Author
Hirotsugu Takizawa
Other affiliations: Akita University
Bio: Hirotsugu Takizawa is an academic researcher from Tohoku University. The author has contributed to research in topics: Microwave & Crystal structure. The author has an hindex of 23, co-authored 180 publications receiving 1989 citations. Previous affiliations of Hirotsugu Takizawa include Akita University.
Papers published on a yearly basis
Papers
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TL;DR: In this article, a multi-mode microwave heating system operating at a frequency of 28 GHz was used to produce rapid synthesis of well-sintered TiO 2 nanocrystalline thin film on transparent conductive PET-ITO electrode.
Abstract: Microwave preparation of TiO 2 nanocrystalline electrode for use in dye-sensitized solar cells is examined. A multi-mode microwave heating system operating at a frequency of 28 GHz is used to produce rapid synthesis. Well-sintered TiO 2 nanocrystalline thin film is successfully fabricated on transparent conductive PET–ITO electrode. Photoelectron energy conversion efficiency of 2.16% is achieved in an electrode prepared by 28 GHz microwave irradiation at 1.0 kW for 5 min.
149 citations
TL;DR: By a solid state reaction of LaN, Eu 2 O 3 and Si 3 N 4, LaSi 3 N 5− X O X and LaEuSi 2 N 3 O 2, these compounds were identified by X-ray diffraction analysis, and then characterized by means of absorption and luminescence spectroscopies.
94 citations
TL;DR: In this article, the electrical properties of (R{sub 1-x}Ca{sub x})MnO{sub 3-{delta}} (R: Tb, Ho, Y) solid solutions with the orthorhombic perovskite-type structure were synthesized and their electrical resistivity and thermoelectric power were measured in the temperature range 80 to 1000 K.
92 citations
82 citations
TL;DR: In this article, the cubic B20 structure of MnGe and CoGe was synthesized at 4.5 GPa and 600-1000°C for 1-3 hr using the belt-type high-pressure apparatus.
67 citations
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9,432 citations
TL;DR: Dye-sensitized solar cells (DSCs) offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency as mentioned in this paper, and many DSC research groups have been established around the world.
Abstract: Dye-sensitized solar cells (DSCs) offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency. DSC research groups have been established around the worl ...
8,707 citations
TL;DR: The trivalent europium ion (Eu3+) is well known for its strong luminescence in the red spectral region, but this ion is also interesting from a theoretical point of view as mentioned in this paper.
1,906 citations
TL;DR: In this article, the most recent advances in the synthesis and application of phosphors for white light-emitting diodes (pc-WLEDs) with emphasis specifically on: (a) principles to tune the excitation and emission spectra of the phosphors: prediction according to crystal field theory, and structural chemistry characteristics (e.g. covalence of chemical bonds, electronegativity, and polarization effects of element); (b) pc-W LEDs with phosphors excited by blue-LED chips: phosphor characteristics, structure, and activated ions
Abstract: Phosphor-converted white light-emitting diodes (pc-WLEDs) are emerging as an indispensable solid-state light source for the next generation lighting industry and display systems due to their unique properties including but not limited to energy savings, environment-friendliness, small volume, and long persistence. Until now, major challenges in pc-WLEDs have been to achieve high luminous efficacy, high chromatic stability, brilliant color-rending properties, and price competitiveness against fluorescent lamps, which rely critically on the phosphor properties. A comprehensive understanding of the nature and limitations of phosphors and the factors dominating the general trends in pc-WLEDs is of fundamental importance for advancing technological applications. This report aims to provide the most recent advances in the synthesis and application of phosphors for pc-WLEDs with emphasis specifically on: (a) principles to tune the excitation and emission spectra of phosphors: prediction according to crystal field theory, and structural chemistry characteristics (e.g. covalence of chemical bonds, electronegativity, and polarization effects of element); (b) pc-WLEDs with phosphors excited by blue-LED chips: phosphor characteristics, structure, and activated ions (i.e. Ce 3+ and Eu 2+ ), including YAG:Ce, other garnets, non-garnets, sulfides, and (oxy)nitrides; (c) pc-WLEDs with phosphors excited by near ultraviolet LED chips: single-phased white-emitting phosphors (e.g. Eu 2+ –Mn 2+ activated phosphors), red-green-blue phosphors, energy transfer, and mechanisms involved; and (d) new clues for designing novel high-performance phosphors for pc-WLEDs based on available LED chips. Emphasis shall also be placed on the relationships among crystal structure, luminescence properties, and device performances. In addition, applications, challenges and future advances of pc-WLEDs will be discussed.
1,860 citations
TL;DR: The response of the worldwide scientific community to the discovery in 2008 of superconductivity at T c'='26'K in the Fe-based compound LaFeAsO1−x F x has been very enthusiastic.
Abstract: The response of the worldwide scientific community to the discovery in 2008 of superconductivity at T c = 26 K in the Fe-based compound LaFeAsO1−x F x has been very enthusiastic. In short order, ot...
1,373 citations