carbon atomic ratio dependence on the hardness and oxidation resistance of perovskite-type solid solution ScRh ₃ B _x C ₁ _- _x

Toetsu Shishido, Jinhua Ye, Kunio Kudou, Shigeru Okada, more

Journal of Alloys and Compounds > 2004 > 375 > 1-2 > 217-220

Perovskite-type ScRh ₃ B and ScRh ₃ C form a continuous solid solution, ScRh ₃ B _x C ₁ _- _x , in the full range of 0 x 1 with cubic structure (space group: Pm3m, Z=1). The microhardness of the ScRh ₃ B _x C ₁ _- _x phase increases with increasing boron content. Thermogravimetric analysis of this phase indicates that the...

article

Solid solution range of boron, microhardness and oxidation resistance of the perovskite type RERh ₃ B _x (RE=Gd, Y, Sc) compounds

Toetsu Shishido, Jinhua Ye, Kunio Kudou, Shigeru Okada, more

Journal of Alloys and Compounds > 1999 > 291 > 1-2 > 52-56

Polycrystalline samples of RERh ₃ B _x (RE=Gd, Y, Sc), which consists of a reactive RE and high melting point Rh and B elements, are successfully synthesized by the arc melting method. RERh ₃ B _x compounds have the perovskite type cubic structure (space group Pm3m). Perovskite type phases of GdRh ₃ B _x and YRh ₃ B _x exist in the range...

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