The effects of P₂O₅ substitution on the coordination structure of a Bi³⁺ in Bi₂O₃–B₂O₃ glasses were examined by applying ¹¹B and ³¹P MAS-NMR spectroscopy. Observation of the wide optical bandgap after the substitution revealed a substantial difference in the solvation shell structure between the P₂O₅ substituted and the P₂O₅-free Bi₂O₃-containing glasses, i.e., the P₂O₅ substitution replaced by the B₂O₃ is effective for forming the solvation shell, which leads to weak ligand field around a Bi³⁺. We report the optical properties of the Bi₂O₃–P₂O₅–B₂O₃ glass providing a wide optical bandgap (∼3.6 eV) and high refractive index (∼2.0).

Iron phosphate (IP) glasses containing both 10 mol % BaO and 6–18 mol % MoO₃ consist mainly of Q¹ PO₄ structural units and small amounts of Q⁰ and Q² species, where n in Qⁿ is the number of bridging oxygen atoms per PO₄ tetrahedron. The PO₄ units are connected to Mo⁵⁺O₆ distorted octahedra with Mo⁵⁺–O–P bonds and to Fe-related polyhedra with Fe–O–P bonds to minimize the formation of P–O–P bonds. The IP glasses that contained both Ba and Mo (BaMo-IP) exhibited superior water durability than those containing only Mo (Mo-IP). After immersion tests in ultrapure water at 120 °C for 72 h, the weight loss per specific area in BaMo-IP glasses showed values that were one-fifth to one-tenth smaller than those in Mo-IP glasses. This result was related to a reaction layer that formed at the sample surface during the immersion process. Microstructural observations revealed that this layer was ∼50 nm in thickness and composed of six-line ferrihydrite and phosphorus-containing noncrystalline phases, and it exhibited a homogeneous nanogranular structure. The reaction layer served to protect against water corrosion.

Although silica-substituted octacalcium phosphate (OCP–silica) blocks have demonstrated outstanding biocompatibility and bone-regeneration capacity, their mechanical strength is insufficient for further applications. Therefore, in this study, we introduce a novel process for fabricating OCP–silica based on the cement-setting reactions of CaCO₃, H₃PO₄, and Na₂SiO₃. Despite having the same basic composition as the acidic calcium phosphate powder used in the initial components, the mechanical strength of the fabricated OCP–silica blocks [diametral tensile strength (DTS) of ∼1.0 MPa] was approximately threefold greater than that of the legacy blocks (DTS of ∼0.3 MPa). The fabricated OCP–silica blocks exhibited a fine structure consisting of closely interlocked, well-developed, plate-like crystals. The high mechanical strength of the fabricated blocks is attributed to the close interlocking of the OCP crystals. The fabricated OCP–silica (CaCO₃) blocks exhibited sufficient mechanical strength to be used as a bone substitute; thus, the fabrication process reported herein provides a valuable tool for advancing clinical applications.

A standard chrysotile sample was combined with erythrosine in an aqueous solution. Digital microscopy and energy-dispersive X-ray spectroscopy-scanning transmission electron microscopy (EDS-STEM) observations revealed that erythrosine was thinly and uniformly bonded to the surface of the fibrous chrysotile, forming a reddish-purple chrysotile/erythrosine composite. The amount of erythrosine adsorbed on the chrysotile was evaluated using EDS-STEM, thermogravimetry-differential thermal analysis (TG–DTA), N₂ adsorption–desorption isotherms, and erythrosine-adsorption isotherm. Zeta-potential measurements showed that chrysotile had a positive surface potential; however, the chrysotile/erythrosine composite had a negative surface potential. In the aqueous solution, chrysotile and erythrosine were bonded through electrostatic interactions to form a composite. This study improves the reliability of the proposed simple and inexpensive asbestos-detection method to enable its practical application.