In this study, hafnium aluminum oxide (Hf_1−xAl_xO_y) alloy thin films were successfully deposited using a fine-channel, single-source mist chemical vapor deposition (mist-CVD) system. The precursor solution was prepared by co-dissolving hafnium (Hf) and aluminum (Al) precursors in methanol. Hf_1−xAl_xO_y films with different Al compositions in the range 0 ≤ x ≤ 1 were prepared and then characterized using grazing incidence X-ray diffraction (GIXRD), spectroscopic ellipsometry, and X-ray reflectivity measurements. GIXRD analysis confirmed that the incorporation of Al in HfO₂ led to the formation of amorphous alloy films (x > 0.38). Increasing the Al content in the film decreased the refractive index and mass density while widening the bandgap, reflecting the compositional change from HfO₂ to Al₂O₃. Moreover, the properties of the mist-CVD-derived Hf_1−xAl_xO_y films were comparable to those reported in the literature, which were prepared via conventional vacuum-based atomic layer deposition. These findings suggest that mist-CVD is a promising solution-processed and non-vacuum technique for depositing high-quality Hf_1−xAl_xO_y alloy films.

Many oxides with high dissociation energies also have high melting points; therefore, concurrently achieving a low glass transition temperature, high thermal stability, high optical transparency, and high mechanical strength is challenging. In this study, aluminoborate glasses with high hardnesses and Young’s moduli were prepared using the conventional melt-quenching method. The glasses exhibited packing densities greater than 0.59 and Poisson’s ratios of approximately 0.29, which are indicative of a densely packed network structure. The fabricated glasses had low glass transition temperatures (<760 °C) and high Young’s moduli (>120 GPa), as well as sufficient thermal stability for fiber drawing and transparency in the visible region. Developing oxide glasses with physical properties that are difficult to achieve is expected to expand the frontiers of material applications and drive further advancements in glass science.

Containerless processing was used to access and study supercooled liquids and glasses that cannot be made using conventional melting approaches. In-situ measurements of melt atomic structure and density provided insight into how the glass forms. Experiments included making measurements in microgravity where buoyancy driven convection and sedimentation are suppressed. Here we examine the structure and properties of rare earth-aluminate composition liquids and some glasses made from them. The structures show a fundamentally different network behavior from the classical Zachariasen model. The network comprises four and about 40 % five coordinated aluminum ions that share corners or edges and often form triply bonded species with an oxygen ion. The concept of Kⁿ is used to evaluate the glass forming behavior in terms of network connectivity and bonding. The temperature dependence of density of the liquid is reported and discussed in the context of processing molten materials in reduced gravity where bubbles can be trapped in the liquid due to lack of buoyancy. The interior structure in samples was investigated using X-ray tomography to investigate how bubbles can cluster inside a liquid drop.

Sodium aluminate solution has been used in various industrial applications, including refractories, building materials, and catalysts. However, since it has been designated as a deleterious substance under the Poisonous and Deleterious Substances Control Act in Japan, restrictions for handling this material are increasing, necessitating the development of an alternative alkaline aluminum solution. This study aimed to develop an alkaline aluminum solution as a replacement for sodium aluminate. For this purpose, tetraethylammonium hydroxide (TEAH) was selected as the base. The stability of the solution obtained from the reaction between TEAH and the aluminum hydroxide gels prepared from hydrolyzed polyaluminum chloride (PAC) or that of the solution obtained from direct reaction of TEAH and PACs was examined. From the ²⁷Al NMR, it was confirmed that both 4- and 6-coordinated aluminum species co-existed in the solution prepared from aluminum hydroxide gels, and that boehmite derived from 6-coordinated aluminum species precipitated upon storage. On the other hand, alkaline aluminum solutions without precipitation during storage at 50 °C for 2 weeks were obtained by direct reaction of TEAH and PACs with a basicity below 40 %. In these solutions, the absence of 6-coordinate aluminum species, which form precipitates during storage, indicates a stable condition. These solutions are expected to serve as a new alkaline aluminum solution for industrial applications in the future.

We fabricated piezoelectric multilayer ceramics using (K,Na)NbO₃ (KNN)-based ceramics with Ni internal electrodes and investigated the effects of sintering temperature (1020–1040 °C) on their electrical properties and reliability. Overall, sintering at 1020 °C yielded the highest piezoelectric strain response (406 pm/V) and the highest room-temperature volume resistivity (4 × 10¹⁰ Ω·m), although these values did not significantly differ from samples prepared at 1030 and 1040 °C. However, in time-dependent insulation resistance measurements at 150 °C and 5 kV/mm, the degradation was significantly accelerated as the sintering temperature increased, thereby shortening the operational lifetime from 12 h (sintered at 1020 °C) to 6 h (sintered at 1040 °C). Microstructural analysis confirmed that a K-rich secondary phase formed near the grain boundaries, and the K concentration in this region increased with sintering temperature. This secondary phase may be a cause of the rapid insulation degradation, particularly for KNN-based ceramics with Ni internal electrodes sintered at higher temperatures.

Structural colors derived from colloidal crystals are gaining attention as new color materials that are non-toxic and minimize environmental pollution. Vivid structural colors were formed by coating glass and ceramics with a colloidal crystal (opal) thin film composed of silica particles. This paper focuses on reporting this thin film formation process. A milky-white suspension of silica particles (particle size 290 nm) precisely arranged on the substrate surface exhibited vivid red structural color after drying. The dip coating is not limited to flat substrates like glazed ceramics or glass; it is versatile and can be applied to curved surfaces, uneven surfaces, and even rough, unglazed ceramic surfaces. Optical evaluation utilized reflectance spectra. By employing silica opal films with varying particle sizes, diverse colors spanning the entire visible spectrum from blue to red were achieved. Furthermore, through heat treatment and modification to create a hydrophobic surface, stable structural color emission was enabled, preventing loss of color due to abrasion or wetting.

Inorganic–organic hybrid gas barrier films were prepared using atmospheric-pressure plasma-enhanced chemical vapor deposition (AP-PECVD) with tetramethoxysilane (TMOS) and methyltrimethoxysilane (MeTMOS). The effect of MeTMOS content on the gas barrier properties [oxygen permeability coefficient and water vapor transmission rate (WVTR)] of the films was investigated. The oxygen permeability coefficient of the hybrid layer was low, approximately one-fourth that of polyvinylidene chloride (PVDC). The WVTR of the hybrid layer (normalized to 25 µm thickness) was of the same order as that of PVDC. The light transmittance of the hybrid gas barrier film coated on polyimide (PI) was 75.7 % at 600 nm, and the pencil hardness (750 g load) was 5B. In the flexibility tests, where the film was bent ten times around a 2 mm diameter stainless steel rod, no cracks were observed on the surface of the film. The hybrid gas barrier films exhibited excellent oxygen and water vapor barrier properties, in addition to transparency, hardness, and flexibility.