Structural deformation of a magnetocapacitive material SmMnO₃ was studied by X-ray diffraction measurement in a magnetic field. This antiferromagnetic material shows a jump in dielectric constant at 9 K only when a magnetic field of a few tesla is applied. In-field X-ray diffraction measurements clarified that there is no sudden change in structure that involves atomic displacement within the c-plane in Pbnm notation, while the antiferromagnetic phase transition at 60 K gives rise to a noticeable rotation of the MnO₆ octahedra. This rotation occurs to maximize the energy gain through the exchange interaction.

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Lead free positive temperature coefficient of resistivity (PTCR) thermistors with switching temperature T_S of 155°C were synthesized from 0.95BaTiO₃–0.05(Bi_1/2K_1/2)TiO₃ solid solution for high temperature applications, utilizing the conventional ceramic fabrication technique, which involved sintering ceramics in N₂ flow followed by air annealing. Addition of sintering aid AST (Al₂O₃:SiO₂:TiO₂ with 4:9:3 molar ratio) and Mn improved the bulk PTCR response. Impedance spectroscopy analysis confirmed the bulk T_S and revealed a third ferroelectric resistance-capacitance (RC) element along with a semiconducting grain and PTCR active ferroelectric grain boundary. The investigation of local electrical activity adopting hot-stage conductive mode microscopy revealed the existence of type-I grain boundary-electron beam induced current (GB-EBIC) contrast pertinent to the presence of negatively charged interfaces neighbored with compensating positive space-charge layers typical of double Schottky barrier within the Pb free PTCR system.

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Ferroelectric materials with excellent performance without containing lead has been desired for saving human body from a harmful element, lead. The authors have reported BaTiO₃ (BTO) thin films with enhanced ferroelectricity by stress engineering by thermal stress assisted by LaNiO₃ (LNO) bottom electrodes. In the present study, we investigate the local stress state of the BTO and LNO films using TEM techniques. TEM observation reveals that the LNO film is porous structure whereas the BTO film is dense. Electron diffraction and dark field images of the films also reveal that the BTO and LNO films oriented along [001] and [100] directions perpendicular to the film plane, respectively. Another effect on the stressed BTO films, increased Curie temperature owing to the stabilized tetragonal phase, is also reported.

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To study the effect of step edges on the growth of Pt thin films on oxide substrates, Pt films were grown on SrTiO₃(100), rutile TiO₂(100), and Al₂O₃(11–20) stepped surfaces at 673 and 973 K by pulsed laser deposition. No clear effect due to the step edges on the film growth was found on the SrTiO₃ at 673 K. However, the Pt grains were larger in size at the step edges than on the terraces at 973 K. The estimated length of the Pt surface diffusion was longer than the average terrace width at 973 K and shorter at 673 K. Similar growth behavior was also observed on the TiO₂ at 973 K, while there was no clear effect caused by the step edges in the case of the Al₂O₃. The Pt diffusion length was estimated to be longer than the terrace width on the TiO₂ and shorter on the Al₂O₃. The effect of the step edges can therefore be understood by considering the Pt surface diffusion.

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Ultrafast time-resolved Bragg coherent X-ray diffraction (CXD) has been performed to investigate lattice dynamics in a thin crystal layer with a nanoscale thickness by using a SASE (Self-Amplified Spontaneous Emission)–XFEL (X-ray Free Electron Laser) facility, SACLA. Single-shot Bragg coherent diffraction patterns of a 100 nm-thick silicon crystal were measured in the asymmetric configuration with a grazing exit using an area detector. The measured coherent diffraction patterns showed fringes extending in the surface normal direction. By using an optical femtosecond laser-pump and the XFEL-probe, a transient broadening of coherent diffraction pattern profile was observed at a delay time of around a few tens of picosecond, indicating transient crystal lattice fluctuation induced by the optical laser. A perspective application of the time-resolved Bragg CXD method to investigate small sized grains composing ceramic materials is discussed.

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A new synchrotron X-ray diffractometer with a one-dimensional X-ray detector has been successfully developed for the purpose of high angular resolution, high efficiency and full automatic powder X-ray diffraction experiments. Sample-to-detector distance is designed to be 955 mm. This long distance enables us to obtain high angular resolution powder diffraction data. The one-dimensional detector can observe 3.84 degrees in 2θ per one exposure, thus multiple exposures at every 2θ angle are required to collect a whole powder diffraction pattern. The minimum step size of 2θ is approximately 0.003 degrees. A full automatic data-collection system is achieved with a newly developed diffractometer control program that covers the whole system; a sample exchanger, a sample position adjustment, diffractometer axes and data collection. Diffraction peak profile and angular resolution are comparable to that of the imaging plate Debye–Scherrer camera with the same sample-to-detector distance. Diffraction data of a standard sample (NIST-CeO₂) obtained by this system was analyzed properly using Rietveld method.

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Dynamics of coherent G-mode and D-mode phonons in Ar⁺-ion implanted graphite has been investigated using transient reflectivity measurement. With an increase in the Ar⁺-ion dose, coherent D-mode phonon appears at which the dephasing rate of the coherent G-mode phonon begins to increase. The increase in the amplitude of the coherent D-mode phonon and those in dephasing rates of the coherent D-mode and G-mode phonons indicate effective carrier-defect scatterings in the defective graphite. The dephasing rate of the D-mode is larger than that of the G-mode, indicating an existence of an additional dephasing process for the D-mode. We attribute it to the broad spectral distribution of the D-mode phonon, which is understood as a coherent excitation of large wavevector phonons with different wavevectors through inter-Dirac-cone scattering. The frequency chirping of the D-mode and its defect density dependence are also discussed based on this scattering mechanism.

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Amorphous In–Ga–Zn–O (a-IGZO) thin-film transistors (TFTs) annealed in ozone at 250°C exhibited a good subthreshold swing (S) of 123 mV/decade and a saturation mobility (μ_sat) of ~10 cm²/Vs, but a bit large threshold voltage (V_th) of 11.6 V. Further oxygen annealing at 200°C resulted in high apparent μ_sat of ~30 cm²/Vs and deteriorated characteristics such as a large S value and large hysteresis. The high apparent μ_sat values were attributed to the electrical discharge between the gate and source electrodes. Reasonably actual μ_sat values ~10 cm²/Vs were obtained using the actual capacitance calculated from the discharge characteristics.

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A cosolvent-free sol–gel method to synthesize monolithic silica glasses containing both of rare-earth and aluminum ions has been studied. Fracture during drying and bloating during sintering are significantly suppressed by forming macroporous wet gels via macroscopic phase separation in parallel with gelation. The resultant rare-earth and aluminum codoped silica glasses exhibit good visible transparency, suggesting an improvement of dispersion of rare-earth ions in these glasses. The aluminum codoping increases the photoluminescence efficiency in glasses doped with Nd³⁺ ions.

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Cinnamate/layered double hydroxide (LDH) composites were prepared by a reconstruction method using sodium cinnamate solution. The cinnamate solution of 100 mM was the most remarkable condition to obtain high cinnamate content of the cinnamate/LDH composite. The composite included about 30 mass % of cinnamate was prepared using the LDH with Mg/Al = 2. In this composite, the new interlayer observed in XRD at 2θ = 4.5° formed a bilayer configuration of cinnamate. This composite showed excellent UV absorbability in UV-B region. Although the interlayer cinnamate changed into a dimer structure after UV radiation, the original UV absorbability was maintained in the composite.

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Solid-state reaction between BaCO₃ and ZrO₂ is the simplest method to prepare BaZrO₃, which is an important refractory structural material with a very high melting point and a low chemical reactivity. However, since the solid-state formation of the BaZrO₃ phase requires high calcination temperature, this method typically produces larger particles unsuitable for the sintering process than the solution methods. In this study, we investigated the reaction behavior between very fine ZrO₂ (70 nm) and coarse BaCO₃ (1.5–5.7 µm) and described the water vapor-assisted solid-state synthesis of BaZrO₃. Nanocrystalline BaZrO₃ powder (~80 nm) was obtained by solid-state reaction at 1050°C in air. The BaZrO₃ formation was accelerated by water vapor-assisted reaction. The apparent activation energy for the formation reaction was calculated to be 323 ± 21 kJ/mol and 263 ± 46 kJ/mol in air and humid air with H₂O of 0.5 atm, respectively. In the 1 atm water vapor atmosphere, almost single-phase BaZrO₃ was obtained by calcination at 750°C.

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We produced porous ceramics for gas separation using membrane formation of Nd₂Fe₁₄B powders on alumina (Al₂O₃) support. The average pore size and porosity of the alumina support were, respectively about 67 mm and 34–40%. Selectivity of this support was about 1.07, which well agreed with Knudsen diffusion. The coated Nd₂Fe₁₄B membrane thickness was about 166 µm. The sample selectivity after membrane formation was 1.07. Gas selectivity properties were not developed. When magnetized on the same sample, gas selectivity appeared at low differential pressure at gas permeation. Samples with a lower gas flow rate of the alumina support exhibited higher selectivity. The maximum was 1.22.

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Weakly agglomerated nano-crystalline Ho₂O₃ and Sc₂O₃ stabilized ZrO₂ (HoScSZ) powders are prepared by the hydrothermal method. Dense HoScSZ ceramic pellets are fabricated by isostatically pressing the powders then sintering at 1350°C for 2 h. All the HoScSZ samples are cubic phase verified by X-ray diffraction. 7 mol % Sc₂O₃ + 1 mol % Ho₂O₃ stabilized zirconia (7Sc1HoSZ) is verified by impedance spectroscopy possessing the higher conductivity than that of 8 mol % Sc₂O₃ stabilized zirconia (8ScSZ). Space charge potential and specific grain boundary conductivity are calculated and fitted under the circumstance that the grain boundary is free of any amorphous phase which is verified by high resolution transmission electron microscopy. With the increase of the doping content of Ho₂O₃, the specific grain boundary conductivity and space charge potential decrease, while oxygen vacancy concentration increases.

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