A brief review on the field of Solid State Ionics, including the diffusion pathway of mobile ions, crystal structure and materials, is presented. In the fluorite-structured ionic conductors such as ceria solid solution Ce_0.93Y_0.07O_1.96, bismuth oxide solid solution δ-Bi_1.4Yb_0.6O₃ and copper iodide CuI, a similar curved diffusion pathway along the <100> directions is observed. In the ionic and mixed conductors with the cubic ABO₃ perovskite-type structure such as lanthanum gallate and lanthanum cobaltite solid solutions, the mobile ions diffuse along a curved line keeping the interatomic distance between the B cation and O^2- anion to some degree. The structure and diffusion path of double-perovskite-type La_0.64Ti_0.92Nb_0.08O_2.99, K₂NiF₄-type (Pr_0.9La_0.1)₂(Ni_0.74Cu_0.21Ga_0.05)O_4+δ , and apatite-type La_9.69(Si_5.70Mg_0.30)O_26.24 are described. The diffusion paths of Li⁺ ions in La_0.62Li_0.16TiO₃ and Li_0.6FePO₄ are two- and one-dimensional, respectively.

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Size controlled hydroxyapatite powders with nanometer sizes were directly prepared by high temperature flame spray pyrolysis. Nanosized hydroxyapatite powders were formed from the evaporated vapors by chemical vapor deposition process. The composition ratio of calcium and phosphorous components was 1.67. The mean size of the hydroxyapatite powders increased from 21 to 81 nm when the concentration of spray solution was changed from 0.05 to 2 mol/L. Sintering of the nanosized hydroxyapatite powders occurred at a temperature of 1000°C, and grain growth increased with increasing the sintering temperatures. The mean grain sizes of the pellets sintered at temperatures of 1200, 1300, and 1400°C were 0.93, 4.9, and 18 μm.

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An in-situ sulphated-combustion reaction was conducted on the precursor mixture consisting of yttrium nitrate, organic fuels (urea, citric acid and glycine) and 10 mol% ammonium sulphate [(NH₄)₂SO₄] at 500°C. Effect of sulphate addition on yttria particles morphology has been analyzed with respect to the types of fuels. In un-sulphated combustion, the calcined yttria powders showed rectangular particle morphology and low specific surface area. Whereas in sulphated-combustion spherical shaped yttria particles were achieved for glycine fuel. In the case of citric acid fuel, yttria powders with high specific surface area [26 m²/g] were obtained. For all the fuels, the sulphated-combustion reaction produced nanocrystalline yttria powders and they also had primary crystallite size below 4 nm in the as prepared conditions. Upon calcination at 1100°C, these powders attained mean particle size of 50 nm which was confirmed by TEM.

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NiFe₂O₄ powders with large-sized, hollow, and thin wall structures were directly prepared by spray pyrolysis from a spray solution containing citric acid. These as-prepared powders converted into nanosized NiFe₂O₄ powders after post-treatment at high temperatures between 600 and 1000°C. Phase-pure NiFe₂O₄ powders were obtained at post-treatment temperatures between 700 and 1000°C. When the post-treatment temperatures were increased from 700 to 1000°C, the BET surface areas of the NiFe₂O₄ powders decreased from 23.4 to 11.8 m²/g and their mean sizes increased from 47.8 to 94.7 nm, respectively. The saturation magnetizations of the powders changed from 32 to 44 emu/g according to changes in the post-treatment temperatures. The coercivities of the powders post-treated at temperatures of 700 and 800°C were 118 and 130 Oe, respectively.

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Wireless sensor nodes self-powering from an ambient energy source have been widely studied. In particular, the piezoelectric energy harvesting has been the focus of attention, due to its high energy density. For the piezoelectric energy harvesting, a cantilever beam structure has normally been used because of its high efficiency. Since the frequency of environmental vibrations is of the order of hundreds of Hz, which is far below the natural frequency of cantilever type ceramic actuators, the frequency of the cantilever has commonly been adjusted by placing a heavy mass on its end. In order to lower its natural frequency and increase its safety factor, we fabricated a flexible piezoelectric cantilever, which was composed of ceramic on a flexible substrate. However, it was observed that the flexible cantilever was always broken at a certain position. This result indicates that the stress was not homogeneous, and concentrated at the breakage point of the ceramic. To analyze the failure of the ceramic, we measured the inhomogeneous stress distribution on the flexible piezoelectric energy harvester and analyzed it using the ATILA program.

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In this study, by using tin chloride solution as the raw material, a nano-sized tin oxide powder with an average particle size below 50 nm is generated by spray pyrolysis reaction. This study also examines the influences of the reaction temperature and the concentration of raw material solution on the powder properties. As the reaction temperature increases from 800 to 850°C, the average particle size of the generated powder increases from 20 nm to 30 nm, the intensity of XRD peak increases, and the specific surface area decreases. As the reaction temperature reaches 900°C, produced powder of droplet type are composed of nano-sized particles with an average size of 30 nm, while the average particle size of the independent type increases remarkably up to 80-100 nm, and the particle surface becomes more compact. As the reaction temperature reaches 950°C, most of the particles appear mutually independent, while the average particle size is around 70 nm. When the tin concentration reaches 75 g/L, the average particle size of the generated powder is below 20 nm. When the tin concentration reaches 150 g/L, the powder of droplet type are composed of nano particles with an average size around 30 nm, whereas the average size of the independent particles increases up to 80-100 nm. Also, the intensity of XRD peak increases, and the specific surface area decreases. When the concentration reaches 400 g/L, the droplet types are composed of nano-particles with an average size of 30 nm. Also, the intensity of XRD peak increases, and the specific surface area decreases.

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Various TiN-TiB₂-Ti₅Si₃ composites have been synthesized via spark plasma sintering of Ti, BN and Si₃N₄. The reaction process anlaysis indicates that Ti₅Si₃ forms earlier than TiB₂. The reaction heat as well as the Joule heat may prompt the melting of Ti₅Si₃, making it infiltrate into TiN and TiB₂. Thus, the composites can be further densified with the in-situ addition of Ti₅Si₃. For TiN-TiB₂-Ti₅Si₃ composites, the maximum fracture toughness was 4.5 ± 0.3 MPa·m^1/2, and maximum flexural strength was 601.1 ± 28.5 MPa, which were both quite higher than those of TiN-TiB₂ composites. The related toughening and strengthening mechanisms were proposed from microstructural analysis.

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This paper specifically examines control of the residual stress in thin films by design of the stacking structure. For this study, we prepared highly a-, c- oriented PZT(30/70) (: PZT30) thin films using chemical solution deposition (CSD). A PZT30 thin film was deposited on LaNiO₃ (LNO)/Pt/Ti/SiO₂/Si and LNO/SiO₂/Si with different LNO layer thickness to control the thermal stress. An LNO layer was also prepared using CSD on a Pt/Ti/SiO₂/Si substrate and SiO₂/Si substrate. The residual stresses in the PZT30 thin films were estimated using Raman analysis. Furthermore, the dielectric property of samples was measured using an impedance analyzer. Effects of the residual stress on the dielectric behavior were demonstrated through experimentation.

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A new doping method of functional molecules or ions into the optical film of organic-inorganic hybrid materials is demonstrated for the fabrication of optical devises. Capillary Electrophoresis Doping (CED) technique uses the transportation of molecules based on the electrophoresis phenomena in liquid under the electric field. One of the most luminescent dyes, rhodamine 6G (R6G), is incorporated into the hybrid film synthesized from silicon and titanium alkoxides, 3-methacryloxypropyltrimethoxysilane (MAPTMS), tetramethoxysilane (TMOS) and titaniumtetraisopropoxide (TTIP), by the sol-gel process. In order to clarify the migration of R6G molecules into the hybrid materials, pre-bake treatment is applied to the hybrid film before CED treatment. R6G content in the doped region shows complex dependence on the pre-bake time. Structural changes caused by the pre-bake treatment induce different migration phenomena of R6G molecules in hybrid films; elimination of solvents, thermal curing between -C = C- bonds in organic groups.

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Desorption behavior of two proteins; bovine serum albumin (BSA) and egg white lysozyme (LSZ) was followed on hydroxyapatite (HAp) after 72 h-adsorption in a static system, focusing modification effect of carbonate ion on the HAp surface. Desorbed amounts in a 5 mM - phosphate buffer solution (PBS) showed maxima in 2 h for BSA and 1 h for LSZ. The ratio of the maximal desorbed amount to the initially adsorbed one: the desorption rate was chosen as an index of the binding strength of protein to the surface. For LSZ, the desorption rate decreased as increase of the carbonate content, indicating stronger binding. This was ascribed to the increase of the strongly-adsorption site of LSZ: the P site of the c face because the increase of the carbonate in HAp inhibits crystal growth along the c axis and hence increases the c face. On the other hand, any clear dependency was not found for BSA. However, four samples of the various carbonate contents were divided into two groups; one with the higher desorption rate with nearly full and more than full surface coverages and the other with the lower one of 0.42-0.60, assuming to be side-on (multiple-site) adsorption. This suggested that more numbers of weaker binding sites were involved in BSA adsorption on HAp with the higher desorption rate than the lower one.

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On the basis of the thermodynamical approach proposed by Takahashi and Yoshio the Ge-O single bond strengths B_Ge-O of GeO₆ groups denoted as [GeO₆], all bridging GeO₄ groups denoted as [GeO₄]_BO and GeO₄ groups with one non-bridging oxygen denoted as [GeO₄]^-_NBO have been determined for xNa₂O.(1-x)GeO₂ (x = 5-30 mol%) glasses as follows: 323 kJ/mol for [GeO₆], 341 kJ/mol for all bridging [GeO₄]_BO and 460 kJ/mol for [GeO₄]^-_NBO groups. Equation for the calculation of average single bond strengths B_M-O of sodium germanate glasses has been suggested taking into account the contribution of different structural units namely [GeO₆], [GeO₄]_BO and [GeO₄]^-_NBO groups. It has been found that the average single bond strength B_M-O of sodium germanate glasses decreases up to 267 kJ/mol at 25 mol% Na₂O due to the formation of [GeO₆] groups and increases up to 282.5 kJ/mol at 30 mol% Na₂O due to the formation of [GeO₄]^-_NBO groups. The results support the idea that the formation of [GeO₆] groups is probably a main reason for the so-called germanate anomaly. The refractive index based optical basicity Λ(n_o) is sensitive in relation to the germanate anomaly effect and the group basicity follows the sequence: Λ[GeO₄]_BO < Λ[GeO₆] < Λ[GeO₄]^-_NBO. The observed correlation between Λ(n_o) and B_M-O of sodium germanate glasses has been discussed with the presence of Ge⁽⁴⁾-O-Ge⁽⁴⁾, Ge⁽⁴⁾-O-Ge⁽⁶⁾ and Ge⁽⁴⁾-O^-...Na⁽⁶⁾ chemical bonds in the glass structure in which in bracket the coordination number of the cation is given.

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The carbothermal reduction and nitridation (CRN) of α-alumina (α-Al₂O₃) to aluminum nitride (AlN) with gaseous carbon under a flow of nitrogen was investigated by X-ray diffraction and ²⁷Al magic-angle spinning nuclear magnetic resonance (NMR) spectroscopy. The mixture of α-Al₂O₃ and gaseous carbon was obtained by the reaction of aluminum sulfide (Al₂S₃) with carbon monoxide (CO). The AlN formation commenced at 1100°C, which is the lowest temperature reported for AlN formation by the CRN reaction. The involvement of gaseous carbon in the CRN reaction, which has not previously been reported in the CRN reaction, greatly reduced the nitridation temperature of α-Al₂O₃.

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Two types of layered hydroxide zinc o-aminobenzoate compounds with structures of layered basic metal salt (LBMS) were prepared by reacting of zinc hydroxide and o-aminobenzoic acid solution in a temperature range of 40-110°C. The formation reactions, structures, chemical compositions, and exfoliation behavior in alcohol solvents of the layered compounds were investigated by using XRD, TG-DTA, SEM, and TEM. The layered phase with a basal spacing of 1.33 nm has an α-Ni(OH)₂-like structure, and its chemical formula can be written as Zn(OH)_1.27(o-NH₂C₆H₄COO)_0.73·nH₂O. The 1.33 nm layered phase shows plate-like particle morphology. The plate-like crystals can be exfoliated into nanosheet-like particles in alcohol solvents.

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Silicon species have been regarded to be one of the essential trace elements for healthy bone and reported to stimulate osteogenic cells to proliferate and mineralize. In the present work, porous scaffolds of β-tricalcium phosphate (β-TCP) were coated with sol-gel-derived bioactive glass or glass-ceramics of 55S (55 mol% SiO₂, 41 mol% CaO, 4 mol% P₂O₅) composition. Skeletal surfaces of the β-TCP scaffolds were coated with an apatitic compound containing numerous hydroxyl groups through a hydrothermal treatment in distilled water at 140°C for 2 h. After the hydrothermal treatment, the scaffolds were soaked in the 55S sol and then heated at 700-1000°C for 3 h. The 55S glasses with the size of 100 nm in thickness adhered on the skeletal surfaces via the apatitic compound layer. The scaffolds coated with the 55S glass formed hydroxyapatite (HA) layer on their surfaces in simulated body fluid in one day and released silicon species in a cell-culture medium for ≥ 2 w. The formed HA layer adhered strongly on the skeletal surfaces, since they remained on the surfaces after sonication in distilled water for 15 min. Amount of the silicon-species released from the scaffolds was controllable by changing the heat-treatment temperature on the preparation process of the 55S glass. These results indicate that the porous β-TCP scaffolds coated with the 55S glass have high potential as materials for bone reconstruction and propose a useful method for preparing a new scaffold having functionalized surface using the sol-gel-derived glasses.

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The surface structure developed on Ti metal after an NaOH and heat treatment and subsequent soaking in a simulated body fluid (SBF) was investigated using cross-sectional analysis involving SEM observations and EDX analysis, as well as an outer surface analysis involving SEM observations, thin-film X-ray diffraction, and Raman spectroscopy. A 1 μm-thick layer, which consisted of lathlike sodium hydrogen titanate (Na_xH_2-xTi₃O₇) elongated perpendicular to the surface, formed on the surface of the Ti metal after the initial NaOH treatment. This layer gradually changed into Ti metal at the boundary. The surface layer was densified by the subsequent heat treatment, accompanied by a transformation of the sodium hydrogen titanate into sodium titanate (Na₂Ti₆O₁₃), rutile, and anatase. The scratch resistance of the surface layer significantly increased after the heat treatment. When this Ti metal with a modified surface was soaked in SBF, apatite began to precipitate in the interior of the surface layer, filled the interspaces of the lathlike phases to integrate with the latter giving a dense composite structure, and grew over the surface layer.

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Using multi-pass extrusion process, a t-ZrO₂ support tube for small tubular solid oxide fuel cell (SOFC) was fabricated. After burning out of extrusion binder, lubricant and pore former, SOFC functional layers have been coated on the tube by slurry dip coating method. The cell configuration was composed of NiO-8YSZ, 8 mol% yttria stabilized zirconia (8YSZ), Gd_0.2Ce_0.8O_1.9-x, (GDC) and La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF) on the t-ZrO₂ supported tube as anode, electrolyte, interlayer and cathode, respectively. Dense microstructure of electrolyte was achieved by co-sintering. Maximum power density of 349 mW/cm² was obtained at 850°C using pure H₂ as fuel and stagnant air. The cell showed stability for a time period of 100 h at 850°C.

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One-dimensional periodic sub-wavelength structures (SWSs) with a period of 300 nm were fabricated on a bismuth germano-borate glass plate by a direct glass nanoimprint method using SiC molds. The borate glass had a refractive index of 1.82 at 587.6 nm wavelength, an internal transmittance higher than 80% at a thickness of 3 mm in the visible wavelength region, and a deformation temperature of 468°C. SWSs with height of a few hundred nanometers were simultaneously fabricated on both surfaces of the glass plate by the glass nanoimprint at 488°C for 120 s with 8 MPa in pressure. The SWSs showed form birefringence. A phase retardation of 0.23 λ was observed between transverse electric (TE)- and transverse magnetic (TM)-polarized beams at 400 nm wavelength.

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The chemical durability of a typical low k LTCC material consisting of zinc calcium aluminoborosilicate glass and alumina filler was studied. Leaching experiments were performed by measuring weight loss of the samples in selected acid and base aqueous solutions of HCl, H₂SO₄ and KOH at two different temperatures of 25° and 80°C. The leaching performance was found to depend strongly on the type of leaching solution, duration and temperature. The LTCC sample was most stable in 10 vol% KOH with a minimal weight loss of ∼0.43% even after 300 min at 80°C. At the same condition, both cases of 10 vol% HCl and 10 vol% H₂SO₄ exhibited serious weight losses greater than 30%. It was interesting to observe that the high capability of leaching in the acid solutions originated significantly from the leaching of crystalline anorthite (CaAl₂Si₂O₈) phase.

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