Journal of the Ceramic Society of Japan
vol. 134, no.7, 2026

Feature: Cutting edge research on electroceramics, 2025

◆Preface◆

https://doi.org/10.2109/jcersj2.134.P7-1

P7-1

◆Full papers◆

Evaluation of organic–inorganic hybrid ferroelectric TMCM-GaCl₄ synthesized via hand mixing

https://doi.org/10.2109/jcersj2.25176

Keigo Honda, Akihiro Fukui, Sou Yasuhara and Takuya Hoshina

425

Organic–inorganic hybrid ferroelectrics have attracted attention for their large piezoelectric voltage constant. They are generally synthesized using single-crystal growth methods. However, the slow crystal growth rate makes it difficult to synthesize the desired composition efficiently. Herein, we focused on mechanochemical synthesis, which enables the rapid synthesis of the target crystal phase. In this study, we confirmed the synthesis of [(CH₃)₃NCH₂Cl]GaCl₄ (TMCM-GaCl₄) powder by hand-mixing TMCM-Cl and GaCl₃. In addition, the dielectric properties of dense pellets fabricated by uniaxial pressing of the powder were evaluated, and the ferroelectric phase transition was confirmed. This study demonstrates that hand mixing, a simple solid-state reaction process, is an effective method for synthesizing organic–inorganic hybrid ferroelectric TMCM-GaCl₄ powder.

LDA-based machine learning force field for accurate electric-field-driven ferroelectric response in BaTiO₃

https://doi.org/10.2109/jcersj2.25164

Ryotaro Sahashi, Po-Yen Chen and Teruyasu Mizoguchi

431

Accurately modeling the electric-field response of BaTiO₃ (BTO) requires a faithful reproduction of its equilibrium lattice structure, because dielectric permittivity and polarization switching are highly sensitive to subtle variations in tetragonality and Ti–O displacements. However, commonly used GGA functionals, such as PBEsol, systematically overestimate lattice constants, leading to significant underestimation of dielectric constants. In contrast, the local density approximation (LDA) provides structural parameters—particularly the c/a ratio and atomic off-centering—in much closer agreement with experimental data, offering a more reliable foundation for quantitative dielectric modeling. In this work, we construct a high-quality LDA-based first-principles dataset for BTO and fine-tune a machine learning force field (MLFF) together with a Born effective charge (BEC) prediction model. This integrated framework enables large-scale electric-field-coupled molecular dynamics simulations that retain the structural fidelity of LDA while achieving near–first-principles accuracy at significantly reduced computational cost. The resulting simulations successfully reproduce key ferroelectric features, including polarization switching and P–E hysteresis loops, and yield dielectric constants that are substantially closer to experimental values than those obtained from GGA-based approaches. These results demonstrate that adopting LDA as the foundational electronic structure method is essential for quantitatively accurate modeling of dielectric and ferroelectric responses in BTO, and that combining LDA-consistent MLFF and BEC models provides an efficient route to large-scale electric-field simulations of perovskite oxides.

Room-temperature deposition of flexible SnS thin films via sulfur-plasma-based reactive sputtering

https://doi.org/10.2109/jcersj2.26002

Daiki Motai, Issei Suzuki and Takahisa Omata

439

Fabrication of crystalline sulfide thin films on polymer substrates is typically constrained by the low heat resistance of the polymers and the thermal expansion mismatch between the films and the substrates. In this study, crystalline tin(II) sulfide (SnS) thin films were deposited on polyethylene terephthalate (PET) substrates at room temperature by sulfur-plasma-based reactive sputtering using a metallic Sn target and a sulfur-plasma source. The resulting SnS thin films on the PET substrates possessed a crystal phase exhibiting a preferential orientation, and adhesion properties comparable to those of thin films deposited on SiO₂ glass. Bending tests indicated that the electrical resistance of the films remained stable down to a bending radius of 12 mm and showed robust durability under cyclic bending at a radius of 15.2 mm. These results confirm that the SnS thin films possess sufficient flexibility for practical applications, such as wearable devices and curved solar cells. The findings indicate that sulfur-plasma-based reactive sputtering provides a versatile and effective route for the direct integration of various sulfide semiconductors onto flexible substrates, accelerating the development of sulfide-based flexible electronics.

Ionic conductivity enhancement at phase boundaries achieved by two-phase coexistence of spinel and rock salt structures: mimetics for the anode material Li₄Ti₅O₁₂

https://doi.org/10.2109/jcersj2.26004

Sou Yasuhara, Toshiki Sugiura and Takuya Hoshina

444

Oxide solid electrolytes with high Li-ion conductivity are necessary for the realization of highly safe all-solid-state Li-ion batteries. Although oxide materials have been extensively investigated, no material with sufficient properties as a solid electrolyte has yet been achieved. Therefore, enhancing ionic conductivity in solid materials remains an important challenge. In this study, two-phase coexistence ceramics were prepared to mimic the conductivity enhancement observed in the anode material Li₄Ti₅O₁₂ with spinel and rock salt structures using Li-containing insulating materials. LiFe₅O₈ and Li₃NbO₄ are used as model spinel and rock salt-related structures, respectively. A two-phase separated dense ceramic was successfully prepared by using a conventional solid-state reaction. AC impedance measurements revealed a single semicircle component at room temperature, indicating ionic conductivity enhancement induced by two-phase coexistence. The ceramics with two-phase coexistence showed a conductivity on the order of 10⁻⁷ S/cm, about nine orders of magnitude higher than that of pure LiFe₅O₈ or Li₃NbO₄. These results suggest that the conductivity enhancement can be interpreted as mimetic to that observed in Li₄Ti₅O₁₂.

Substrate dependence on the growth of defective-wurtzite Al₂S₃ thin films using pulsed laser deposition

https://doi.org/10.2109/jcersj2.25171

Kosuke Ono, Kazuki Shitara, Hiroki Moriwake, Shinya Kondo and Tomoaki Yamada

449

Wurtzite ferroelectrics such as AlScN have been extensively studied in recent years because they promise the compatibility to semiconductor technologies. These materials have higher remanent polarization than that of perovskite ferroelectrics, however its coercive field is very large comparing to them. Defective-wurtzite Al₂S₃ has been expected to have ferroelectricity with relatively low switching barrier comparing to AlN by a theoretical calculation. To evaluate experimentally its ferroelectric properties in the future, the deposition and growth of Al₂S₃ thin films and its dependences of various substrates were studied using pulsed laser deposition. It was demonstrated that Al₂S₃ can be grown epitaxially on α-Al₂O₃(0001) and SrTiO₃(111) while Pt(111)/α-Al₂O₃(0001) is not applicable to the growth.

Dielectric response modulation in relaxor (Sr,Ba)Nb₂O₆ via engineered defect

https://doi.org/10.2109/jcersj2.25173

Ryusei Shiota, Takashi Teranishi, Shinya Kondo and Akira Kishimoto

455

Defect engineering provides an effective pathway to tune the dielectric response of relaxor ferroelectrics, yet the roles of individual defect species in tungsten bronze (TTB) systems remain unclear. Here, we investigated how engineered Ti–V_O ^{• •} defect dipoles and native oxygen vacancies introduced through reduction annealing modify the dielectric properties of relaxor (Sr_0.5,Ba_0.5)Nb₂O₆ (0.5-SBN). Ti loading forms stable defect dipoles that generate smaller polar nanoregions (PNRs), suppress their overgrowth, and increase the number of dynamically active PNRs at room temperature, leading to enhanced permittivity ε′ while preserving DC-bias stability and breakdown strength (E_B). Reduction annealing generates Nb⁴⁺-related local polarizations aligned with the external electric field, which strengthen dipole fluctuations and slightly increase ε′. Electron localization further relaxes the TTB-A2 site disorder–induced random fields, yielding a sharper dielectric peak and promoting more uniform PNR growth. Microwave dielectric spectroscopy combined with electromagnetic simulations revealed that the increases in ε′ for both Ti-loaded and reduced samples (0.5-SBNT and Reduced 0.5-SBN, respectively) originate predominantly from enhanced dipole polarization. Despite grain coarsening in 0.5-SBNT, the E_B remained unchanged, indicating that defect dipoles act as pinning centers that inhibit field-induced PNR aggregation. In reduced 0.5-SBN, E_B increased up to pO₀ = 4.3 × 10⁻³ atm owing to relaxed random fields, whereas excessive reduction reduced E_B through carrier-driven space-charge effects. These results demonstrate that precise control of defect species enables simultaneous optimization of ε′, DC-bias stability, and E_B in TTB-type relaxor ferroelectrics.

Ferroelectric properties and structural characteristics of Mn and Zr co-substituted ZnO thin films

https://doi.org/10.2109/jcersj2.25177

Masaki Tozuka, Tadaaki Kitahara, Sou Yasuhara and Takuya Hoshina

461

Wurtzite-type ferroelectrics have garnered significant attention as next-generation memory materials due to their high remanent polarization and excellent scalability. However, reported ZnO-based ferroelectrics exhibit high coercive fields close to their dielectric breakdown voltage, resulting in poor insulation reliability. In this study, we investigated the effects of Mn and Zr co-substitution into Zn sites to identify new dopants capable of inducing observable ferroelectricity in ZnO. Thin films with compositions of Zn_1−x(Mn,Zr)_xO (x = 0–0.20) were fabricated using pulsed laser deposition. X-ray diffraction analysis confirmed that both the c-axis length and the c/a ratio increased with the substitution concentration. Furthermore, polarization–electric field measurements successfully revealed distinct ferroelectric hysteresis loops for the compositions at x = 0.10 and x = 0.15. Although conventional ZnO-based ferroelectrics were reported to show the ferroelectricity by decrease of the c/a ratio, Zr and Mn co-substitution was revealed to induce ferroelectricity with an increase of the c/a ratio.

Melt-quenching synthesis and spectral tuning of a new green-emitting phosphor Ba₁₀Y₂₆Si₁₆O₈₁:Eu²⁺

https://doi.org/10.2109/jcersj2.25174

Wataru Hikita and Kenji Toda

467

A new green-emitting phosphor Ba₁₀Y₂₆Si₁₆O₈₁:Eu²⁺ was successfully synthesized via a melt-quenching technique. The crystal structure of the Ba₁₀Y₂₆Si₁₆O₈₁:Eu²⁺ phosphor was confirmed by single-crystal X-ray diffraction (XRD) analysis. The photoluminescence (PL) characterization revealed that the Ba₁₀Y₂₆Si₁₆O₈₁:Eu²⁺ phosphors exhibit yellowish green emission peaking at about 540 nm under near-UV (n-UV) irradiation. The emission spectra can be tuned by the incorporation of Mg²⁺ ions.

Fundamental properties of novel zero-dimensional halide Na₂HfI₆ and application for neutron detection by Li doping

https://doi.org/10.2109/jcersj2.25178

Chihaya Fujiwara, Shunsuke Kurosawa, Akihiro Yamaji, Akira Yoshikawa, Nishiki Matsubayashi, Takushi Takata and Hiroki Tanaka

475

Zero-dimensional (0D) metal halide scintillators have attracted considerable attention owing to their exceptional emission properties derived from strongly localized self-trapped excitons. In this paper, we report the development of a novel thermal neutron scintillator—Na_2−xLi_xHfI₆ (0 ≤ x ≤ 2)—achieved by strategically substituting lithium for the Na of the 0D Na₂HfI₆ host. The Na₂HfI₆ host material has a 0D structure with an [HfI₆]²⁻ octahedral unit, exhibiting broad red-to-near-infrared (NIR) emission with a large stokes shift, driven by strong electron–phonon coupling (S = 56.7) and high exciton binding energy (E_b = 200 meV). Density functional theory calculations revealed that the A site cations (Na⁺ and Li⁺) did not contribute to the valence or conduction band edges. This indicated that the fundamental electronic structure was preserved upon Li substitution; consequently, the Li-alloyed Na_2−xLi_xHfI₆ also exhibited the characteristic broad red-to-NIR emission. Remarkably, the Na_1.5Li_0.5HfI₆ crystal demonstrated a light yield of 37,000 ph./n_th under thermal neutron irradiation, approximately six times higher than that of the standard ⁶Li glass scintillator (GS20). With the fast decay time (650 ns) as red/NIR emission, high light output, and red/NIR emission wavelength, Na_2−xLi_xHfI₆ offers a robust and high-performance alternative material to conventional scintillators.

Regular Issue

◆Full papers◆

Phase transformation kinetics and mechanism of polycrystalline Sr-hexacelsian to celsian

https://doi.org/10.2109/jcersj2.26012

Yuichi Kobayashi, Masatomo Hattori and Akitoshi Imagawa

483

The isothermal transformation of Sr-hexacelsian to celsian in sintered bodies having chemical composition xSrO·Al₂O₃·2SiO₂ (x = 1.0, 1.1 and 1.2) was analyzed using X-ray diffraction and JMA kinetics. All compositions showed rapid initial transformation followed by strong deceleration, and excess SrO accelerated the reaction. JMA plots exhibited two linear regions, indicating a mechanism change caused by crack formation at the advancing transformation front. Significant volume contraction, enhanced at high temperature due to thermal-expansion mismatch, generated internal stresses that promoted cracking and constrained later-stage growth. The Avrami index increased from 1.5 to about 2 with temperature, consistent with a shift from one-dimensional to two-dimensional growth. High activation energies (833–934 kJ/mol) were attributed to stress interactions between anisotropic hexacelsian grains.

Effect of α-MgO/MgSO₄, sodium citrate, and calcium stearate on the properties of magnesium oxysulfate foam concrete

https://doi.org/10.2109/jcersj2.25095

Panpan Liu, Zhen Wang, Huibing Zhao, Wenjuan Fan, Wei Wang and Yangyang Xue

490

Leveraging the unique advantages of magnesium sulfate cement (MOS) and advancements in insulation materials, this study investigates the preparation of magnesium oxysulfate cement foam concrete (MOSFC) using a chemical foaming method, aiming to achieve rapid solidification and high early strength. To systematically assess its mechanical and physical properties, the effects of modifier (sodium citrate) and foam stabilizer (calcium stearate) content on basic MOSFC were examined. Key performance metrics, including 28-day compressive strength, thermal conductivity, volumetric water absorption, softening coefficient, and microscopic morphology, were evaluated. The results indicate that at a molar ratio of α-MgO/MgSO₄ = 6, MOSFC achieves optimal compressive strength and minimal thermal conductivity. The hydration behavior of these mixtures in the MOSFC slurry governs its performance, primarily influenced by three factors: slurry apparent density, internal pore structure, and the bonding interactions among the solid, gas, and liquid phases.

Abnormal delay in precipitation of magnesium oxalate with aged solutions

https://doi.org/10.2109/jcersj2.26023

Miri Kusano, Naoya Enomoto and Yuta Tsuji

502

Precipitation behavior of magnesium oxalate using oxalic acid dissolved in water/ethanol (W/E) solvents was investigated. This study examined the effects of various process parameters, including solvent composition, aging time of the starting solution, aging temperature, and alcohol species. Special attention was given to the delay time (incubation period, IP), defined as the time from solution mixing to the appearance of turbidity. A remarkably long delay exceeding 4 days was observed at W/E = 0/10 and with an aging time of 14 days. Regarding the solvent composition, an unexpected minimum point for IP was observed at W/E = 1/9. Furthermore, the addition of fresh oxalic acid to the aged solution drastically decreased the IPs. Molecular dynamics (MD) simulations qualitatively suggested that monovalent oxalic acid (HC₂O₄⁻) may experience locally hindered diffusion in pure ethanol. These findings suggest that oxalic acid, while appearing highly soluble macroscopically, might not exhibit similar solubility at the microscopic level, influencing the precipitation kinetics.

Effect of heat-treatment atmosphere on structural properties of Li–Y–Cl solid electrolytes

https://doi.org/10.2109/jcersj2.26028

Hirotada Gamo, Kaito Fujita and Tatsuo Noda

509

Chloride-based solid electrolytes (SEs) exhibit high ionic conductivity and wide electrochemical stability windows, which have attracted much attention as ion conductors in all-solid-state lithium-ion batteries. However, a scalable liquid-phase synthesis method for highly conductive chloride SEs has not yet been established owing to a limited understanding of the effects of synthesis conditions on structural properties. In this study, highly crystalline orthorhombic Li–Y–Cl SEs were synthesized via a pyridine-mediated liquid-phase synthesis method followed by post-heat treatment under an Ar atmosphere. The synthesized Li_2.5YCl_5.5 exhibited an ionic conductivity of 2.2 × 10⁻⁴ S cm⁻¹ at 25 °C and oxidation stability up to 3.14 V versus Li–In. X-ray photoelectron spectroscopy analysis revealed that heat treatment under an Ar atmosphere suppresses Cl release during crystallization, leading to the formation of a highly crystalline orthorhombic phase. This study provides important insights into the role of atmosphere control in the crystallization process of chloride SEs.

Electronic structure and optical properties of the green pigment Y₂BaCuO₅: A many-body perturbation theory study

https://doi.org/10.2109/jcersj2.26026

Shigenori Matsushima, Taiyo Inada, Sota Kimura, Junko Ishii and Masao Arai

514

Y₂BaCuO₅ (YBC211) is renowned as an environmentally benign inorganic pigment distinguished by its brilliant green coloration. However, conventional first-principles band calculations, such as those based on the generalized gradient approximation (GGA), fail to describe its optical properties due to the systematic underestimation of the band gap and the inadequate description of strongly correlated Cu 3d electrons. In this study, we investigated the electronic structure and optical properties of YBC211 using a high-precision computational framework that integrates the HSE06 hybrid functional, the G₀W₀ approximation, and the Bethe-Salpeter equation (BSE). To elucidate the microscopic origin of the coloration, the frequency-dependent complex dielectric function, ε(ω) = ε₁(ω) + iε₂(ω), was calculated. While the HSE06 functional improves the electronic structure description compared to GGA, it overestimates the optical gap by approximately 1 eV. Furthermore, the G₀W₀ calculation, which accounts for the quasiparticle self-energy but neglects electron–hole interactions, further shifts the onset of the imaginary part of the dielectric function (ε₂) toward higher energies. By solving the BSE to incorporate many-body excitonic effects, we demonstrate that the strong Coulomb attraction between electrons and holes within the distorted [CuO₅] clusters induces a dramatic redshift of the absorption peak to approximately 2.0 eV. The chromaticity coordinates derived from the calculated spectra quantitatively reproduce the characteristic vivid green color. These results indicate that the optical response of YBC211 is governed by strongly bound excitons stabilized by significant electron correlations.

Novel Mn³⁺-doped Na₃Ga(PO₄)₂ violet pigment based on trigonal bipyramidal coordination environment

https://doi.org/10.2109/jcersj2.26027

Wataru Hikita and Kenji Toda

521

Inorganic pigments are widely used; however, many pigments contain toxic elements such as cobalt. Recently, Mn³⁺-introduced pigments utilizing a trigonal bipyramidal coordination environment have gained significant attention as low-toxic alternatives to cobalt-based blue or violet pigments. In this study, we successfully synthesized Mn³⁺-doped Na₃Ga(PO₄)₂ pigment as a novel violet color source. The optical properties were evaluated using diffuse reflectance spectra and absorption spectra obtained by ultraviolet–visible (UV–Vis) spectroscopy. The optimized sample exhibited a vivid violet color with a reflection peak observed around 410–420 nm. In addition, Mn³⁺-doped Na₃Ga(PO₄)₂ demonstrated high chemical stability in distilled water and weak alkaline solution.

Effect of surface modification on anion conductivity of layered double hydroxide nanoparticles for anion exchange membrane water electrolysis

https://doi.org/10.2109/jcersj2.26019

Hirofumi Osato, Shigenori Mitsushima and Yoshiyuki Kuroda

526

Anion exchange membrane water electrolysis (AEMWE) is promising because of the cost-effectiveness of catalysts and high energy efficiency. Oxidative degradation of ionomers is one of the most important issues in AEMWE. The use of layered double hydroxide nanoparticles (LDH nanoparticles) is promising to protect ionomers from direct oxidation on electrocatalysts. Here, the effect of surface modification of LDH nanoparticles on ionic conductivity was investigated. LDH nanoparticles with various degrees of surface modification with tris(hydroxymethyl)aminomethane (Tris-NH₂) were compared with conventional non-modified LDHs. The deconvoluted ATR-FTIR spectra showed C–O stretching bands of interlayer CO₃²⁻ with no apparent hydrogen bond with other species (CO₃²⁻-free). The decrease of absorbance of H–O–H bending band is correlated with the increase in hydrogen bond with other species. The fraction of CO₃²⁻-free increased and the absorbance of H–O–H bending band decreased along with the increase in the amount of Tris-NH₂ modified on LDH nanoparticles, showing the surface modification weaken hydrogen bond among interlayer water, CO₃²⁻ and surface hydroxy groups. The ionic conductivities of modified LDH nanoparticles and conventional LDHs were measured, using a water electrolysis cell under liquid water feed. The increase in the amount of Tris-NH₂ was correlated with the increase in the ionic conductivity of LDH nanoparticles, whereas a large interparticle resistance was observed for LDH nanoparticles. The very small size of the surface-modified LDH nanoparticles makes them unique toward their use for ionomer protection in AEMWE.

Alumina precipitation in rutile single crystal saturated with alumina under thermal tensile stress

https://doi.org/10.2109/jcersj2.26020

Yutaka Ohya, Wingki Mey Hendra and Chika Takai-Yamashita

534

Alumina precipitation behavior in rutile single crystals saturated with alumina was investigated using diffusion couples composed of rutile a-plane bonded to corundum c-plane. During annealing at 1200–1300 °C, alumina dissolved into rutile according to the defect reaction, Al₂O₃ \to 2Al′_Ti + 3O_O ^× + V_O ^{· ·} . Subsequent cooling generated supersaturation of alumina and, simultaneously, produced significant tensile stress along the rutile c-axis due to the mismatch in thermal contraction between rutile and corundum. This stress induced dislocation formation having slip system, such as (011)[0−11]. In the air-quenched samples, supersaturated oxide-ion vacancies reacted with screw dislocations directed [101] and [10−1] on the (100) plane, to form rectangular helical and/or zigzag dislocations. Alumina precipitated along these modified dislocations as corundum. The direction of the rectangular helical and zigzag modifications associated with the pseudo-hexagonal oxide-ion sublattice of rutile. In contrast, slow cooling at 10 °C/min produced four-lobed corundum precipitates aligned with the rutile a- and b-axes, corresponding to half of the eight-lobed morphology. These results demonstrate that thermal stress, cooling rate, and crystallographic orientation jointly control modification of dislocation structures and alumina precipitation morphology in alumina-saturated rutile.

◆Announcement◆

Call for a Guest Editor for a Special Issue

https://doi.org/10.2109/jcersj2.134.A7-1

A7-1

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