Nobuaki Terakado

Nobuaki Terakado
Tohoku University | Tohokudai · Department of Applied Physics

Doctor of Engineering

About

58
Publications
3,550
Reads
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444
Citations
Introduction
1. Dynamic control of heat/temperature using magnons for advanced thermal management. 2. Strengthened glass: mechanism & evaluation. 3. High thermal conductivity glass: MgO-oversupply method & development. 4. Methods: melt-quenching, sputtering, solid state reaction, XRD, Raman spectroscopy, thermorefrectance, etc.
Additional affiliations
April 2011 - March 2014
A venture company
Position
  • Senior Researcher
Description
  • Development of new types of batteries and electric paper
Education
April 1998 - September 2007
Hokkaido University
Field of study
  • Applied Physics

Publications

Publications (58)
Article
Full-text available
Photoluminescence provides information about the surrounding environment. In this study, aiming to develop a non-invasive deep body-temperature sensing method, we investigated photoluminescence properties of afterglow zirconia (ZrO2) by pulsed near-infrared (NIR) light irradiation based on the biological temperature. Pulsed light irradiation produc...
Article
Noninvasive and site-selective temperature sensing is required in biology and advanced medicine. Recently, we proposed a new concept for temperature sensing, which is based on afterglow and optically-stimulated luminescence [Sci. Rep. 10, 2242 (2020)]. Here we assessed the thermal sensitivity of afterglow zirconia and clarified the potential of thi...
Article
Full-text available
Dynamic control of heat flow for applications in thermal management has attracted much interest in fields such as electronics and thermal engineering. Spin-chain ladder cuprates are promising materials to realize dynamic control of heat flow, since their magnon thermal conductivity is sensitive to the hole density in the spin ladders, which can be...
Article
Full-text available
Oxide glass is an industrial material with advantages such as optical transparency and shaping ability of the melt, but at the same time, it is a bad conductor of heat due to its disordered structures. Therefore, heat dissipation in glass components often becomes a problem and its applications to the thermal management has been limited to use as a...
Article
Optical modulation based on second-order optical nonlinearity is required to control a light-wave for telecommunication with optical-fiber network, and the controlling device is basically constructed using a single crystal material. To fabricate an optical device material having the connectivity to glass fiber, glass-ceramic (GC) processing is effe...
Article
Full-text available
Chemically strengthened glass is widely used for screen protection in mobile devices, and its strengthening processes and application fields have rapidly diversified. The origin of the strength is residual compressive stress induced by ion exchange, and the stress evaluation has been performed via the photoelastic effect. However, for a deep unders...
Article
Full-text available
Phase change material (PCM), which enables heat storage based on phase transition, plays an important role for efficient energy utilization. This paper briefly describes our recent study about all-solid PCM by combination of vanadium dioxide (VO2) with latent heat storage capacity and multicomponent glass, i.e., VO2-dispersed glass. A B2O3-P2O5-V2O...
Article
Full-text available
Development of minimally invasive and site-selective biological temperature sensing is quite important in medical field. This study presents a novel temperature sensing technique based on afterglow and optically-stimulated luminescence (OSL). The dependence of afterglow photoluminescent intensity on the environmental temperature of zirconia (ZrO2)...
Conference Paper
We have investigated atomic-scale structures in 2-step ion-exchanged strengthened glasses by using polarized micro-Raman spectroscopy for non-destructive evaluation of the compressive stress.
Article
This study describes the investigation of photoluminescence (PL) and afterglow properties of samarium ion (Sm³⁺)-doped zirconia and the comparison with those of pure zirconia. The pure sample exhibits bluish PL and afterglow upon excitation by ultraviolet light, whereas white-to-reddish PL and white afterglow are detected by means of visual observa...
Article
We have fabricated perfectly-surface-crystallized glass-ceramics (PSC-GCs) consisting of polar frenoite-type Sr 2 TiSi 2 O 8 by different crystallization-process conditions, i.e., isothermal treatment at 880 °C for 72 h and 960 °C for 1 h, and have examined their Pockels effect in this study. The PSC-GCs obtained by the lower-temperature process ex...
Article
Materials with high thermal conductivity have attracted considerable attention for thermal management of electronic devices. Therefore, focusing on formability and anisotropic heat transfer, we fabricated glass-ceramics containing the spin-chain compound SrCuO2 and demonstrated its high thermal conductivity in the previous work, where SrCuO2 is kno...
Article
Oxide glasses generally have low thermal conductivity due to their disordered structures. Here, a fabrication method to provide them with high thermal conductivity while retaining their optical transparency is proposed. It consists of dispersing ∼20 μm MgO crystals in a glass matrix and matching their refractive indexes to prevent the decrease of t...
Article
We investigated the long-lasting photoluminescence (LLP) properties in a commercial zirconia powder with a monoclinic system after thermal treatment at different temperatures. Clear-blue photoluminescence and LLP were observed in the zirconia without emissive dopants subjected to thermal treatment at 1400 °C. Decay curve measurements revealed a pro...
Article
Full-text available
Energy storage technology is crucial for a sustainable society, and its realisation strongly depends on the development of materials. Oxide glass exhibits high durability. Moreover, the amorphous structure of the glass without periodic ordering demonstrates excellent formability and controllability, thus enabling a large-scale production. These fac...
Article
We investigated the Pockels effect in polycrystalline materials consisting of highly oriented polar fresnoite-type Sr2TiSi2O8 fabricated using perfectly surface-crystallized glass-ceramics (PSC-GCs). The chemical composition of the precursor glass was shown to significantly affect the crystallized texture, e.g., the crystal orientation and appearan...
Conference Paper
We fabricated the highly-oriented glass-ceramics in silicate systems, and succeeded in estimating the Pockels and second-order nonlinear optical constants comparable to common inorganic nonlinear-optical crystals.
Conference Paper
We fabricated the glass-ceramic fiber with nonlinear-optical crystal, which is radially-crystallized. Visible second-harmonic generation and its intensity-independence on the fundamental polarization were demonstrated.
Conference Paper
Creation of polar Sr2TiSi2O8 crystal was attempted by CO2 laser-irradiation on the glass surface, aiming to control of the crystal-domain structure, and the second-harmonic generation was clearly observed in the laser-crystallized region.
Article
We fabricated glass-ceramics composed of emissive nanocrystals that show variation in photoluminescence coloration. The change in emission color is based on the amorphous-to-crystalline phase transformation in a Mn-containing zincogermanate glass. The transformation occurred at a 50 °C temperature range (538–588 °C), resulting in a change in photol...
Article
Recently, we have developed the borosilicate glass, in which ZrO2 phase is singly crystallizable, and has found an emissive monoclinic ZrO2 dendrites in the resulting GCs. In order to promote the formation of monoclinic phase, we have examined the effect of substitution of alumina Al2O3 for ZrO2 in the precursor glass composition, i.e., 15Na2O-(15-...
Article
Chemically strengthened glass has become essential in our daily lives and the demand is rapidly increasing in a variety of fields. However, the conventional cutting process is not applicable because of its tough layer with the compressive stress. To achieve higher-throughput production of the glass, we report spatially selective weakening of the co...
Article
The control of heat flow has become increasingly important in energy saving and harvesting. Among various thermal management materials, spinon thermal conductivity materials are promising for heat flow control at microscales because they exhibit high, anisotropicthermal conductivity resulting from spin chains. However, there has been only little de...
Article
We prepared SrCuO2 thin film by radio-frequency magnetron sputtering on glass substrate and have investigated its post-annealing effects on structure and thermal conductivity. The as-sputtered film belongs to two-dimensional spin system SrCuO2, namely, layer-type SrCuO2, which has a possibility of exhibiting high, anisotropic thermal conductivity b...
Article
Functional nanocrystals have received considerable attention because of their various applications. Although glass-ceramic (GC) processing is recognized as promising for preparation of nanostructured material, it is difficult to use the materials as nanocrystals as in. This study provides a possible way to obtain nanocrystals by irradiation of fund...
Article
We prepared a borosilicate glass, in which the ZrO2 phase is singly crystallizable, i.e., 15Na2O–15ZrO2–30B2O3–40SiO2 glass, and investigated the texture and morphology of the resulting glass-ceramics. ZrO2 dendrites with a tetragonal system (high-temperature phase) were developed as initial phase, and the tetragonal phase was transformed to the mo...
Article
Study on visible light response of photocatalytic materials is very important research area for future energy society. Generally, in conventional photocatalysts, visible light response is provided by defect introduction. This phenomenon is based on formation of trap level between valence and conduction band. In our previous report, we have already...
Article
We performed depth analysis of a compression layer in Corning Gorilla Glass 3, one of commercialized chemically-strengthened glasses, using depth-resolved micro-Raman spectroscopy. We obtained a depth variation of Raman spectra and an ion-exchange rate of Na for K was determined by energy dispersive X-ray spectroscopy.We found that a peak position...
Article
We have synthesized spinon thermal conductivity materials in Sr–Cu–O system by glass-ceramics technique. The materials are promising for active control of thermal energy in microelectronic devices because of high and anisotropic thermal conduction, its controllability, and electric insulation. Nevertheless, research on these materials has been limi...
Article
We prepared SrCuO2 film by radio-frequency magnetron sputtering on silica glass and have investigated structure change induced by super-band-gap light. An X-ray diffraction pattern shows that the as-sputtered film is composed of (001)-oriented SrCuO2 nanothick crystals belonging to tetragonal system, i.e., the layer-type SrCuO2. Raman-scattering sp...
Article
Full-text available
We have synthesized Mn4+-doped mixed tetragermanate phases in the Li2Ge4O9LiNaGe4O9 system, i.e., Li(Li,Na)Ge4O9, by a glass-ceramic technique using stoichiometric precursor glasses, and have examined the effect of substitution of Na on their photoluminescence properties. The tetragermanate phases indicated clear red emission based on a 2E→4A2 tran...
Article
We examined the crystallization and crystal growth of ZnO in the viscoelastic supercooled liquid (SCL) phase based on microscopic and spectroscopic observations. The resulting glass–ceramics exhibits complex ZnO dendrites that precede the formation of Zn-rich regions because of phase separation. Compressive stresses are concentrated at the interfac...
Article
We compare the boson peaks (BPs) observed in low-frequency Raman scattering with the BPs observed in low-temperature specific heat in many oxide glasses. We find a linear correlation of the maximum positions between the Raman BP and specific-heat BP regardless of the constituents. In addition, we show that several chalcogenide and molecular glasses...
Article
Full-text available
Silicate glass has been used for long time because of its advantages from material's viewpoint. In this paper, we report the observation of Pockels effect by Mach-Zehnder interferometer in polycrystalline ceramics made from a ternary silicate glass via crystallization due to heat-treatment, i.e., glass-ceramics. Since the silicate system is employe...
Article
We prepared SnOZnOB2O3 system glasses by means of melt-quenching technique with different melting-process temperatures in range of 11001500 °C, and examined the impact of the process temperature on photoluminescent (PL) property. The glass obtained at 1100°C showed clear PL band at ∼2.8 eV at room temperature. As elevating the process temperature,...
Article
We assessed the photoluminescence performance characteristics of Mn4+-doped tetragermanate and silicogermanate phases with a benitoitetype structure. We observed a visible red emission based on the 2E→4A2 transition in the doped benitoite-type tetragermanate. The partial substitution of Si for Ge, resulting in SrGe3.495Mn0.005Si0.5O9, improved the...
Article
High thermal conductivity materials are in great demand for heat-flow control and heat dissipation in electronic devices. In this study, we have produced a glass-ceramics that contains spin-chain compound SrCuO2 and have found that the glass-ceramics yields high thermal conductivity of ∼5 W K−1 m−1 even at room temperature. The glass-ceramics is fa...
Article
Full-text available
The authors aim to report the largest enhancement of photocatalytic activity by chemical etching in anatase-type TiO2 crystallized glass. Optimization of several conditions for crystallization behavior and chemical etching to realize the nano-structured ceramics (NSC) has been performed in the crystallized glass. NSC-fabrication by chemical etching...
Article
We synthesized the lithium-tetragermanate (Li2Ge4O9) phase doped with Mn4+ by glass-ceramics technique using the stoichiometric glass-precursor with different MnO2 concentrations, i.e., 20Li(2)O-80GeO(2)-xMnO(2) (x = 0.1-0.7), and examined their photoluminescent property. The doped phase showed clear red-emission at room temperature, and the intern...
Article
A production of polycrystalline phase with glassy precursor, i.e., glass-ceramics processing, has a great potential to fabricate the sophisticated materials. In this study, we have prepared the Bi2O3–Fe2O3–BaO–B2O3 system precursor, in which BiFeO3 phase is crystallizable, and examined the phase formation and physical properties in resulting glass-...
Article
We demonstrate that the optical transmittance of bilayer samples consisting of pyrolytically coated amorphous Mg–Sn–O and metal oxide films such as In2O3 and SnO2 decreases upon ultraviolet illumination, but can be recovered by annealing in air at ∼300 ∘C. Spectral, structural, and compositional studies suggest that this photochromic phenomenon is...
Article
Full-text available
We have fabricated a rechargeable photo-chemical battery using ion-hole conducting AgAsS2 films. An asymmetrically-electroded Al/AgAsS2/SnO2 yields photocurrents and upon illumination it is concomitantly charged up. When the illumination is stopped, the stack discharges electricity into an external circuit. This photo-charging and discharging pheno...
Article
The photodoping process in Al/AsS2/Ag tri-layer films has been studied through measurements of electrical impedance, photodoped-layer thickness, and photocurrent. Frequency dependence of the impedance suggests that the sample under photodoping can be approximated by an equivalent electrical circuit. A thickness of photodoped layers, which is estima...
Article
Two aspects of photoinduced phenomena in oxide and chalcogenide glasses have been studied. One is a comparison of irreversible, reversible, and transitory changes in As2S3, which gives insights into universal features of the photoinduced phenomenon. The other is composition dependence of structures and photodarkening in GeO2–GeS2 glasses. The depen...
Article
Semi-free As2S3 flakes undergo visible-scale anisotropic deformations when exposed to linearly-polarized bandgap illumination. We investigate the behavior and also those in amorphous Se, GeS2, AgAsS2, and crystalline As2S3. These results suggest that the deformation occurs through photo-induced birefringence, photo-induced fluidity, and optical for...
Article
Semi-free As2S3 glass flakes undergo sub-mm scale anisotropic deformation upon illumination of linearly-polarized cw bandgap light. The mechanism has been ascribed to photo-induced birefringence, optical torque, and photo-induced fluidity. Quantitative measurements demonstrate that generated optical torque is ∼10–20 Nm under a light intensity of 1...
Article
Composition dependence of Ag-photodoping in x GeO2-(100–x)GeS2 glasses has been studied. The doping rate decreases with an increase in x, and becomes negligible at x ≥ 60. This photodoping disappearance can be related with transformation from percolated GeS2 networks in the heterogeneous oxy-chalcogenide glasses to isolated nano-scale clusters. Rem...
Article
Full-text available
Atomic bonding structures in xGeO2-(100-x)GeS2 glasses have been studied through structural and chemical experiments. Atomic force microscope images in alkali-etched samples with x = 80 mol % show nano-scale dips, which are ascribable to isolated GeS2 clusters. Transmission electron microscope images and small angle X-ray scattering patterns sugges...
Article
Photoluminescence and electron-spin resonance in nano-structured GeO2 GeS2 glasses have been studied. With an increase in the GeO2 content from 0 to 80 mol %, a luminescence peak blue-shifts from 1.3 to 2.1 eV in photon energy, which is more prominent than an increase in the optical gap from 3.4 to 3.6 eV. Dark and photoinduced electron-spin signal...
Article
Full-text available
Oxy-chalcogenide glasses with compositions of xGeO2–(100−x)GeS2, where 0⩽x⩽100mol%, have been prepared and studied in terms of their structures and optical properties. X-ray fluorescence spectroscopy shows that Ge:S ratio can deviate from GeS2 by ∼10at.%, depending critically upon the preparation conditions. Raman scattering spectroscopy suggests t...
Article
The chalcogenide glass is known to exhibit prominent anisotropic deformations when illuminated by linearly-polarized bandgap light. We report new deformation phenomena for AS2S3. We also propose that many deformation phenomena can be accounted for by an optical force model.
Article
Composition dependences of glass-transition temperature, optical gap, photodarkening, and photoinduced volume change in xGeO2-(100-x)GeS2 oxy-chalcogenide glasses have been studied comparatively. The transition temperature and optical gap are nearly constant at 0
Article
Full-text available
Glass exhibits many kinds of photoinduced phenomena, among which the giant photo-expansion appearing in chalcogenide glasses such as As2S3 may be the most dramatic and promising. Its feature, mechanism, and application including micro-lenses are described.
Article
Photo-induced changes in GeO2 glass have been studied in terms of its optical and structural properties. Band-gap excitation gives rise to modifications in mid-gap optical absorption and photo-luminescence spectra. It also produces electron-spin signals at g ≃ 1.995 and 2.008. Raman-scattering spectrum becomes sharper, X-ray diffraction patterns sh...
Article
Macroscopic and microscopic changes in sputtered GeO2 films induced by band-gap light from an ArF excimer laser have been studied. When irradiated at 1 atm, the film thickness increases, surface-roughness increases, refractive-index decreases, hygroscopic enhancements, and Ge–O–Ge distance increases. Irradiations in vacuum make these changes smalle...

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Projects

Projects (2)
Project
Understanding of nano-, meso-, and macro-scale "strengthening"
Project
Development of a new device that can precisely control heat & temperature