Platinum catalyst loaded tungsten oxide (Pt/WO₃) is a promising candidate as a hydrogen gas sensor material, which can detect it through optical and electrical sensing. The sensor, which can detect the hydrogen gas stably in various environments, is strongly demanded. In this study, we prepared the Pt/WO₃ thin film by the sol–gel method and evaluate the dependence of the hydrogen gas sensing property on measuring temperature and humidity. Hydrogen gas sensing property of Pt/WO₃ thin film was evaluated by measuring the electrical conductivity with humid (0–100% of relative humidity) hydrogen gas exposure at various temperatures. The sensing property was declined in humid atmospheres because the water molecule adsorbing on the film surface disturbed the catalytic reaction between hydrogen and Pt surface. In addition, the catalytic combustion of hydrogen molecule on Pt was also disturbed by the adsorbed water. However, the heating at 60°C can remove the effect of water molecule and the film can detect hydrogen gas stably. From these results, it was considered that the degradation of sensor response in humid atmosphere was mainly dominated by adsorbing water on Pt catalyst surface.

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Influence of oxygen vacancy (V_O^••) distribution on the polarization properties of SrRuO₃(SRO)/BiFeO₃(BFO)/SRO capacitors was investigated. Our thin-film experiments and density function theory (DFT) calculations reveal that a strong attractive interaction between V_O^•• and the bottom BFO/SRO interface gives rise to an V_O^••-rich defective layer for as-deposited capacitors. The distribution with the V_O^••-rich layer is gradually broken by an electrical training and finally becomes symmetric, leading to a polarization-hysteresis change from a markedly rounded to a typical ferroelectric loop. This study demonstrates that defect engineering utilizing V_O^•• is an effective approach to control the polarization-related properties of BFO in capacitor form.

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Ba(Zr_x,Ti_1−x)O₃ nanocubes (BZT_x NCs) were synthesized by hydrothermal reaction with titanium and zirconium aqueous compounds and surfactants. The nanocubes were assembled on the substrates by dropping-drying method. The microstructures of the nanocube were evaluated by field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The ordered assemblies of the NCs were yielded on the substrate when Zr contents were below 0.2. BZT_0.2 NCs had narrow size distribution about 20 nm observed by FE-SEM and TEM. On the other hand, BZT_0.5 and BaZrO₃ NCs were attached each other and they formed large cube above 100 nm. Perovskite phase was confirmed in all BZT_x NCs by X-ray diffraction. Lattice constant of BZT_x NCs increased linearly with increasing Zr contents. The composition of BZT_0.2 NCs were calculated by X-ray photoelectron spectroscopy. These results suggest that the ratio of Ba:Zr:Ti is nearly equal to the nominal ratio. Crystallographic phase of BaTiO₃ and BZT_0.2 NCs was characterized by Raman spectroscopy under various measurement temperatures.

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The diffusion of silver, Ag, as the electrode material in (Bi_1/2Na_1/2)TiO₃ (BNT) ceramic was studied by means of a secondary ion mass spectrometry (SIMS). The Ag diffusion along the grain boundary was confirmed. The diffusion coefficient of Ag in BNT is almost equal to that of Pb-based ceramics. The intergranular fracture is considered to be associated with the grain boundary diffusion of Ag. The apparent diffusion coefficients of Ag were obtained using SEM images of cross sections after Ag diffusion. The temperature dependence of Ag apparent diffusion in BNT ceramics was described by 2.3 × 10⁻³ cm²/s of pre-exponential factor and 132.2 kJ/mol of the activation energy in the temperature range of 700–900°C as diffusion treatment.

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Thin films of the BaTiO₃–Bi(Mg_1/2Ti_1/2)O₃ (BT–BMT) solid-solution system with preferential crystal orientation of (100) and (111) plane were fabricated on (100)SrRuO₃//(100)SrTiO₃ and (111)SrRuO₃//(111)SrTiO₃ substrates by CSD technique. Enhanced dielectric permittivity (ε_r) of approximately 800 was confirmed for the (111)-oriented BT–BMT film at room temperature, which is significantly larger than those of (100)- or randomly-oriented films. The BT–BMT films exhibited relatively stable temperature coefficient of capacitance (TCC) independent of their crystal orientation, that allows enhanced ε_r up to 400°C without drastic change of the capacitance. These properties can be favorable for the application of dielectric capacitors in high-temperature electronics.

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Nitride thin-film materials are deposited on resin substrates for application as flexible thin-film temperature sensors. Highly crystalline wurtzite (Al,Ti)N films deposited on polyimide substrates offer both negative temperature coefficient properties and flexibility. Thermistor constants (B values) are analyzed by measuring the temperature dependence of the electrical resistivity, Hall resistivity, and thermoelectric power. The B value is found to largely depend on the nitrogen content rather than on the titanium content in (Al,Ti)N, which suggests that electrical conduction through nitrogen atoms plays an important role in thermistor properties. The difference in electrical conduction mechanism between nitrides and oxides is also discussed on the basis of the analysis.

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In this study, in situ time-resolved dispersive X-ray absorption fine structure (DXAFS) analysis of BaTiO₃–LiCoO₂ (BT–LC) composites for lithium ion batteries was performed to characterize the cobalt ion valence shift between oxidized and reduced states of driven cells, in an attempt to better understand the contribution of ferroelectric solid electrolyte interfaces (SEIs) to charge–discharge rates. Two types of artificial SEIs, ferroelectric BT and paraelectric Al₂O₃, were compared. The magnitude of the shift in the X-ray absorption energy at the peak of the white line, E₁, during charging and discharging at a 10 C rate, increased in the order of bare LC (0.264 eV) < Al₂O₃ 1 mol % (0.497 eV) < BT 1 mol % (1.15 eV); the corresponding discharge capacities of the laminated cells at 10 C were as follows: bare LC (11.6 mAh/g) < Al₂O₃ (41.8 mAh/g) < BT (95.1 mAh/g). The increase in E₁, i.e., the oxidation of Co during charging, intensified under a higher applied potential for the BT-decorated composite compared with that of the Al₂O₃-coated specimen. The stronger oxidation of Co for BT–LC under application of a large electric field was attributed to the strengthened polarization due to the larger permittivity of BT.

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(Sr_0.7Bi_0.2)TiO₃ ceramics were fabricated by a solid state reaction, and a wideband dielectric spectrum was measured for understanding the microscopic polarization mechanism of (Sr_0.7Bi_0.2)TiO₃ ceramics. It was revealed that the dielectric permittivity of (Sr_0.7Bi_0.2)TiO₃ ceramics at 25°C was determined by dipole polarization as well as ionic polarization, whereas the permittivity of SrTiO₃ is mainly determined only by ionic polarization. The temperature dependence of permittivity suggested that (Sr_0.7Bi_0.2)TiO₃ ceramics belongs to ferroelectric relaxor, in which off-center Bi³⁺ ions contribute to the formation of polar nanoregions (PNRs). The origin of the dipole polarization is considered the dipole fluctuations of PNRs. On the other hand, the ionic polarization of (Sr_0.7Bi_0.2)TiO₃ ceramics was suppressed by an influence of Sr-site vacancy, compared to that of SrTiO₃. High permittivity of (Sr_0.7Bi_0.2)TiO₃ ceramics is mainly due to the dipole polarization associated with dipole fluctuation of PNRs.

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Al-incorporated ZnO films with various Al concentrations were prepared using pulsed laser deposition on the (11-20) face of sapphire substrates, and their gas sensing properties were evaluated. The use of c-axis-oriented epitaxial films with the same thickness suppressed the influence of the surface-to-volume ratio and surface atomic arrangements on the sensing properties, clarifying the role of Al doping in the improvement of ZnO gas sensors. The results of ethanol gas sensing measurements indicated that Al doping significantly improved the sensing response and response time of the ZnO gas sensors. The formation of Al-related impurity phases and/or non-equilibrium defects induced by Al doping improved the sensing performance. On the other hand, changes in the grain size did not significantly affect the sensing response.

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Layered hydroxide zinc carbonate (LHZC) films were fabricated on glass substrates through a chemical bath deposition method using aqueous solutions. The films had morphologies where sheet-like LHZA particles were accumulated more or less vertically to the substrate surface. Changes in the concentration of a zinc source and the increasing rate of pH had a remarkable effect on the b-axis orientation and the film density of the LHZC films. The morphologies of the LHZC films were maintained after their conversion to ZnO by thermal treatments. The increase in the film density resulted in the improvement of the open-circuit voltage and the fill factor of dye-sensitized solar cells using N719-loaded ZnO films as photoanodes. The light-to-electricity conversion efficiency of 3.49% was obtained in the DSSC using the present ZnO film.

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We investigated the phase formation and the conductive properties of the Al-free Li_7−xLa₃Zr_2−xTa_xO₁₂ (0 ≤ x ≤ 0.6) samples. The X-ray diffraction patterns of the Li₇La₃Zr₂O₁₂ (x = 0) and Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (x = 0.6) samples were assigned to be single phases of tetragonal (space group: I4₁/acd) and cubic (space group: Ia-3d) structures, respectively. On the other hand, the intermediate compositional samples of Li_7−xLa₃Zr_2−xTa_xO₁₂ (0.2 ≤ x ≤ 0.5) showed a coexistence of both the tetragonal and cubic phases. To investigate the conductive property of the prepared samples, the Li-ion conductivity was measured in a temperature range from 253 to 313 K by AC impedance method. All of the Al-free Li_7−xLa₃Zr_2−xTa_xO₁₂ (0 ≤ x ≤ 0.6) samples exhibited relatively high conductivity of ∼10⁻⁴ S cm⁻¹ at room temperature, and the Li_6.5La₃Zr_1.5Ta_0.5O₁₂ (x = 0.5) sample showed the highest Li-ion conductivity of 8.4 × 10⁻⁴ S cm⁻¹ at room temperature. In order to clarify the relationship between the Li-ion conductivity and the Li-ion arrangement, the crystal structure analysis of Li_7−xLa₃Zr_2−xTa_xO₁₂ (0 ≤ x ≤ 0.6) was performed by Rietveld analysis using powder X-ray diffraction data. The Li(2) atom at 96h site was gradually shifted together with increasing Ta-content from x = 0.2 to 0.5 resulting the shorter Li–Li distance in the loop structure of the cubic garnet-type framework structure.

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This would be the first report that transmission line pulse (TLP) analysis for stability against electrostatic discharge (ESD) of Cu-MLCVs reveals the effect of ZnO grain resistivity under ESD zapping. The influence has been evident from results over a wide range of V–I characteristics provided by TLP measurement. ESD stability is found to be closely related to variations of ZnO grain resistivity, greatly depending on oxygen partial pressure (P_O2) during sintering. The lowering of ZnO resistance leads to high stability against ESD. Thus, the stability is demonstrated to be drastically improved with decreasing ohmic resistance down to the lowest levels by sintering below P_O2 of 1.6 × 10⁻⁹ MPa. Then, influence of Cu diffusion on their properties of MLCVs was investigated in bulk-disks of SrCoO₃ doped-ZnO with various CuO additions. The enhancement of ZnO grain resistivity is caused by the slight diffusion of Cu⁺ during the sintering in a relatively weak reducing P_O2 above 2.2 × 10⁻⁹ MPa, resulting in low ESD stability. However, ZnO grain resistivity is not influenced by Cu diffusion below 0.005 mol % as CuO, thus Cu-MLCVs containing below the affected level have been considered bringing high ESD performance. It was confirmed experimentally that sintering of Cu-MLCVs in the optimum reducing atmosphere provides high ESD stability and significant suppression (about 1100 to 150 V) for ESD zapping at 8 kV under IEC61000-4-2. Cu-MLCVs obtained are able to have high protection performance as well as ESD stability at the same level as a device in practical use. Lowering of ZnO resistivity by a decrease of Cu diffusion is believed to give benefits to overall performance of Cu-MLCVs.

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Hf_0.5Zr_0.5O₂ (HZO) thin films with orthorhombic phase Pca2₁ are novel ferroelectric materials. We have attempted the epitaxial growth of HZO thin films using solid-state epitaxy with ion-beam sputtering followed by rapid thermal annealing. X-ray diffraction (XRD) profiles of HZO thin films on SiO₂ glass substrates showed {111}-oriented monoclinic and orthorhombic phases. On the other hand, XRD profiles of HZO on yttria stabilized zirconia (YSZ) (100) substrates indicated the shoulder peak on the strong tail of 200 peak of YSZ substrates in the lower 2θ side. Structural analyses of the HZO thin films have conducted to identify constituent phases, the local orientation, and the nanostructure of HZO thin films using aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and the related STEM-EDS analysis. In this paper, we have described the orthorhombic (Pca2₁) and monoclinic (P2₁/c) phases coexisted based on multislice image simulation and diffractogram analysis of the local regions in HZO thin films. The principal phase in the HZO/YSZ epitaxial thin films is the orthorhombic phase. Each phase was epitaxially grown on the YSZ substrate with a domain structure of the order of 10 nm in size. The orthorhombic phase has formed in the HZO/SiO₂ glass thin films, which indicates that the stability of the orthorhombic phase is ascribed to not only pseudomorphic or lattice mismatch effects of the substrate but also doping effects and thermal mismatch between the film and the substrate. The mosaicity of thin film is high because of lattice deformation with coexisting monoclinic phase and a damaged region between thin film and substrate caused by sputtered particles with high energy. Orthorhombic single-phase thin films with higher quality can be obtained by preparing ultrathin HZO epitaxial thin films under lower Ar-ion beam energy in the sputtering process and the higher crystallization temperature in the post-annealing process.

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Ru thin films were deposited by pulsed metal organic chemical vapor deposition on SiO₂ (native oxide)/(001)Si, HfSiON/SiON/(001)Si, and HfO₂/SiON/(001)Si substrates at 200, 210, and 230°C from bis(2,4-dimethylpentadienyl)ruthenium [Ru(DMPD)₂]–O₂ system. Incubation time before starting the film deposition strongly depended on the deposition temperature. Atomic force microscopy (AFM) revealed that average surface roughness, Ra, of the Ru films deposited on HfO₂/SiON/(001)Si substrates strongly depended on the deposition temperature even though those films deposited on SiO₂ (native oxide)/(001)Si substrates and HfSiON/SiON/(001)Si substrates showed small dependency on deposition temperature. In addition, it was obvious that the grain size of Ru films deposited on HfO₂/SiON/(001)Si substrate was larger than those deposited on SiO₂ (native oxide)/(001)Si substrates. Minimum film thickness to obtain continuous Ru film was almost independent on the kinds of substrates and deposition temperature range from 200 to 230°C. These results clearly show the effect of kinds of substrates and deposition temperature on flat and continuous Ru film deposition.

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This paper describes growth behaviors of chemically-ordered regions (CORs) in Pb(Mg_1/3Nb_2/3)O₃ (PMN) epitaxial thin films. The films are crystalized at 650°C, which corresponds to about half of the crystallization temperature of bulk crystals. We obtained PMN epitaxial thin films with high crystallinity by using a metallo-organic decomposition (MOD) process. According to our atomic-resolution analysis using HAADF-STEM images, it is shown that CORs in PMN epitaxial thin films grow by nucleation of small clusters whose sizes are 1 to 2 nm on each side of habit plane, {100} and {110}. In addition, post-annealing process at 700 or 800°C causes growth of CORs. The growth mechanism of CORs is not by the expansion of each cluster but by the nucleation of new clusters. After post-annealing at high temperatures, CORs join with each other on their habit plane and made a network along ⟨100⟩, ⟨110⟩ and ⟨112⟩ direction.

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We report the red-emitting mechanoluminescence (ML) materials based on the piezoelectric semiconductors MZnOS:Mn²⁺ (M = Ca, Ba) synthesized by solid-state reaction. Both of the CaZnOS:Mn²⁺ and BaZnOS:Mn²⁺ show red light emission upon the compressive load, and the CaZnOS:Mn²⁺ emits a more intense red ML light at the same condition. We propose it should be considered to the polar non-centrosymmetric crystal structure of CaZnOS.

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Micrometer-sized single crystals of spinel-type LiCoMnO₄ were synthesized by heating a mixture of LiOH·H₂O, CoCl₂, and MnCl₂ with a molar ratio of Li:Co:Mn = 1.5:1:1 at 750°C. X-ray diffraction (XRD) pattern and scanning electron microscopic (SEM) image showed that LiCoMnO₄ has cubic spinel structure with well-formed octahedral crystal shapes. The size of the obtained LiCoMnO₄ single crystal particles was about 1–3 µm. Rietveld analysis using power XRD data confirmed the cubic spinel-type structure with space group Fd-3m, and the lattice parameter of a = 8.05812(14) Å. The tetrahedral 8a site was occupied by both Li and Co atoms with the occupancy values of Li/Co = 0.958/0.042. Electrochemical measurement exhibited the reversible Li-ion extraction and insertion reactions at high potentials. The discharge profile with the discharge capacity of 107 mAh g⁻¹ showed three voltage plateaus at 5.1, 4.9, and 3.9 V; the former two corresponded to the redox reaction of Co³⁺/Co⁴⁺ and the latter was to the redox reaction of Mn³⁺/Mn⁴⁺, respectively.

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We have successfully prepared H₂Ti₁₂O₂₅ by soft chemical synthetic technique using Na₂Ti₃O₇ as a precursor material. The crystal system is the monoclinic system, space group C2/m, and its lattice parameters were refined to be a = 12.4485(2) Å, b = 3.74414(3) Å, c = 19.9523(5) Å and β = 95.244(2)° by electron diffraction pattern and powder X-ray diffraction pattern. The crystal structure of H₂Ti₁₂O₂₅ and lithium-ion inserted H₂Ti₁₂O₂₅ were estimated by Monte Carlo method for the first time. As a result, the formula of the lithium-ion inserted state was Li₁₀H₂Ti₁₂O₂₅. From these results, theoretical capacity was estimated to be 274.6 mAh/g. The total protonic conductivities in H₂Ti₁₂O₂₅ was estimated to be σ_total = 8.71 × 10⁻⁹ S cm⁻¹ at room temperature from the results of AC-impedance. The estimated band gap for H₂Ti₁₂O₂₅ is about 3.34 eV, the value of which is very similar to those for Na₂Ti₆O₁₃ and Li₂Ti₆O₁₃.

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Zinc-doped Tin-dioxide thin (SnO₂) films were synthesized on c-alumina substrates by radio-frequency (rf) sputtering. To fabricate zinc-doped SnO₂ thin films with different concentrations of zinc, an insulating zinc-doped SnO₂ target was placed on a conductive non-doped target. Thin films were then deposited at different flow rates of argon gas. Zinc concentration in the deposited SnO₂ thin films increased with increasing flow rate of argon gas. Moreover, the SnO₂ thin film with a zinc concentration of 2.2 × 10¹⁹/cm³ showed the highest gas-sensor response. It is concluded that this rf-sputtering growth method is a useful tool for identifying suitable materials compositions for creating gas sensor with response for hydrogen and ethanol.

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The structural change of Na₂O·5SiO₂ and Na₂O·3SiO₂ glasses by melting were analyzed. From their droplet specimens that were levitated by N₂ gas flow and melted by CO₂ laser irradiation, the X-ray diffraction spectra were successfully obtained, using 61.41 keV high energy X-ray from synchrotron radiation. The obtained spectra were corrected, normalized, and then Fourier-transformed to radial distribution functions (RDFs). It was found that the Si–O, Na–O, O–O, and Si–Si peaks in the RDFs got broadened and shifted to longer distance compared with the solid glasses, while no significant difference was found between the RDFs of the melts at 900 and 1200°C. In the classical molecular dynamics simulations using Born–Mayer–Huggins type two-body potential with optimized parameters, the trends of RDF change by melting described above were well reproduced. The simulated structural models indicated that the distortion of SiO₄ tetrahedra, increase of Na–O distance, and cleavage of Si–O and Na–O bonds are occurring in the melts.

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Epitaxial CeO₂/Ce_1−xZr_xO₂/Y_0.15Zr_0.85O_1.93 (YSZ) buffer layers were fabricated on a Si(100) substrate by pulsed laser deposition, and its crystallinity and surface roughness were analyzed. When Ce_1−xZr_xO₂ (x = 0–0.6) films were directly deposited on the Si(100) substrate, the films had a (111) or (111)-preferred orientation. In contrast, (100)-oriented epitaxial films of the Ce_1−xZr_xO₂ (x = 0–0.6) were obtained by introducing a 2.5-nm-thick YSZ buffer layer between Ce_1−xZr_xO₂ and Si. Lattice parameters and surface roughness of the Ce_1−xZr_xO₂ layers on the YSZ-buffered Si(100) decreased from 0.542 to 0.525 nm (in-plane) and 0.47 to 0.12 nm, respectively, as the increase of x from 0 to 0.6. After that, an epitaxial CeO₂/Ce_0.4Zr_0.6O₂/YSZ buffer layer was fabricated on the Si substrate. Differences in lattice parameters between CeO₂ and Ce_0.4Zr_0.6O₂ and also between Ce_0.4Zr_0.6O₂ and YSZ became about half of that between CeO₂ and YSZ. As a result, surface roughness of the CeO₂ layer on top of the Ce_0.4Zr_0.6O₂/YSZ/Si and full width at half maximum of the rocking curve of the CeO₂ (004) reflection became 0.18 nm and 0.89 degrees, respectively, which were smaller than those of CeO₂ layers deposited directly on YSZ/Si.

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Polycrystalline mullite fibers (3Al₂O₃·2SiO₂) using aluminum powders, aluminum chloride and silica sol as raw materials and water as solvent were prepared by precursor method to reduce its production costs. Spinnable mechanism of the sols and the stretching and bending modes of vibration of chemical bonds were discussed. The spinnability influence factors, including reaction times, reaction temperature, the proportion of Al and AlCl₃, the rotate speed, the rotary steam temperature were investigated. When the range of Al/AlCl₃ molar radio was from 3.4 to 3.5, reaction time 5.5 h, reaction temperature 80°C, optimal spinning precursor sols were obtained. Then at 80°C the spinning sols were spun using a laboratory miniature spinning apparatus in the rotate speed of 500 rpm. The drawn mullite precursor gels were dried at 60°C for 24 h. The dried samples were sintered with a slow heating rate of about 3°C/min up to 1300°C for 2 h in air atmosphere and the polycrystalline mullite fibers were obtained. The microstructure, thermal behaviors, chemical bends, and phase evolution of mullite fibers were characterized with thermogravimetric analysis (TG), differential thermal analysis (DTA), X-ray diffractometry (XRD), fourier transform infrared spectroscopy (FT-IR), and scanning electron microscope (SEM). The refractoriness of the polycrystalline mullite fibers was at least 1600°C.

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The unipolar fatigue behavior of undoped Li_0.06Na_0.52K_0.42NbO₃ (LNKN6-a) and the same compound with additives (LNKN6-b) were observed. Unipolar cycling was performed between room temperature and 150°C under a high unipolar electric field of 4 kV/mm. LNKN6-a fatigued under crack formation throughout the examined temperature range. The switchable polarization 2P_r of LNKN6-a decreased for 20% (=2 µC/cm²) at 150°C. In contrast, mechanical degradation was not observed in LNKN6-b. The switchable polarization 2P_r of LNKN6-b decreased for 15% (=3.2 µC/cm²) at 150°C. It should be noted that at 50°C, fatigue-free behavior was observed for LNKN6-b over at least 10⁶ cycles. The influence of phase transition on this fatigue-free behavior was discussed.

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The productions of calcium hydroxyapatite (Hap) and Ti(IV)-doped Hap (TiHap) particles were examined by forced hydrolysis reaction of Ca(OH)₂-pyrophosphate (pp: P₂O₇⁴⁻) and Ca(OH)₂-pp-TiCl₄ mixed solutions under 100 and 140°C, respectively, and precipitated particles were characterized by various physicochemical techniques. The degree of hydrolysis of pp ions was remarkably improved and the yields of the precipitates by using the pp ions was increased rather than the tpp one. No particles were produced at higher concentration of pp ions. On the other hand, ellipsoidal aggregated and rod-like particles were produced at other concentration domains. The Hap particles produced were ellipsoidal secondary particles with ca. 210–240 nm in the particle length which were composed by aggregation of small primary single crystal particles with ca. 20–50 nm in length. The TiHap particles facilitated at atomic ratio of Ti/(Ca+Ti) [X_Ti] ≦ 0.20 were ellipsoidal secondary particles with ca. 240–380 nm in length composing by aggregation of small primary particles with ca. 30–100 nm in length, while they were changed to very fine particles with ca. 5–10 nm in diameter along with small amounts of large rod-like particles at X_Ti = 0.3. The highly crystallized pure TiHap particles were produced at X_Ti ≦ 0.15, while the Hap structure was almost disappear at X_Ti = 0.2. All the TiHap particles produced at X_Ti ≤ 0.2 were phosphorus deficient. The diffuse reflectance UV spectra of TiHap particles revealed that these particles have a UV absorption property, especially fabricated at X_Ti = 0.05. The highly crystallized TiHap particles (0.05 ≦ X_Ti ≦ 0.15) had also large specific surface area.

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First-principles approaches on reproduction of negative and anisotropic thermal expansion of ceramics were examined. We have tested quasi-harmonic free-energy calculation and molecular dynamics (MD) simulation including lattice change based on the density functional theory. For intuitive understanding, a classical force-field MD was also applied. As a test case, we have chosen cordierite, which is particularly important for recent application for electronic precision components, catalytic converter for automobile exhaust gas, and is known to show negative and anisotropic thermal expansion at a certain region of temperatures. Quasi-harmonic free-energy approach showed appearance of negative expansion of cordierite in certain temperatures, while the anisotropy was not reproduced. We conclude this may be due to lack of anisotropic lattice change throughout the optimization of the unit cell and internal coordinates under hydrostatic pressures at 0 K. On the other hand, MD simulation allowing lattice change showed anisotropy of a-, b-axes and c-axis of cordierite while the negative expansion region in temperature was not found, which may be due to limitation of available size of unit cell. Furthermore, by performing classical force-field MD, we found that local chemical-bond nature is a key in understanding the behavior of the cordierite under finite temperatures. From current simulated results, we propose necessity of intensive works to compare theoretical work with future accessible experiments using single-crystal samples.

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For powder layer process of additive manufacturing, alumina granule containing methylcellulose as organic binder was used to form a firm powder layer by spraying water to the granule, and the powder layers were stacked to obtain a green body. Good shape retention with bonded alumina granules was confirmed in the green body. Debinding and post-sintering of the green body were conducted, resulting in an alumina sintered body without visible gap or interface between the stacked layers.

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Apatite-coated silicon wafers are expected to be utilized for novel biosensors or implants. However, the mechanism and optimum conditions for the formation of an apatite layer on silicon wafer surfaces are unclear. Herein, we examined the effect of pretreating silicon wafers with titanium sputtering and weak alkali aqueous solutions before immersing them in a simulated body fluid (SBF). A week after immersion, silicon wafer surfaces coated with thin titanium layers were covered by hemispherical apatite particles that were produced in a heterogeneous nucleation reaction, whereas untreated silicon wafer surfaces were covered by spherical particles that were produced in a homogeneous reaction. Pretreatment of titanium-coated silicon wafers with 0.1 M NaOH aqueous solution assured heterogeneous apatite formation. Both titanium-coated and untreated silicon wafers were fully covered by the apatite layer after soaking in the SBF for 2–3 weeks. These findings show that pretreatment of silicon wafers with titanium sputtering and weak alkali aqueous solution is effective for obtaining apatite-coated silicon wafers.

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