Journal of the Ceramic Society of Japan
Online ISSN : 1348-6535
Print ISSN : 1882-0743
ISSN-L : 1348-6535
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Feature: Cutting edge research on electroceramics 2019: Preface
Feature: Cutting edge research on electroceramics 2019: Full papers
  • Yusuke IGUCHI, Tomoaki YAMADA, Osami SAKATA, Masahito YOSHINO, Takanor ...
    2020 Volume 128 Issue 8 Pages 431-435
    Published: August 01, 2020
    Released: August 01, 2020
    JOURNALS FREE ACCESS

    Artificial superlattice thin films of (Pb0.9Sr0.1)TiO3 (PST)n/SrTiO3 (STO)m were grown on SrRuO3-electroded DyScO3 (001)pc substrates by pulsed laser deposition. X-ray diffraction (XRD) showed that the fabricated superlattice thin films have a good periodicity in the out-of-plane direction, indicating the sharp interfaces regardless of the difference in layer thickness. Synchrotron XRD indicated that the film with n/m = 14/20 had a weak periodicity in the in-plane direction, which may had arisen from the ordered polar vortex arrays existing in the PST layers. All the fabricated superlattice thin films showed the electric field-induced strain, though its magnitude was smaller than that for typical ferroelectric materials.

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  • Hiroki TANAKA, Kiyoshi UCHIYAMA, Takao SHIMIZU, Hiroshi FUNAKUBO
    2020 Volume 128 Issue 8 Pages 436-440
    Published: August 01, 2020
    Released: August 01, 2020
    JOURNALS FREE ACCESS

    A SrZrO3 thin film with yttrium (Y) concentration of 20 at % (SZYO) was successfully deposited by the pulsed laser deposition (PLD) technique. The laser power of PLD affected Y-concentration significantly even though it used the same PLD target. On contrary, the laser reputation frequency and the deposition temperature did not significantly affect the composition. The SZYO film deposited at the optimized conditions was well crystallized and showed no secondary phase and showed (111) and (110) orientations when they were deposited on (111)Pt/SiOx/Si and on (111)Pd/(111)Pt/SiOx/Si substrates, respectively. This SZYO film is expected to use as an electrode of our proposed novel solid oxide fuel cells.

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  • Haruki USUI, Hiraku KUSAKABE, Makoto TOKUDA, Kazumasa SUGIYAMA, Takuya ...
    2020 Volume 128 Issue 8 Pages 441-446
    Published: August 01, 2020
    Released: August 01, 2020
    JOURNALS FREE ACCESS

    Ba3TaGa3Si2O14 (BTGS) bulk single crystals were grown by the Czochralski method. The crystal structure of BTGS has been refined using single-crystal X-ray diffraction data with a precision corresponding to an R index of 0.018. The crystal structure is isostructural to La3Ga5SiO14 which has the trigonal space group P321 and Z = 1, and the distribution of each cation is ordered in each site. Material constants and resistivity of the crystal were measured up to 550 °C. The results indicate that the BTGS crystal is a good candidate for piezoelectric applications in elevated temperatures.

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  • Takuo TOMINAGA, Yuka TAKAGI, Hajime NAGATA, Tadashi TAKENAKA
    2020 Volume 128 Issue 8 Pages 447-452
    Published: August 01, 2020
    Released: August 01, 2020
    JOURNALS FREE ACCESS

    Doping effects of Mn and Cu ions for (1 − x)Ba(Zr0.2Ti0.8)O3x(Ba0.7Ca0.3)TiO3 [BZT–xBCT] ceramics were investigated with the aim for high-power piezoelectric characteristics such as vibration velocity v0–p, mechanical quality factor Qm and piezoelectric constant d31 at large amplitude vibration. The v0–p is well known as proportional to a product of small signal d31 and Qm [d31 × Qm]. BZT–0.6BCT based ceramics were prepared by conventional solid-state reaction method. In the case of CuO doping, both d31 and Qm values were simultaneously improved by the doping amount of 0.1 wt % to BZT–0.6BCT ceramics, then the d31 × Qm value was 3 times larger than that of non-doped BZT–0.6BCT ceramics. On contrary to the case of co-doping of CuO and MnCO3, MnCO3 0.6 wt % and CuO 0.1 wt % added BZT–0.6BCT ceramics showed significant improvement of Qm, then the d31 × Qm value was approximately 6 times larger than that of non-doped BZT–BCT ceramics. The v0–p of BZT–0.6BCT ceramics doped with MnCO3 1.0 wt % and CuO 0.1 wt % was increased significantly, which was larger than that of Pb(Zr,Ti)O3-based ceramics. Temperature dependence of v0–p was also investigated, and it was stable up to 80 °C. It was supposed availability of practical high-power piezoelectric applications at around room temperature.

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  • Tsuyoshi TAKAMI, Yoshihisa ISHIKAWA, Masao YONEMURA, Toshiharu FUKUNAG ...
    2020 Volume 128 Issue 8 Pages 453-456
    Published: August 01, 2020
    Released: August 01, 2020
    JOURNALS FREE ACCESS

    Oxide electrolytes are a growing topic in battery research, but their full potential has not yet been realized owing to the lack of new materials. As opposite to the traditional design strategy that relies on d0 or d10 systems, we focus our attention on 3d6 systems, oxygen-excess La2−yLixLi0.5Co0.5O4.25 and oxygen-deficient La4/3−xLi3x+yLi0.5Co0.5O4−δ. Among them, we achieve lithium-ion conduction in La1.24Li0.57Li0.5Co0.5O3.15. A quasi-one dimensional pathway for lithium diffusion or distortion of lithium nuclear density is confirmed to be present at 100 °C by analyzing neutron powder diffraction data in combination with the maximum entropy method.

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  • Hiroki ISHIGAMI, Takahiko KAWAGUCHI, Naonori SAKAMOTO, Shenglei CHE, N ...
    2020 Volume 128 Issue 8 Pages 457-463
    Published: August 01, 2020
    Released: August 01, 2020
    JOURNALS FREE ACCESS

    Polycrystalline ZnFe2O4 thin films were deposited on Si and porous Si (PSi) substrates using Dynamic Aurora pulsed laser deposition (PLD in a magnetic field). The average grain sizes of ZnFe2O4/Si and ZnFe2O4/PSi were, respectively, 120 and 48 nm. The ZnFe2O4/PSi thin film resistance was higher than that of ZnFe2O4/Si thin film. For ZnFe2O4/Si and ZnFe2O4/PSi thin films, the sensor response for liquefied petroleum gas was measured as a function of time and temperature. The sensor response of ZnFe2O4/PSi thin film measured at 375 °C is higher than that of ZnFe2O4/Si thin film. Results showed a steep initial rise in the temperature dependence of ZnFe2O4 thin films prepared using PLD. The dependence is steeper than that reported for ZnFe2O4 powder or thick and thin films prepared using chemical processing.

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  • Asuka TSUJII, Takashi KASASHIMA, Masato YAMAZAKI, Yasuyuki OKIMURA
    2020 Volume 128 Issue 8 Pages 464-468
    Published: August 01, 2020
    Released: August 01, 2020
    JOURNALS FREE ACCESS

    Ultrasonic sensors fabricated using (K,Na)NbO3–KTiNbO5 (KNN–NTK)-based lead-free piezoelectric ceramics were fabricated, their sensor characteristics were compared with those of sensors fabricated using Pb(Zr,Ti)O3 (PZT)-based piezoelectric ceramics, and effects of material properties on sensor performance were investigated. The sound pressure, sensitivity, temperature increase during driving, and the responsiveness of the KNN–NTK-based sensor equaled those of the PZT-5A-based sensor. PZT-5A is generally used for ultrasonic sensors and has the same mechanical quality factor Qm as the KNN–NTK ceramics. Most sensor characteristics are explained based on the electromechanical coupling factor and Qm. However, the change in frequency characteristics under high applied power was observed that is attributed to the tendency of the nonlinear phenomenon of KNN–NTK-based ceramics to be weaker than that of PZT-based ceramics.

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  • Hari Shankar MALLIK, Ichiro FUJII, Gopal Prasad KHANAL, Sangwook KIM, ...
    2020 Volume 128 Issue 8 Pages 469-474
    Published: August 01, 2020
    Released: August 01, 2020
    JOURNALS FREE ACCESS

    ⟨111⟩-oriented BaTiO3 (BT) ceramics were prepared by a high magnetic field assisted electrophoretic deposition method using hexagonal-tetragonal co-existing BT powders. With increasing the hexagonal content, the ⟨111⟩-orientation factor increased, while piezoelectric strain constant d*33 increased up to the hexagonal content of 80% with attaining a maximum value of 627 pm V−1 and then rapidly decreased. In contrast, the decreasing trend of d*33 with increasing hexagonal content in the randomly oriented ceramics was observed. These results were discussed with the degree of the orientation and the possible twin defects in the BT ceramics.

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  • Ken-ichi MIMURA, Zheng LIU, Hiroki ITASAKA, Kazumi KATO
    2020 Volume 128 Issue 8 Pages 475-480
    Published: August 01, 2020
    Released: August 01, 2020
    JOURNALS FREE ACCESS

    A-site substituted (Ba1−x,Srx)TiO3 nanocubes (BSxT NC; x is Sr ratio) were synthesized by hydrothermal process with surfactant and additives. X-ray diffraction profiles of BSxT NCs showed single-phase of perovskite. Size of BSxT NCs was decreased with increasing Sr content under same hydrothermal condition. When synthesis temperature increased, size of BSxT NCs was enlarged. It revealed that the size of BSxT NCs was able to be controlled by optimizing the hydrothermal conditions. However, inhomogeneous substitution was observed by scanning transmission electron microscopy with energy dispersive X-ray spectroscopy. It suggested that reaction rate of Sr ions to form perovskite structure was faster than that of Ba ions under hydrothermal condition. Three-dimensional (3D) assemblies of BSxT NCs after heat-treatment at 850 °C had obscured interfaces between the NCs. Raman spectroscopy of NC assemblies revealed that symmetry of BSxT NCs differed from that of BaTiO3 (BT) NCs and did not change after heat-treatment at 850 °C. Piezoresponse curves became slim hysteresis behavior with increasing Sr ratio. These results suggested that Sr substitution of BT NCs caused phase transition from ferroelectric to paraelectric phase in 3D assemblies.

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  • Shuya MINEGISHI, Takuya HOSHINA, Takaaki TSURUMI, Kheirreddine LEBBOU, ...
    2020 Volume 128 Issue 8 Pages 481-485
    Published: August 01, 2020
    Released: August 01, 2020
    JOURNALS FREE ACCESS

    Single crystals of LixLa(1−x)/3NbO3 were grown in air using Czochralski method from La-poor melt. The lithium-ion conductivity of the crystals was measured. The length and maximum diameter of the boule grown were 23 and 20 mm, respectively. The boule contained no inclusions but was covered with a very thin polycrystalline film of LaNbO4 and LiNbO3 in its upper region. The composition of the crystals grown was estimated to be x = 0.15 and the starting melt composition was x = 0.20. The ionic conductivity of the crystal was anisotropic with σ[100] = 2.8 × 10−4 S cm−1 and σ[001] = 9.7 × 10−5 S cm−1 at 306 K. The activation energy, Ea of these conductivities was almost the same in the range of 0.28–0.29 eV. Further, we discussed the anisotropic lithium-ion conductivity of the crystal.

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  • Takahiro YAMADA, Hiroaki TAKEDA, Takaaki TSURUMI, Takuya HOSHINA
    2020 Volume 128 Issue 8 Pages 486-491
    Published: August 01, 2020
    Released: August 01, 2020
    JOURNALS FREE ACCESS

    The possibility of bismuth (Bi) and nitrogen (N) co-doped barium titanate (BaTiO3) as a ferroelectric material was investigated by calculation and experiment. From first principles calculations, it was found that Bi and N co-doped BaTiO3 has a higher spontaneous polarization than undoped BaTiO3 since dopant Bi and N ions contribute to the enhancement of covalent interactions between cations and anions. Because it was revealed that the ferroelectricity of BaTiO3 can be improved by co-doping of Bi and N, we demonstrated the synthesis of (Ba,Bi)Ti(O,N)3. Single phase oxynitride (Ba,Bi)Ti(O,N)3 powder was fabricated by annealing (Ba,Bi)TiO3 in NH3 gas. The tetragonal distortion of (Ba,Bi)Ti(O,N)3 was smaller than that of BaTiO3, which may be due to A-site and O-site vacancies in the perovskite lattice introduced during NH3 annealing.

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  • Takumi SHIMIZU, Takanori KIGUCHI, Takahisa SHIRAISHI, Toyohiko J. KONN ...
    2020 Volume 128 Issue 8 Pages 492-500
    Published: August 01, 2020
    Released: August 01, 2020
    JOURNALS FREE ACCESS

    The interface structure change between PbTiO3 (PTO) thin films with various thickness grown on La-doped SrTiO3(001) (La:STO) single crystal substrates by chemical solution deposition method was elucidated by (scanning) transmission electron microscopy ((S)TEM). The films were comprised of perovskite single phase and cube-on-cube orientation relationship with the substrate. STEM images revealed that the twin deformation precedes the nucleation of edge dislocations away from the coherent interface between the film and the substrate. Diffusion of Pb ions into the substrate was also observed through edge dislocations away from the interface. Edge dislocations climbs downward into the substrate with further diffusion of Pb ions increasing the film thickness. This phenomenon was not observed in the PTO film deposited on the non-doped STO substrate. Therefore, lattice defects in the La:STO substrate. the misfit dislocation induced by 90° domain formation as well as similar ionic radius between Pb and Sr ions appeared to facilitate the local interdiffusion of the constituent elements between the film and the substrate.

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  • Takanori KIGUCHI, Takumi SHIMIZU, Takahisa SHIRAISHI, Toyohiko J. KONN ...
    2020 Volume 128 Issue 8 Pages 501-511
    Published: August 01, 2020
    Released: August 01, 2020
    JOURNALS FREE ACCESS

    Using scanning transmission electron microscopy and electron energy loss spectroscopy, we have elucidated the local structure and the crystallization mechanism of amorphous phase PbZrxTi1−xO3 (PZT) (x = 0.3) thin films deposited on SrTiO3 (STO) (001) single-crystal substrates by chemical solution deposition. The amorphous phase involves the short-range order of (Ti/Zr)O6 octahedra and Pb–O, and then, they are connected with the residual carbon. During the pyrolysis process, the first unit cells of the film has already crystallized with cube-on-cube epitaxial relationship with the STO substrate. The film–substrate interface is coherent and atomically sharp between the first Pb–O layer and the substrate. In the crystallization process, this layer seems to act as a seed layer for PZT epitaxial film growth. It accelerates crystal growth as a nucleation site and simultaneously shrinks the film by combustion of the residual carbon and subsequent densification, affecting the local coordination structure in the amorphous phase. The self-organized seed layer in the pyrolyzed film appears to play an important role in the epitaxial growth.

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  • Yoshiharu ITO, Akinori TATEYAMA, Yoshiko NAKAMURA, Takao SHIMIZU, Mino ...
    2020 Volume 128 Issue 8 Pages 512-517
    Published: August 01, 2020
    Released: August 01, 2020
    JOURNALS FREE ACCESS

    (K,Na)NbO3 thick films were prepared at 240 °C on (100)cSrRuO3//(100)SrTiO3 substrates by hydrothermal method. Film thickness increased using an amorphous niobium source instead of conventionally used crystalline one and have the maximum thickness at 0.5 mmol of input mass of niobium source within the range of 0.02–7.5 mmol in case of the 20 h deposition. The yield of (K,Na)NbO3 films from 0.5 mmol amorphous niobium source becomes 20 times higher than that from conventionally used a 2 mmol crystalline niobium source. In addition, crystal structure, surface morphology, dielectric constant, and ferroelectric and piezoelectric properties of these films were almost independent of the kinds of niobium sources and their input mass within the limitation of the present results.

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  • Hirotaka HARA, Chao-Nan XU, Ruiping WANG, Xu-Guang ZHENG, Maiko NISHIB ...
    2020 Volume 128 Issue 8 Pages 518-522
    Published: August 01, 2020
    Released: August 01, 2020
    JOURNALS FREE ACCESS

    Piezoelectric LiNbO3:Pr3+ has recently attracted attention as a so-called multi-piezo material, exhibiting simultaneously piezoluminescence and piezoelectricity. In order to investigate and improve the performance of piezoluminescence and piezoelectricity in the newly found multi-piezo material LiNbO3:Pr3+, a systematic study has been carried out on both the crystal structural stability and the correlated multi-piezo performance through structure control between LiNbO3 and NaNbO3. Full set samples of Li1−xNaxNbO3:Pr3+ (x = 0–1) with various Li/Na ratios were synthesized, and the crystal structure, piezoluminescence performance, piezoelectric property d33, and their correlations were systematically investigated. We found that four crystal phases, LiNbO3-R3c, NaNbO3-R3c, NaNbO3-P21ma, NaNbO3-Pbma, can exist stably with co-existence in Li1−xNaxNbO3:Pr3+ by controlling the Li/Na ratio. A strong correlation between piezoluminescence and piezoelectric properties was verified. Furthermore, the highest piezoluminescence intensity and piezoelectric constant were realized near the phase boundary of NaNbO3-R3c and NaNbO3-P21ma, demonstrating the crystal structure control as a promising technology to engineer multi-piezo materials.

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  • Miki ARAI, Yutaka FUJIMOTO, Masanori KOSHIMIZU, Ichiro KAWAMURA, Daisu ...
    2020 Volume 128 Issue 8 Pages 523-531
    Published: August 01, 2020
    Released: August 01, 2020
    JOURNALS FREE ACCESS

    CaS-based materials are known as highly efficient phosphors. CaS has excellent properties as host materials of phosphors under ultraviolet irradiation and is expected to have also for radiation detection. In this study, we fabricated CaS ceramic phosphors and measured their photoluminescence (PL), scintillation, and dosimetry characteristics to investigate the applicability of CaS ceramics as scintillators and dosimeters. The scintillation emission spectrum of CaS:Eu ceramics showed an emission peak at 656 nm, originating from the 5d–4f transitions od Eu2+ ions. The scintillation emission spectrum of CaS:Ce ceramics showed emission peaks at 510 and 570 nm that originate from the 5d–4f transitions of Ce3+ ions. The PL emission peaks of CaS:Ce and CaS:Eu were similar to those of the X-ray-induced radioluminescence emission peaks and were also assigned to the emission of Ce3+ and Eu2+ ions. The light yield of CaS:Ce and CaS:Eu were estimated to be approximately 1,700 and 4,400 photons/MeV, respectively. As for CaS:Eu, significant afterglow and strong thermoluminescence were observed, which indicates the sample contained trap sites at high concentration. Considering their PL, thermoluminescence, and scintillation properties, CaS:Ce and CaS:Eu have potentials for application as scintillators and dosimeters, respectively.

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  • Kasumi MOTOMIYA, Manabu HAGIWARA, Shinobu FUJIHARA
    2020 Volume 128 Issue 8 Pages 532-538
    Published: August 01, 2020
    Released: August 01, 2020
    JOURNALS FREE ACCESS

    YVO4:Eu3+ phosphor particles are proposed as an H2O2 sensing material based on their turn-off luminescence. The YVO4:Eu3+ particles having various surface microstructures were synthesized through liquid processes and their H2O2 sensing ability was evaluated by immersing them in an aqueous H2O2 solution with a constant volume at a fixed concentration. The microstructures were characterized in detail not only by electron microscopy but also by nitrogen adsorption to elucidate factors governing the H2O2 sensing ability. It was then indicated that micro-/mesoporous structures, which were introduced in the micrometer-scaled spherical particles during their synthesis by a biphasic sol–gel method, were a decisive factor for achieving the effective H2O2 sensing. The YVO4:Eu3+ particles synthesized under the improved condition could show a 37% decrease of luminescence intensity after the H2O2 treatment.

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  • Reijiro SHIMURA, Takanori MIMURA, Takao SHIMIZU, Yoshitomo TANAKA, Yuk ...
    2020 Volume 128 Issue 8 Pages 539-543
    Published: August 01, 2020
    Released: August 01, 2020
    JOURNALS FREE ACCESS

    Y-doped HfO2 films with various thicknesses were prepared on (100)-oriented [10 wt.% Sn-doped In2O3, ITO]//(100) [yttria-stabilized zirconia, YSZ], and (111)ITO//(111)YSZ substrates by a radio-frequency magnetron sputtering method. Almost a single phase of orthorhombic symmetry was obtained for all films. {100}-oriented epitaxial films were obtained on (100)ITO//(100)YSZ substrates, while the film orientation changed from {111} to {100} with increasing film thickness on (111)ITO//(111)YSZ substrates. {100}-oriented epitaxial Y-doped HfO2 films were also obtained on (100)-oriented epitaxial ITO layers on (100)YSZ//(001)Si substrates. Ferroelectricity was observed for all films. Their remanent polarization (Pr) and coercive fields (Ec) were about 5 µC/cm2 and 1 MV/cm, respectively, indicating that Pr and Ec were almost independent of the film thickness and kind of substrate.

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Feature: Cutting edge research on electroceramics 2019: Note
  • Yoshiharu MATSUMAE, Ryuya SUZUKI, Kazuki KOMIYA, Masashi HIGUCHI
    2020 Volume 128 Issue 8 Pages 544-546
    Published: August 01, 2020
    Released: August 01, 2020
    JOURNALS FREE ACCESS

    Sodium manganese oxide for a cathode material of sodium-ion secondary battery was rapidly synthesized in 5–15 min by an improved microwave heating method with boron addition. Although prepared cathode materials included three types of NaXMnO2, it exhibited good electrochemical performance and delivered an initial discharge capacity of 200 mA h g−1 at second discharge. Electrochemical activation of β-NaMnO2 to α-NaMnO2 during charge–discharge process was indicated by X-ray diffraction results.

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Regular Issue: Special Article: The 74th CerSJ Awards for Academic Achievements in Ceramic Science and Technology: Review
  • Masanori KIKUCHI
    2020 Volume 128 Issue 8 Pages 547-554
    Published: August 01, 2020
    Released: August 01, 2020
    JOURNALS FREE ACCESS

    Calcium phosphate-based bone regenerating materials were developed by utilizing interfacial interaction between inorganic–organic substances. Although apatitic calcium phosphates, hydroxyapatite (HAp) and β-tricalcium phosphate (β-TCP), have unique affinity to organic substances, and utilization of the affinity requires appropriate surrounding conditions. The author and his colleagues control the surrounding conditions to realize porous HAp ceramics with high porosity, interconnectivity and compressive strength, composite membrane of β-TCP and polylactide-based biodegradable polymers for guided bone regeneration, and bone-like nanocomposite of HAp and type-I atelocollagen (HAp/Col). Electrostatic interactions between calcium phosphates and polymers in these composites were presented by reflection infrared spectra. They also examined in vitro and in vivo and demonstrate good bone regeneration properties. Particularly, the HAp/Col exhibits completely incorporation into bone remodeling process that is the first in the world for synthetic materials. Three of these materials are also commercialized and used in medical and dental fields and contribute to human health.

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Regular Issue: Full papers
  • Tansza Setiana PUTRI, Yuki SUGIURA, Kanji TSURU, Kunio ISHIKAWA
    2020 Volume 128 Issue 8 Pages 555-559
    Published: August 01, 2020
    Released: August 01, 2020
    JOURNALS FREE ACCESS

    β-tricalcium phosphate (β-TCP) with interconnected pores is an attractive substitute for bone because it shows excellent tissue response and osteoconductivity. An interconnected porous structure is a key factor for fast osteoconductivity, because it facilitates tissue and cell penetration. However, it is challenging to attach interconnected porous structure to β-TCP blocks. In this study, a new, simple, and safe method for fabricating interconnected porous β-TCP was developed, based on an analogous dental glass ionomer cement setting reaction. β-TCP granules were mixed with polyacrylic acid (PAA) by loading; PAA got bound to these granules and got set to form an interconnected porous structure; the sintering process decomposed PAA and yielded the interconnected porous β-TCP structure. Diametral tensile strength and porosity of the fabricated samples were 1.3 ± 0.2 MPa and 57.6 ± 1.1%, respectively. These values of samples were enough value for applying bone substitute. β-TCP with interconnected pores synthesized using the novel method described, herein, would be a suitable bone substitute in clinical settings.

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  • Yuta SHUSEKI, Fumihiro MIHARA, Atsuo YASUMORI, Yasushi IDEMOTO, Setsuk ...
    2020 Volume 128 Issue 8 Pages 560-564
    Published: August 01, 2020
    Released: August 01, 2020
    JOURNALS FREE ACCESS

    The Fukushima nuclear power plant accident caused an outflow of pollutants. Thus, precautionary measures must be taken by using preventive materials for the deterrence of such accidents. Herein, we aimed to develop inexpensive materials that can remove radioactive elements from an aqueous solution. We found that powders obtained from milling scallop shells, which were discarded in large quantities, removed Sr2+ from aqueous solutions. The Sr2+ removability of the scallop shell powder improved with milling time, indicating the influence of increase in the specific surface area on Sr2+ removability. Despite of the same specific surface area, the scallop shell powder exhibited higher Sr2+ removability than that of the unmilled CaCO3. Differential scanning calorimetry evaluation for the investigation of factors other than the specific surface area revealed that the milled scallop shell powder contained amorphous calcium carbonate. Moreover, we synthesized amorphous calcium carbonate and found that it exhibited 60-times higher Sr2+ removability than that of crystalline calcium carbonate. We concluded that the amorphous structure of calcium carbonate significantly affects the Sr2+ removability from aqueous solutions. It was hypothesized that amorphous calcium carbonate removes Sr2+ by incorporating Sr2+ into the structure during crystallization in an aqueous solution.

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Regular Issue: Notes
  • Shijie FENG, Dongbai SUN, Hongying YU, Wenrui WANG, Lu XIE, Fei ZHAO, ...
    2020 Volume 128 Issue 8 Pages 565-568
    Published: August 01, 2020
    Released: August 01, 2020
    JOURNALS FREE ACCESS

    The La2(Zr0.7Ce0.3)2O7 (LZ7C3) ceramics co-doped with Ca2+ and different transition metal cations (Fe3+, Cr3+) were fabricated by the pressureless-sintering method. The influence of doping on the phase structure, microstructure and infrared emissivity (0.75–2.5, 3–5, 8–14 µm) was investigated. The infrared emissivity of LZ7C3 in the wavelength range 0.75–2.5 and 3–5 µm was significantly enhanced by co-doping, especially with Ca2+ and Cr3+. The infrared emissivity in the wavelength range 0.75–2.5 µm could be improved from 0.069 (LZ7C3) to 0.876 at room temperature, and from 0.463 (LZ7C3) to 0.877 in 3–5 µm at 300 °C, by co-doping with Ca2+ and Cr3+. On the other hand, doping had an insignificant effect on the infrared emissivity of LZ7C3 in the 8–14 µm range at 300 °C due to its high emissivity value (0.962) in the 8–14 µm range.

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  • Kensaku NAKAMURA, Naoya OTANI, Tetsuya KOIKE
    2020 Volume 128 Issue 8 Pages 569-572
    Published: August 01, 2020
    Released: August 01, 2020
    JOURNALS FREE ACCESS

    Our study shows that machine learning technique, Bayesian optimization (BO) can efficiently find high-refractive-index glasses from a large number of candidate compositions using data from the INTERGLAD database. The effect of the parameters (i.e., descriptors) input to the BO algorithm on search performance is described. The results show that elemental-property-based (EPB) descriptors, recently applied in materials science, are more effective than the component-amount-based ones traditionally used in the study of glass. The results suggest that BO with EPB descriptors can accelerate the search for glass compositions with desirable properties.

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  • Koji KURAOKA, Kazumi MIKI
    2020 Volume 128 Issue 8 Pages 573-576
    Published: August 01, 2020
    Released: August 01, 2020
    JOURNALS FREE ACCESS

    Inorganic–organic nanocomposite gas barrier membranes with high content of layered double hydroxide (LDH) using surface modified LDH on plastic film were prepared by cross-linking reaction. The effect of LDH content on the gas barrier properties [oxygen permeation and water vapor transmission rate (WVTR)] of the membrane was investigated. The oxygen permeability coefficient of the nanocomposite layer was small, and about one-tenth of polyvinylidene chloride (PVDC) and WVTR (thickness 25 µm) of the nanocomposite layer was on the same order as PVDC. The pencil hardness (750 g load) of the nanocomposite membrane was higher than that of substrate, polyethylene terephthalate film. The value was HB. The balance between high gas barrier properties and hardness were thought to be due to the well-dispersed inorganic component (LDH) and organic component in the nanocomposite. From the results, it was found that the reported inorganic–organic nanocomposite membranes can be applied to gas barrier membranes.

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