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Traditionally, the stuffing model has been used to describe stress generation in chemically strengthened glass. Nevertheless, the associated unrealistic conditions, including an imaginary volume expansion and its suppression in an adiabatic closed system, inhibit a thorough understanding of the process. In this study, we propose a thermodynamic model in an isothermal open system to enable ion exchange without an imaginary volume expansion. We derive a fundamental equation and verify it using atomistic images obtained by Raman spectroscopy and nuclear magnetic resonance. This study paves the way for further atomistic design and development of strengthened glasses. [ABSTRACT FROM AUTHOR]

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 understanding of the nature of the strength and development of stronger glasses, we need a method directly connected to atomic-scale glass structures. Here, we propose a method based on the "stuffing" effect, where we can determine the residual stress non-contactively and non-destructively with a high spatial resolution using Boson, D1, D2, and A1 peaks in micro-Raman spectra. Finally, we show a plausible depth dependence of the residual stress. The strength of glass can be increased post-production by treatment with chemical processes, and such materials are used in everyday devices such as mobile phones. Here, the authors report a non-invasive method based on micro-Raman spectroscopy to analyse the compressive stress responsible for the increased strength of the treated glass. [ABSTRACT FROM AUTHOR]

Structural ordering in the glass phase during heating processes (i.e., crystallization) creates aggregate textures with diverse phases in ceramic materials. In this study, we focused on a glass-ceramic technique as a new approach for the formation of heterostructures enabling electronic interactions between different crystallized phases. In this study, we fabricated diversely phased glass-ceramics (DPGCs) from a binary Bi 2 O 3 – SiO 2 glass precursor and investigated the visible-light-responsible photocatalytic reaction. We found the co-precipitation of metastable Bi 2 SiO 5 and δ-Bi 2 O 3 phases in the heat-treated precursor, and the resulting DPGCs were confirmed to show remarkable photocatalytic activity under visible light irradiation, ascribed to the heterojunction between the Bi 2 SiO 5 and δ-Bi 2 O 3 phases. This study not only demonstrates the heterostructure using DPGCs but also has practical significance in contributing to the mass production of visible-light-responsive photocatalysts using simple heat treatment. [ABSTRACT FROM AUTHOR]

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 phenomenon is attributed to a photo-chemical modification of Ag-ion distribution in amorphous AgAsS2. [ABSTRACT FROM AUTHOR]

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 the oxide glass optical transparency due to light scattering. The dispersion of the MgO crystals increased the thermal conductivity of the original glass by ∼50% and the new glass still exhibited optical transparency. Such MgO-dispersed glass could be successfully used in thermal management applications requiring both transparency and formability. [ABSTRACT FROM AUTHOR]

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 compression layer by CO 2 laser scanning and provide its visualization by Raman mapping. We demonstrate cutting the scanned glass without shattering using a typical scribing wheel. Finally, we discuss the improvement in processability from the viewpoint of microscopic structures by means of thermal analysis and Raman spectroscopy. [ABSTRACT FROM AUTHOR]

[Display omitted] • We deposited La 5 Ca 9 Cu 24 O 41 on heated substrates via rf sputtering. • The substrate heating led to a columnar structure and the b -axis orientation. • The columnar structure can be explained by the usual columnar growth model. • The Cu–O bonds forming the ca plane can be dominant for the b -axis orientation. Spin-ladder cuprates such as La 5 Ca 9 Cu 24 O 41 are promising materials for advanced thermal management applications owing to their highly anisotropic and dynamically controllable thermal conductivity originating from spin ladders. Therefore, the orientation control of spin ladders is required in film fabrication methods that are extensively used in device engineering, such as sputtering. We found that La 5 Ca 9 Cu 24 O 41 films with a columnar structure and the face-on orientation of spin ladders are formed on heated SiO 2 (glass) and Si substrates via radio-frequency magnetron sputtering. The structural properties of the films were investigated, and the film formation mechanism was discussed. Our film fabrication method can pave the way for the development of new thermal management devices, such as active heat spreaders. [ABSTRACT FROM AUTHOR]

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 limited to that concerning theoretical perspectives and investigation of physical properties using large single crystals. In this study, we adopt glass-ceramics technique to synthesize these materials: We prepared melt-quenched multicomponent oxides including SrO and CuO, and checked its glass-forming ability and crystallization behaviors by heating. As a result, we have found that SrCuO2 and Sr14 Cu24 O41, known as the spinon thermal conductivity materials, are synthesized using SrO- CuO-- Li2 O-- Al2 O3-- Ga2 O3 system. This synthesis process for the system will provide practical application of the spinon thermal conductivity materials. [ABSTRACT FROM AUTHOR]

We prepared SrCuO 2 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 SrCuO 2 nanothick crystals belonging to tetragonal system, i.e., the layer-type SrCuO 2 . Raman-scattering spectra show that irradiation of high-power super-band-gap laser light onto the film gives rise to structure change into orthorhombic system, i.e., the chain type SrCuO 2 , which is known to exhibit high, anisotropic thermal conductivity due to spin interaction. A mechanism of the structure change is discussed in terms of photoexcitation and heating process. [ABSTRACT FROM AUTHOR]

Optical glass fibers can propagate light signals, while their control depends on nonlinear optical crystals. In this study, we fabricated nonlinear optical glass-ceramic (GC) fibers in which the polar fresnoite phase was crystallized based on perfect surface crystallization (PSC) in the SrO–TiO 2 –SiO 2 system. GC fibers free from voids were obtained from precursor glass fibers with a diameter of ∼100 μm by controlling PSC. The propagation loss of a GC fiber was evaluated to be ∼0.37 dB/cm, which is comparable to that of the LiNbO 3 single-crystal optical waveguide. [ABSTRACT FROM AUTHOR]

Abstract: 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 estimated from the impedance, is in agreement with a geometrical thickness measured by an atomic force microscope for chemically etched samples. Under the photodoping (with zero bias voltages), a photocurrent remains constant at ~5pA, and near the completion it increases to ~1nA, which is followed with a gradual decrease. By applying a bias voltage between the top (semi-transparent Al) and bottom (Ag) electrodes, we can change a photodoping rate by an order. This rate change is attributable to the modulation of an effective electric field in the doped layer, which induces the motion of Ag ions. [Copyright &y& Elsevier]

Abstract: 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 that stoichiometric GeO2–GeS2 glasses have a heterogeneous structure in the scale of 1–100nm. The optical gaps are nearly constant at 3.0–3.5eV for glasses with 0⩽ x ⩽80mol% and abruptly increase to ∼6eV in GeO2. This dependence suggests that the optical gap is governed by GeS2 clusters, which are isolated and/or percolated. Composition-deviated glasses appear as orange and brown, and these glasses seem to have more inhomogeneous structures. [Copyright &y& Elsevier]

Abstract: 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 show a disappearance of a crystalline peak, and the illuminated surfaces expand. These observations can be accounted for by assuming bond transformations from rutile-like to defective quartz-like structures and/or from small to large rings. These photo-induced changes in GeO2 are discussed in comparison with those in SiO2 and GeS2. [Copyright &y& Elsevier]

Abstract: Macroscopic and microscopic changes in sputtered GeO2 films induced by band-gap light from an ArF excimer laser have been studied. When irradiated at 1atm, the film thickness increases, surface-roughness increases, refractive-index decreases, hygroscopic enhancements, and Ge–O–Ge distance increases. Irradiations in vacuum make these changes smaller or undetectable. These photo-induced changes are discussed from phenomenological and structural viewpoints, and compared with characteristics in GeO2–SiO2 and GeS2 films. [Copyright &y& Elsevier]

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 this material as probe phosphor by thermoluminescence measurements. The evaluated sensitivity value of the zirconia was 10 %/K, which was higher than typical materials used in luminescent thermometers. Therefore, the prepared zirconia is a great candidate as a harmless and biocompatible sensing probe. [ABSTRACT FROM AUTHOR]

Abstract: 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 induced by photoelectronic excitation in the Mg–Sn–O film, electron injection into the metal oxide, which becomes negatively charged, and subsequent formation of metallic particles, which absorb and/or scatter visible light. [Copyright &y& Elsevier]

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 dynamically controlled by an external field. Here, we demonstrate the electric control of heat flow using a polycrystalline cuprate film and an ionic liquid. The results showed that a voltage application to the interface causes imperfectly recoverable decreases in both the thermal conductance of the film and the peak due to magnons in the Raman spectra. This result may be attributed to an increase in the hole density in the spin ladders. This report highlights that magnon thermal conduction has potential for the development of advanced thermal management applications. [ABSTRACT FROM AUTHOR]

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 produced optically stimulated luminescence, followed by afterglow, with the property of repeating 100 times or more. Furthermore, the basic principle of temperature measurement was demonstrated through afterglow decay curve measurements. The use of harmless ZrO2 as a sensing probe and NIR light, which is relatively permeable to living tissues, is expected to realize temperature measurements in the brain and may also facilitate optogenetic treatment. [ABSTRACT FROM AUTHOR]

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) phosphor is examined to validate its use as a sensing probe. In addition, assuming the measurement in deep-part of human body, we have applied the information gathered from our validation to observe OSL from the ZrO2 by irradiation with near-infrared laser through a bone sample. This study demonstrates an alternative medical application of phosphor, and introduces an elemental-technology for the temperature sensing. [ABSTRACT FROM AUTHOR]

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 exhibited the Pockels coefficients, i.e., r 13 ∼ 3.0 pm/V and r 33 ∼ 2.4 pm/V, and the coefficients exceeded the reported values of the PSC-GCs with Sr 2 TiSi 2 O 8 phase. The improvement of Pockels effect is attributed to the higher crystal-orientation, which is provided by the lower-temperature condition. [ABSTRACT FROM AUTHOR]

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 pronounced, visually observable bluish LLP that lasted for ~ 10 h at moderate temperature. Based on spectroscopic observation and electron spin resonance results, a possible origin of the LLP is discussed. [ABSTRACT FROM AUTHOR]

Optical modulation based on second-order optical nonlinearity is required to control a light-wave for telecommunication with optical-fiber network, and its 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 effective. In this study, a bulk-like GC material with a polar fresnoite-type Ba 2 TiGe 2 O 8 were successfully fabricated. The obtained GCs were formed by densely-aggregated structure of two phase, fresnoite-type (major phase) and tetragermanate (minor phase). The fresnoite-type Ba 2 TiGe 2 O 8 domains with submillimeter-sized were oriented with the polar c -axis perpendicular to sample plane. The GC sample exhibited the optical modulation driven by Pockels effect, and the Pockels coefficients could be quantitatively estimated, i.e., r 13 = 2.3 ± 0.1 pm/V and r 33 = 2.5 ± 0.1 pm/V. The experimental results demonstrate the potential of higher Pockels coefficients by microscopic structural studies, because of good controllability of the polar orientation and suppression of secondary phase. [ABSTRACT FROM AUTHOR]

Abstract Recently, we have developed the borosilicate glass, in which ZrO 2 phase is singly crystallizable, and has found an emissive monoclinic ZrO 2 dendrites in the resulting GCs. In order to promote the formation of monoclinic phase, we have examined the effect of substitution of alumina Al 2 O 3 for ZrO 2 in the precursor glass composition, i.e., 15Na 2 O–(15 − x)ZrO 2 – x Al 2 O 3 –30B 2 O 3 –40SiO 2. It was found that the substitution of small amount of Al 2 O 3 (x = 1) gave a positive effect, i.e., increase in the amount of monoclinic phase and decrease in the crystal size. Furthermore, the substitution improved the internal quantum-yield. On the other hand, the further substitution (x ≥ 2) provided the decrease in amount of the monoclinic phase. [ABSTRACT FROM AUTHOR]

We investigated the Pockels effect in polycrystalline materials consisting of highly oriented polar fresnoite-type Sr2TiSi2O8 fabricated using perfectly surface-crystallized glass-ceramics (PSCGCs). The chemical composition of the precursor glass was shown to significantly affect the crystallized texture, e.g., the crystal orientation and appearance of amorphous nanoparasites in the domains, resulting in variations in the Pockels constants. Single crystals exhibiting spontaneous polarization possessed large structural anisotropy, leading to a strong dependence of the nonlinearoptical properties on the direction of polarized light. This study suggests that variations in the Pockels constants (r13 and r33) and tuning of the r13/r33 ratio can be realized in PSC-GC materials. [ABSTRACT FROM AUTHOR]

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 succeeded in observing the photocatalytic activity of TiO 2 crystallized glass. Since glass-based material is suitable for industrial use, crystallized glass is expected to be a novel bulk photocatalyst with high productivity if we provide visible light response ability to TiO 2 crystallized glass. In this study, we tried the defect introduction to TiO 2 crystallized glass and investigated the photocatalytic activity under visible light irradiation. As a result, we have demonstrated water splitting by TiO 2 crystallized glass with Ti 3+ defect under visible light irradiation for the first time. [ABSTRACT FROM AUTHOR]

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 employed as the precursor, merits of glass material are fully utilized to fabricate the optical device component, in addition to that of functional crystalline material, leading us to provide an electro-optic device, which is introducible into glass-fiber network. [ABSTRACT FROM AUTHOR]