To advance a sustainable society, increasing attention has been directed toward the development of high-performance materials and environmentally responsible synthetic methodologies. Cation-disordered materials have attracted attention across various fields because of their exceptional performance. However, their synthesis requires high-temperature calcination or after-treatment of cation-ordered precursors, resulting in high energy consumption levels, extended processing times, and increased costs, which hinder commercialization. Recently, low-temperature solution-based reactions enabling the synthesis of cation-disordered structures via instantaneous crystallization using spray dryers have been reported; however, technical insights into these processes remain unclear due to very few reports compared with those for solid-state reactions. In this study, we demonstrate low-temperature one-pot synthesis (<40 °C) of cation-disordered Li3VO4, a high-performance anode material, from a solution reaction via a combination of a rotary evaporator and a vacuum dryer, which are standard laboratory apparatuses, under strictly controlled conditions. This cation-disordered Li3VO4 is identified as a kinetically stabilized metastable phase and undergoes a moisture-induced phase transition to the thermodynamically stable β-phase, which results in inferior performance. Moreover, it can be dissolved in water and reverted to its precursor ions, indicating its recyclability. This methodology, in which a kinetically stabilized crystal phase is synthesized via evaporation-driven crystallization, supports the development of innovative materials that simultaneously achieve green chemistry and high performance.

Holographic images reconstructed by ferroelectric-liquid-crystal (FLC) pixel arrays with a pixel pitch of 1 μm show asymmetric brightness across the viewing zone under oblique illumination, i.e., the image at one edge is darker than that at the opposite edge. Mathematical calculations based on FLC grating models clarified that the brightness asymmetry becomes more pronounced for smaller pixel pitches and originates from differences in optical path length due to larger diffraction angles, which increase the geometrical path length and change the polarization state at the FLC surface. These results provide important insight into the asymmetry and are useful for designing illumination for holographic displays.

We present a method to enhance the layered structure of surface-stabilized ferroelectric liquid crystals (SSFLCs) for low-voltage, high-speed operation in electronic holographic displays. By applying a combination of heating, slow cooling, and square-wave low-voltage (<1 V), we reduced the switching voltage and achieved sub-1 ms switching times, fulfilling the 360-720 Hz requirements for spatial light modulators (SLMs) in electronic holographic displays. The proposed method also suppressed zigzag defects, improving uniformity and light efficiency. This work advances high-resolution SSFLC-based SLMs for next-generation 3D holographic displays.

We reduced the electrode pitch to 0.7 pm and drove the ferroelectric liquid crystal (FLC) at a low voltage of 1 V to realize a spatial light modulator (SLM) with small pixels for a holographic display with a wide viewing zone angle. Even with an extremely small electrode pitch of 0.7 pm, the FLC could be driven at a low voltage of 1 V. We also evaluated the switching angle and response time of the FLC on the fine-pitch electrodes and found that the switching angle decreases and the response time increases when the electrode pitch is reduced. This work shows the possibility of applying the SLM using the FLC to a holographic display with a wide viewing zone angle.

We clarified that a ferroelectric liquid crystal (FLC) has high resolution display capability as small as 1 x 1 mu m pixel pitch using an FLC pixel array with a two-layer electrode, which has a 1 x 1-mu m-checkered apertured electrode and a plane electrode separated by an insulation layer. By applying +2 V to the apertured electrode and -10 V to the plane electrode in the two-layer electrode and 0 V to the transparent common electrode, a checkered pattern was clearly observed, which indicates the successful individual pixel driving with a pixel pitch of 1 x 1 mu m. When fabricating 1 x 2-mu m-pitch rectangular FLC pixels, we elucidated that the liquid crystal alignment direction should be along the shorter side of the pixels to avoid asymmetric transmittance distribution in each pixel. Moreover, we successfully reconstructed a 3D holographic image using 10 x 10 k FLC pixel array with a pitch of 1 x 1 mu m driven by the two-layer electrode with hologram-patterned apertures. We showed that FLC is a strong candidate material for realizing spatial light modulator with extremely small pixel pitches, which is essential for holographic displays with wide-viewing-zone angles. We clarified that a ferroelectric liquid crystal (FLC) has high resolution display capability as small as 1 x 1 mu m pixel pitch using a two-layer electrode and demonstrated a three-dimensional holographic static image with the FLC and two-layer electrode.image

We have studied high-speed optical phased arrays (OPAs) using electro-optic (EO) polymers for various applications, including range imaging, three-dimensional shape measurement, spatial light communication, and image display. The suppression of the stray light caused by radiation loss in curved waveguides and coupling loss in optical splitters is very important in OPAs using EO polymer. Stray light causes degradation, for example, in the image quality on a display or the signal-to-noise ratio on an optical sensor. In this study, we investigate optical loss reduction by optimizing the design of a curved waveguide and an optical splitter to suppress stray light and improve the optical beam quality from OPAs. We perform numerical simulations and an experimental evaluation of the designed OPAs and confirm the effectiveness of the optimal design for stray light suppression.

Aluminum solid electrolytic capacitors using conductive polymer cathodes are promising passive components with high capacitance, low equivalent series resistance (ESR) and high thermal stability for applications in advanced power electronics systems. However, the working voltage of the aluminum solid capacitors is limited and does not meet the requirements of the power electronic systems. In this study, two approaches are introduced to increase the withstand voltage of the aluminum solid capacitors: introducing a highly resistive interface layer between a dielectric alumina layer and a conductive polymer layer and the development of novel modified PEDOT:PSS polymers. When a crystalline g’-alumina dielectric layer covered with a porous hydrated alumina layer was coated with a PEDOT:PSS conductive polymer, the breakdown voltage was ~500 V for the dielectric alumina film formed at 700 V. The dielectric breakdown occurred at voltages considerably lower than the anodizing voltage. However, the introduction of the simple hot water treatment after anodizing (post-hydration treatment) increased the breakdown voltage markedly, exceeding the anodizing voltage of 700 V.1 Cross-sectional STEM observation of the cross-section of the post-hydration treated specimen disclosed the formation of a nanovoids-dispersed layer between the dielectric layer and the hydrated alumina layer. The nanovoids-dispersed layer contained a reduced amount of polymer, so this layer is likely to be more resistive. Re-anodizing to convert the nanovoids-dispersed layer to a dielectric layer reduced the breakdown voltage to ~500 V. Thus, it is confirmed that the formation of such nanovoids-dispersed layer with high resistivity plays an important role in enhancing the breakdown voltage of the aluminum solid capacitors. Alkyl group-modified PEDOT:PSS conductive polymers were synthesized to control the crystallinity and conductivity. The crystallinity and conductivity of the PEDOT:PSS were successfully reduced by introducing the alkyl group, and we could confirm that the breakdown voltage of the capacitors was highly enhanced by using ethyl-PEDOT:PSS instead of commercial PEDOT:PSS. D. Quintero, H. Matsuya, M. Iwai, S. Kitano, K. Fushimi, H. Habazaki, ACS Appl. Mater. Interfaces, 16 (2024) 1737-1748. This study was supported in part by the MEXT-Program for Creation of Innovative Core Technology for Power Electronics (INNOPEL), Grant Number JPJ009777.

This study proposes a method for enlarging the viewing zone of holographic displays using the slanted arrangement of pixels on a spatial light modulator (SLM). The pixel arrangement equivalently reduces the horizontal pixel pitch, which enlarges the horizontal viewing zone of displays. Computer-generated holograms (CGHs) were calculated using an asymmetric band-limit filter corresponding to the asymmetric bandwidth of the SLM with slanted pixels. The proposed methods were evaluated through an optical reconstruction experiment using static holograms with a pixel size of 1×1µm, fabricated via electron-beam lithography. The enlarged horizontal viewing zone angle was found to be 41.6°.

This study explores the potential of titanium ion (Ti4+) substitution in gamma-Li3VO4 (gamma-LVO) as an anode material for high-energy supercapacitors. A series of Li3+xV1-xTixO4 (x = 0, 0.05, 0.10, 0.15, and 0.20) are systematically synthesized to vary the Ti-substitution ratio within LVO, and their crystal phases were analyzed using X-ray diffraction (XRD). Additionally, the reactivity of Ti during charge-discharge cycles is assessed by monitoring in situ X-ray absorption fine structure (XAFS) spectral changes. Quenching methods and XRD measurements quantitatively reveal that substituting 20 atom % of V5+ with Ti4+ achieves a single-phase gamma-LVO, distinct from the nonsubstituted LVO (beta-phase LVO). The Ti-substituted gamma-phase LVO electrode displays a supercapacitor-like voltage curve and exceptional high-power performance during charge-discharge tests, benefiting from its high ionic conductivity stemming from the LISICON (Lithium Super Ionic CONductor) crystal structure. Furthermore, the Ti-substituted gamma-phase LVO electrode exhibits an impressive rate capability, retaining 50% of its capacity at a very high current density of 2 A g(-1) (10C-rate), while the nonsubstituted LVO retained only 13% under the same conditions. GITT analysis confirms a 100-fold higher Li+ diffusion coefficient for the Ti-substituted gamma-phase LVO electrode. A novel approach is employed to examine the kinetic effects of Ti substitution on gamma-phase stabilization: halting or quenching the gamma -> beta phase transition during cooling using liquid nitrogen, coupled with XRD measurements, facilitates a quantitative evaluation of the phase transition rate. The primary goal of this study is to conduct a comprehensive assessment of the crystal structure and its stability by taking advantage of the excellent traceability of the Ti element through X-ray measurements to achieve this aim.

Proceedings of the International Display Workshops Volume 30 (IDW '23),Holographic Image Reconstruction Using a Magneto-Optical Spatial Light Modulator with Its Pixel Pitch of 1 μm and its Layout of 10k × 5k

We have proposed a magneto‐optical spatial light modulator (SLM) for holography application which magnetization is switched by spin polarized current injection. It has potential to reduce the pixel size less than one micron for large viewing zone angle over 30 degrees, which no commercial SLMs have achieved.

We proposed a technique for the computer-based reconstruction of computer-generated holograms and evaluation of the reconstructed 3D image quality. The proposed method mimics how the eye's lens works, thus allowing for viewing position and eye focus adjustments. The angular resolution of the eye was used to output reconstructed images with the requisite resolution, and a reference object was used to normalize the images. Such data processing enables the numerical analysis of image quality. By comparing the reconstructed images with the original image with incoherent illumination, the image quality was quantitatively evaluated.

We have developed a magneto-optical spatial light modulator (MO-SLM) with a 10 k × 5 k pixel layout and with a pixel pitch horizontally of 1 µm and vertically of 4 µm. An MO-SLM device pixel has a magnetic nanowire made of Gd-Fe magneto-optical material whose magnetization was reversed by current-induced magnetic domain wall motion. We successfully demonstrated the reconstruction of holographic images, showing large viewing zone angles as wide as 30 degrees and visualizing different depths of the objects. These characteristics are unique to holographic images, providing physiological depth cues which may play a vital role in three-dimensional (3D) perception.

Conversion efficiency of a dye-sensitized solar cell (DSC) using poly(3,4-ethylenedioxythiophene) (PEDOT)-coated transparent conducting substrate as a counter electrode was shown to be 7.88 %, which is slightly higher compared to a DSC using classical platinum sputtered counter electrode (7.65 %). From electrochemical impedance analysis, the PEDOT based cell was found to show lower charge-transfer resistance assigned to the I−/I3− redox reaction as a mediator on the counter electrode compared to the platinum based cell. More quantitatively, electron transfer rate constant (k0) for the I−/I3− redox reaction on the counter electrode was remarkably estimated by voltammetric kinetic analysis. The k0 obtained for the PEDOT electrode (3.47 × 10−3 cm s−1) was larger than that for the platinum electrode (2.76 × 10−3 cm s−1) of the approximately same electrode thickness and surface roughness. This research revealed the higher conversion efficiency of the PEDOT based cell is essentially attributed to the faster mediator reaction (reduction of I3−) on the counter electrode in its cell.

We assessed the image quality in holographic near-eye displays by faithfully simulating coherent image formation on the retinal plane and comparing the simulated results with those of incoherent imaging.

We compare the diffraction characteristics of ferroelectric (FLC) and nematic liquid crystal (NLC) devices with one-dimensional stripe patterns of 1-10 mu m pixel pitches. The polarizing micrographs show pixel boundaries of black/white pixels blur as the pixel pitch becomes smaller. The blur of NLC is more remarkable than that of FLC. The first-order diffraction efficiency of NLC remains constant for the pixel pitch of 4-10 mu m and sharply decreases for the pixel pitch of < 2 mu m. By contrast, the FLC efficiency decreases with the pixel pitch decrease from 10 to 4 mu m and remains constant for the pixel pitch of < 3 mu m. The FLC efficiency (5.5%) is four times larger than that of NLC (1.4%) with a 1 mu m pixel pitch. The Fourier transform calculation shows the efficiency degradation of FLC is caused by the blur at the pixel boundary, whereas that of NLC caused by the blur and contrast deterioration.