Murataite is a rare oxide mineral composed of Ti, Zn, alkali metals, alkaline earth metals, and rare earth elements. Murataite belongs to the cubic crystal system and has a crystal structure corresponding to the 3 × 3 × 3 (M3) superstructure of the fluorite structure. Synthetic murataite M3, which has a similar crystal structure of natural murataite-(Y) but with different compositions, and its synthetic polymorphs (strictly speaking, “polysomes”) of M5 and M8 are being applied to Synroc as host materials for long-term storage of radioactive actinoids. They are also expected to be used as electroceramics recalled from their fluorite-related crystal structures. This review provides a detailed explanation of the historical background of murataites researches, the crystal structure including polysomes, the processing and microstructure, and the potential applications as “rediscovered” ceramic materials.

Titanite-type oxides, ABMO₅, have been recently recognized as a novel vein of antiferroelectric (AFE) materials due to their unique crystal structure including an antiparallel arrangement of polar chains. This study presents the results of synthesis, structure analysis, and dielectric measurement of titanite-type solid solutions (Ca,Pb)TiGeO₅. With the Pb composition increasing, structural symmetry at room temperature changes from monoclinic to triclinic. We identified the crystal structure of PbTiGeO₅ by Rietveld refinement similar to that of triclinic titanite-type CaZrGeO₅. In addition, the AFE phase transition temperature is decreased by Pb substitution. These indicate the competition between triclinic and AFE distortions, in other words, lone-pair electrons on Pb²⁺ ions and the second-order Jahn–Teller effect on the Ti⁴⁺ ions.

In crystalline materials composed of multiple elements, such as alloys and solid solutions, degrees of freedom for atomic or ionic arrangements arise, making the determination of reasonable atom/ion configurations an important aspect of simulations. However, even in relatively small simulation cells, the number of possible arrangements is vast, rendering exhaustive evaluation infeasible. Although methodologies such as Monte Carlo and special quasi-random structures method have been proposed, genetic algorithm (GA) optimization is particularly useful for identifying stable arrangements, as it is applicable to bulk systems, surfaces, and interfaces. In this study, we improve the search method by combining GA with machine learning (ML), which we refer to as the GA and ML regression analysis (GAML). Specifically, this approach uses ML to screen and evaluate some of the structures generated by a GA, thereby reducing the computational demand of material simulations. This study provides an overview of the GAML, its computational methods, and optimization examples, demonstrating that the GAML achieves optimized structure more efficiently than the conventional GA. Integrating ML into GA significantly enhances the efficiency of optimizing atomic and ionic arrangements in crystalline solids. By achieving stable structures in fewer generations compared with traditional methods, the GAML offers a powerful tool for addressing complex systems with numerous possible configurations, with broad implications for accelerating materials discovery and design, particularly in fields requiring computationally efficient optimization of large and intricate systems.

Thin films of all-proportional PZT system, i.e., Pb(Zr_yTi_1.00−y)O₃ with y = 0–1.00, were deposited by hydrothermal deposition with a low reaction temperature of 150 °C. The PZT films were grown epitaxially on the surface of (100)SrTiO₃:La substrates via a microwave-assisted hydrothermal reaction using various input ratios of precursor chemicals x = [ZrOCl₂]/([ZrOCl₂] + [TiO₂]), which included more Zr ions (or less Ti ions) with a higher y value than that of the input ratio x. Dielectric and ferroelectric parameters for the resulting films, i.e., the relative dielectric constant (ε_r) and remanent polarization (P_r), exhibited maxima at the certain Zr/Ti ratio y = ∼0.60 though these parameters were relatively lower than those of the conventional films.

A multicomponent complex oxide, (W_0.41Mo_0.32V_0.19Ta_0.08)₅O₁₄, with a Mo₅O₁₄-type crystal structure and needle-like particles has been newly observed by scanning transmission electron microscopy (STEM), which confirmed that the four cations were homogeneously distributed in each particle. Each cation of this complex oxide seems to have a certain solid solution range for each valence. In this study, complex oxides with the same type of crystal structure could not be confirmed in a quaternary system or lower-order systems, namely, W–Mo–O, W–V–O and W–Mo–V–O. It is considered that the complex oxide was stabilized by simultaneously adding vanadium and tantalum. In addition, it was shown for the first time that this material has a Mo₅O₁₄-type structure with stable Li-ion battery characteristics. The initial discharge capacity was 161 mAh g⁻¹ (880 mAh cm⁻³) in the range of 1.55–3 V. The capacity was nearly constant and stable above 80 % even after 100 charge/discharge cycles.

P₂O₅ is an efficacious nucleating agent for promoting the crystallization of lithium disilicate glass, with numerous studies attributing its effectiveness to the formation of Li₃PO₄ crystals, which serve as heterogeneous nucleation sites for Li₂Si₂O₅ precipitation. However, recent studies have not consistently observed Li₃PO₄ precipitation. To address this controversy, this study utilizes Li₃PO₄ as a nucleating agent to determine whether Li₃PO₄ crystallites induce the precipitation of Li₂Si₂O₅. Additionally, Na₃PO₄, an analogue of Li₃PO₄, is employed to evaluate its potential to promote nucleation, while P₂O₅ serves as a comparative reference under identical conditions. Upon heating, all three agents fully melt in the glass. Subsequent heat treatment results in the precipitation of Li₂SiO₃ crystals, followed by Li₂Si₂O₅ crystals. It remains unclear whether these phosphates precipitate prior to the Li₂SiO₃ crystals. Although all agents exhibit comparable effects, the Li₂Si₂O₅ grain size in the Na₃PO₄ group is finer, leading to decreased strength and increased transparency in the samples. This may be due to the mixed alkali effect, where Na⁺ ions inhibit the growth of Li₂Si₂O₅ crystals. Notably, the initially precipitated Li₂SiO₃ crystals exhibit a higher Li content than the original glass, indicating that the nucleating agents alter the local glass composition to resemble that of the Li₂SiO₃ crystals, thereby facilitating crystallization. Subsequently, Li₂SiO₃ crystals decompose to form Li₂Si₂O₅ crystals, resulting in a redistribution of Li⁺ ions from localized enrichment back to a uniform distribution consistent with the original glass.

Most of the previous photocatalytic carbon dioxide (CO₂) reduction reactions proceeded in water using protons as a mediator. In contrast to conventional CO₂ reduction reactions in water, dry reforming of methane (DRM) reaction is attractive because it is uphill and can directly convert gaseous CO₂ with methane (two major greenhouse gasses) into valuable syngas (CH₄ + CO₂ → 2CO + 2H₂). Previous researches on DRM were mainly studied in the field of thermal catalysis, and it requires high operating temperature and causes deactivation by carbon precipitation so-called coking. The present paper reports an efficient photocatalytic DRM (Photo-DRM) using metal oxide-based semiconductors, such as rhodium loaded strontium titanate (Rh/SrTiO₃). The developed photocatalysts can drive DRM reaction over 50 % H₂ production yield under light irradiation even at low-temperature conditions for long-term. Generated amounts of CO and H₂ are twice as those of CH₄ and CO₂ consumption, suggesting the stoichiometric DRM reaction without any side reactions like coking. The mechanism of Photo-DRM is comprehensively studied by various analyses, including surface temperature measurement, action spectrum, electron spin resonance, isotope trace experiment, and gas-phase photoelectrochemical studies. Based on these analyses, photogenerated electron–hole pairs are the dominant active species for CO₂ reduction and CH₄ oxidation rather than the photo-thermal effect. Interestingly, the lattice oxygen ions (O²⁻) play an important role in Photo-DRM, where O²⁻ ions act as a mediator to link CH₄ oxidation and CO₂ reduction for producing H₂ and CO equally. By optimizing the conductivity of O²⁻ ions and band structure in semiconductors like CeO₂ and TaON, the Photo-DRM activities are greatly improved. The present mechanism using O²⁻ ions is different from the reported conventional photocatalysts, which use protons as a mediator. The concept of this study is not limited to the DRM reaction but is applicable to various other gas-phase reactions.

The thermoelectric properties of BiBO₃-added Bi₂Sr₂Co₂O_y ceramics have been investigated. Bi₂Sr₂Co₂O_y + x wt % BiBO₃ materials (x = 0, 0.16, 0.50, and 0.80) were prepared by the sol–gel method. The values of power factor (PF) and figure of merit (ZT) were evaluated using electrical resistivity (ρ), Seebeck coefficient (S) and thermal conductivity (k) measurements. The Bi₂Sr₂Co₂O_y + 0.16 wt % BiBO₃ sample has the lowest ρ among all studied materials. The S rises with a rising temperature above 400 K, indicating p-type conductivity for each sample. The value of S for the reference (pristine) Bi₂Sr₂Co₂O_y at 973 K is approximately 3–10 % higher than the BiBO₃-added compositions. Reference and 0.16 wt % BiBO₃-added samples exhibit higher PF values than those with higher BiBO₃ content (x = 0.50 and 0.80). Adding bismuth borate (x > 0.16) leads to a 1.6-fold decrease in the thermal conductivity of the Bi₂Sr₂Co₂O_y system at 573 K. The decrease of ρ (x = 0.16) and k (for all BiBO₃-added compositions) resulted in a 39 % improvement in the ZT value.

Silicon-based ceramic cores with aluminum silicate particles and fibers as mineralizers were prepared separately using the injection molding method. A comprehensive property evaluation model was proposed based on the physical property parameters of the ceramic cores, which were optimized using weight coefficients. A prediction model based on a backpropagation neural network was constructed to predict the effects of aluminum silicate fibers and particles as mineralizers on the properties of ceramic cores, and a properties optimization study on single materials were conducted. Additionally, a blending model was established to achieve cross-material properties predictions. The results indicate that the optimization predictions for single materials were more precise than those obtained through traditional experimental methods. The cross-material blending model identified an abnormal increase in the mean squared error at an addition amount of 1 wt.% aluminum silicate fibers, suggesting the presence of complex material behavior at this point. The full combination prediction results demonstrate that the neural network model performs well overall in predicting cross-material properties. The results of cross-material prediction show that the prediction results are in good agreement with the experimental measurement results, which indicate that the cross-material property parameter mapping and prediction of the neural network has good accuracy.

In thin-film actuators with PbZr_1−xTi_xO₃ (PZT)/SrRuO₃ (SRO)/Pt layered structures, the SRO buffer layer shows favorable effects such as improved electrical properties and reduced oxygen vacancies in the PZT film. However, when the PZT composition becomes near the morphotropic phase boundary for enhanced piezoelectric properties, the lattice misfit of approximately 3 % should be formed at the PZT/SRO interface. Consequently, a mechanism to relax this lattice misfit should be required. Here, we investigated the lattice misfit relaxation mechanism using (Scanning) Transmission Electron Microscopy [(S)TEM]. We found that the lattice misfit was relaxed not only by the edge-type misfit dislocations at the interface but also by the twins in the SRO buffer layer. The twins in the SRO film form prior to the PZT film deposition, possibly due to the surface condition of the Pt substrate. These findings suggest that the Pt surface condition may affect the structure and properties of PZT/SRO/Pt.

The purpose of the present study is to reveal functions of organic additives utilized in tape casting, a key technique for ceramic manufacturing. Interaction forces between alumina surfaces were measured using colloid probe atomic force microscopy (AFM) in dilute aqueous solutions containing both or one of polyvinyl alcohol (PVA) and glycerol. PVA and glycerol are typical additives for tape casting and are used as a binder and a plasticizer, respectively. In the PVA solution, repulsive forces due to steric hindrance were observed at separation distance about 10 nm. The glycerol solution exhibited a combination of attractive and repulsive forces, with a strong attraction at around 20 nm, attributed to the depletion effect caused by striking hydration ability of glycerol. The mixed solution of PVA and glycerol showed an increased repulsion distance of approximately 30 nm, suggesting that glycerol interacts with PVA molecules, altering their molecular conformation and expanding their gyration radius. The results indicate that addition of glycerol not only imparts mechanical flexibility to the green sheets but also stabilizes the alumina slurry. The empirically selected and optimized organic additives could fulfill multiple functions to improve the ceramic forming processes. As is presented in the study, the AFM colloid probe measurements would contribute to the understanding of how organic additives work and the development of more sophisticated ceramic processing.

Wollastonite is a calcium silicate (CaSiO₃) which has been widely studied as a ceramic raw material with its mechanical, insulative and bioactive properties. Since wollastonite undergoes crystal phase transition from β-CaSiO₃ to α-CaSiO₃, it is important to investigate the relationship between phase transition and material properties of wollastonite. In this study, Mg-doped wollastonite (β-Ca_1−xMg_xSiO₃) was synthesized, and quantitative phase analysis was conducted to reveal the effect of Mg on β-α phase transformation. As a result, when the phase transformation occurs at 1250 and 1300 °C, Mg dissolve in β-CaSiO₃ up to the solid solubility limits, forming β-Ca_0.94Mg_0.06SiO₃ and β-Ca_0.90Mg_0.10SiO₃, respectively. Additionally, since Mg hardly dissolves in α-CaSiO₃, the diffusion of Mg outward from β-CaSiO₃ crystal lattices slows down the rate of β-α phase transformation.

First-principles and molecular dynamics simulations are used to understand the stability and defect state of vanadium ions at BaTiO₃ grain boundaries. Qualitative analysis is performed based on two approaches to approximate polycrystalline grain boundaries. First, stable grain boundaries are modeled to evaluate the defect formation energies of grain boundary sites and bulk sites. Second, amorphous BaTiO₃ is used to analyze the relationship between defect structure and stability of vanadium. The electronic states of vanadium atoms in the amorphous state are statistically analyzed to understand the effect of complex structures such as grain boundaries. These results suggest that vanadium acts as a donor at grain boundaries.

The mechanical sensing technology based on mechanoluminescence (ML) shows several advantages such as remote response, stress distribution visualization and self-powering emission, which is expected to bring a breakthrough in the field of mechanical sensing. However, slow response and poor thermal stability are two major challenges in the ML-based sensing technology. In this work, an all-inorganic ML material β-SiAlON@glass was prepared by combining β-SiAlON (Si_6−zAl_zO_zN_8−z:Eu²⁺) phosphors with a low-melting-point glass. The β-SiAlON@glass showed the shortest ML lifetime of 9.8 µs reported so far, which was mainly due to the d-f electronic transition of Eu²⁺, very little persistent luminescence, and the high elastic modulus of the glass matrix. The β-SiAlON@glass exhibited excellent thermal stability with ML lifetime and peak intensity unchanged at temperatures up to 400 K. We revealed that the self-recoverable ML in the β-SiAlON@glass was primarily attributed to the triboelectric effect. Finally, we applied the β-SiAlON@glass to fabricate a ML sensor with a response time of 29 µs, which could clearly detect high-frequency ultrasonic waves at 25 kHz. The above results cannot only help us to further understand the mechanism in ML materials, but also provide an useful guidance for the development of high-performance ML sensors.

Bone fillers are used for bone defects caused by injury or disease. One type of such a bone replacement material is a bone cement that hardens by mixing calcium phosphates powder in a physiological environment. We have prepared gelatinized starch-containing bone pastes that harden by forming hydroxyapatite [HAp; Ca₁₀(PO₄)₆(OH)₂] while providing excellent handling property by mixing the powder and a gelatinized wheat starch. In this study, a starch-containing monetite-type bone paste was prepared by kneading bioabsorbable and biocompatible anhydrous calcium hydrogen phosphate (DCPA; CaHPO₄) powder with the gelatinized starch, and its properties were compared with those of the starch-containing HAp-type paste. The operability of the monetite-type paste samples was poor than that of HAp-type paste. In terms of crystalline phase, the monetite-type paste showed slightly different peak patterns attributed to DCPA before and after hardening, suggesting dissolution and reprecipitation of DCPA during soaking to set, while the HAp-type paste formed mainly HAp with trace amount of residual tetracalcium phosphate. Initial setting time of the monetite-type paste was longer than that of HAp-type one. Compressive strength exceeded 40 MPa for both of the sample types. In vitro bioabsorbability of the monetite-type paste was higher than that of HAp-type one. Furthermore, the hydrophilicity of the monetite-type paste was higher than that of HAp-type one. This suggests that starch-containing monetite-type bone pastes are expected to be partially replaced by autogenous bone as the hardened material is resorbed in vivo.

We synthesized Tb-doped potassium borosilicate glasses using the melt-quenching method for application in personal dosimeters. Photoluminescence (PL) and thermoluminescence (TL) were observed and were attributed to the 4f-4f transitions of Tb³⁺ ions. The concentration dependence of PL and TL properties was investigated by varying the Tb concentration from 0 to 3.0 %. The quantum yield increased with rising Tb concentration. The PL decay time remained consistent across all Tb-doped samples with a typical value of ∼4.5 ms for Tb³⁺. The TL glow curves showed a glow peak at approximately 60 °C for all the samples. The 0.1 % sample showed the highest TL intensity. The dynamic range of the 0.1 % sample ranged from 0.01 mGy to 1 Gy.

Wet classification was carried out on α-silicon nitride powders prepared by different methods, and the amount of dissolved oxygen and surface oxygen was measured using carrier gas hot extraction method. As a result, the amount of surface oxygen varied systematically depending on the class. The thickness of the oxide layer estimated from the amount of surface oxygen was 0.2–0.5 nm, which was the same as the values reported by X-ray photoelectron spectroscopy and Auger electron spectroscopy. On the other hand, the amount of dissolved oxygen was almost constant regardless of the specific surface area. The powder prepared by direct nitridation method showed a lower amount of dissolved oxygen than the powders prepared by combustion synthesis method.