A new process for preparing particles of superconducting oxides was developed by using an aerosol flow reactor in which aqueous solutions of corresponding metal nitrates are atomized and their droplets are evaporated and thermally decomposed. The particles obtained from this process are spherical and their size can be controlled by changing the concentration of the aqueous solutions. For the Y-Ba-Cu-O system, the particles having an orthorhombic YBa2Cu3O7-x phase can be formed directly at the decomposition temperatures from 900 to 1000ºC. The bodies sintered from these particles show the offset temperature of the superconducting transition at 87 K. For the Bi-Ca-Sr-Cu-O system, the superconducting particles of the Bi2Ca2Sr2Cu3Ox and Bi1.8Pb0.2Ca2Sr2Cu3Ox compounds were prepared directly. The crystalline phases of the particles were found to be very sensitive to oxygen pressure in the carrier gas as well as to the decomposition temperature. The sintered bodies from the powders of Bi1.8Pb0.2Ca2Sr2Cu3Ox had onset temperature of 110 K and offset temperature of 80K.† This report was originally printed in J. Soc. Powder Technology, Japan. 26(3), 146-150 (1989) in Japanese, before being translated into English by KONA Editorial Committee with the permission of the editorial committee of the Soc. Powder Technology, Japan.

Superionic glasses xCuI-(1-x)[Cu2MoO4-CuPO3] were prepared and studied by infrared reflectance spectroscopy to investigate the structure of the oxyanion matrix and the type of sites occupied by copper ions. The study was complemented by the consideration of glasses 0.67CuI-0.33[Cu2MoO4-Cu3PO4] and xCuI-(1 - x)[Cu2O-nP(2)O(5)] with n = 0.33, 0.50, 1.0. The oxyanion structure of glasses xCuI-(1 - x)[Cu2MoO4-CuPO3] was found to involve discrete PO43-, P2O74- and MoO42- units, where P and Mo are 4-fold coordinated to oxygen, and molybdate octahedral species which have the MoO3 stoichiometry and are linked by Mo-O-Mo bridging bonds. Despite the nominal metaphosphate composition (CuPO3) of these glasses the spectra gave no signature for metaphosphate structures based on the PO3- unit. Also, increasing amounts of CuI were found to favor the creation of PO43- and MoO3 species at the expense of P2O74- and MoO42-. These findings were explained by the acidity order P2O5 > MoO3 and the need to accommodate the bulky CuI in the glassy matrix, a process facilitated by condensed MoO3 octahedral species. Cu ions were found to be present as monovalent cations and to occupy oxide and iodide sites. The latter sites organize into CuI-like pseudophases at high CuI contents, in agreement with the conduction pathway model for superionic glasses.

Many new glasses composed of AgI, Ag2O and oxides, MxOy, where MxOy is B2O3, SiO2, GeO2, P2O5, V2O5, As2O5, CrO3, SeO3 or MoO3, were found. Among these oxides, the B2O3-based glasses, that is, the AgI-Ag2O-B2O3 glasses have several unique properties such as (a) very wide glass forming regions, (b) high glass transition temperatures, (c) network structure with BO3 and BO4 groups, and (d) high conductivities of 10(-2) to 10(-7) S cm(-1) at room temperature. The high temperature form of AgI, alpha-AgI, was stabilized in the borate glasses in two ways; one was the rapid melt quenching, and the other was the annealing of glasses at a suitable temperature below the a a transformation temperature (147 degrees C) for AgI. The latter technique is now usefully applied for the development of glass ceramics as the solid electrolytes for all solid state lithium secondary batteries. Tin oxide containing borate and borophosphate glasses were prepared by the mechanical milling technique as well as melt quenching. These new glasses were proved to work as large capacity negative electrodes for Li+ ion secondary batteries. The capacities and also the glass transition temperatures were strongly related to the amount of four coordinated boron.

The crystallization of TiO2 in monolithic SiO2-TiO2 (SiO2>TiO2) gels by annealing has been investigated. The temperatures of the crystallization of TiO2 to anatase and anatase-to-rutile phase transition were considerably raised with the addition of SiO2. It is supposed that the anatase-torutile phase transition is primarily controlled by the grain size of the crystals. TiO2(B), one of the TiO2 polymorphs, was formed as one of the first crystalline phase in SiO2-TiO2 gels at 800-900°C. Transmission electron microscope observations revealed that TiO2(B) nanocrystallites with a size of 5-10 nm were dispersed in amorphous SiO2 matrix. TiO2(B) nanocrystallites did not grow larger but transformed to anatase at higher temperatures. It is supposed that the nucleation and stability of TiO2(B) are enhanced with the presence of surrounding SiO2, presumably by a low interfacial energy.

One of the features of the sol–gel techniques is closeness to the industrial applications. Another feature is the variation of shapes of obtained materials like bulk, fiber, coating film, powder and so on. Among them, the author has focused on research of the sol–gel coatings on various substrates for practical applications as well as the fundamental research under the collaboration with industry. In this review, results of such research will be presented. These include (a) protective coating on metal sheets, (b) micropatterning on glass substrates, (c) water-repellant coating on windshields, (d) colored coating on glass bottles for easy recycling, (e) superhydrophobic and superhydrophilic coating on glass plates, and (f) anti-reflective coating on glass lenses for cameras. Some were highly successful, and some were not, of course. The author also contributed to the foundation of The Japanese Sol–Gel Society in 2003. The activities of The Society in these 8 years are introduced.

Electronic states of Li ions during the ionic jumps in the Li3N crystal was discussed on the basis of the first principle molecular orbital calculations. The movements of the Li ions were simulated by several model clusters with different positions of the moving cation. The net charge of the moving Li ion and the total bond overlap population between the moving Li ion and the other ions were used for discussion of chemical bonding of the moving Li ion. Furthermore we have estimated the local cluster energy (LCE) to compare the energy change in the different moving path of the Li ion. The total bond overlap population of the moving Li ion along the conduction path changed smaller than those of the other paths. On the other hand, the changes of the net charges of the moving Li ions were similar in any paths. The change of the LCE in the model cluster of the conduction path was much smaller than that in another model cluster. As the results, the smaller change of the total bond overlap population of the moving Li ions played an important role for the fast ion movement in the Li ion conductors, rather than the change of the net charge of the moving Li ions. This bonding state of the moving Li ions is one of the characteristics of the electronic state in Li ion conductors.

Alumina thin films, with roughness of 20–50 nm and pseudoboehmite nanocrystals precipitated on the surface, were formed through immersion of porous alumina gel films in hot water. By coating hydrolyzed fluoroalkylsilane on such a thin film with slight roughness, a superhydrophobic surface with high transparency was obtained. Additives such as hydrochloric acid, sodium hydroxide, sodium chloride, manganese chloride, ethanol and ethylene glycol were dissolved in the hot water, and the effects of these additives on pseudoboehmite nanocrystal formation during hot water treatment were examined. Pseudoboehmite nanocrystals were formed at pH = 5.5–8.0 when an acid or a base was added to water. The addition of inorganic salts and alcohol diminished the boehmite nanocrystal formation. These results suggest that the boehmite nanocrystals were formed through a dissolution and re-precipitation process.

Using melt quenching, SnO–P2O5 glasses were synthesized, and then characterized as negative electrode materials for lithium secondary batteries. The electrochemical cell Li/the 67SnO·33P2O5 (mol%) glass maintained reversible capacity of about 400mAhg−1 for 20 cycles. The cell’s cycle performance was better than those of cells using Sn-based crystals such as Sn, SnO, and SnO2 as working electrodes. The local structure of the 67SnO·33P2O5 glass after lithium insertion and extraction was analyzed. 7Li MAS-NMR measurements revealed that the Li–Sn alloy was formed during the first lithium insertion to the glass and that alloying–dealloying of the Li–Sn domain occurred during charge–discharge cycling. The glassy matrix surrounding the alloy was investigated using 31P MAS-NMR. The P2O74- group might be changed to PO43- and P2O64- groups by the first lithium insertion to the glass. The formed phosphate groups remained after the consecutive lithium extraction process. An all-solid-state cell with the 67SnO·33P2O5 glass exhibited the discharge capacity of 750mAhg−1 at the first cycle, which is greater than that of a cell with the 50SnO·50B2O3 glass.

Electronic states of monovalent ions in superionic conductors such as Li3N, as well as the lithium sulfide superionic conducting glasses, were calculated by the DV-X alpha cluster method. The movements of the cations were simulated by several model clusters with different positions of the moving cation. The net charge of the moving cation and the total bond overlap population (TBOP) between the moving cation and other ions were used for discussion of chemical bonding of the moving cation. In the Li3N crystal, the TBOP of the moving cation along the conduction path changed less than those of the other paths. On the other hand, the changes of the net charges of the moving cations were similar in all paths. Furthermore, the relationship between ionic conductivity and the differential total bond overlap population (DBOP) was discussed in the lithium sulfide superionic conducting glasses. The cluster models were constructed by the coordination number reported by experimental methods and the bond length estimated from the ionic radii of each ion. Especially the relationship between ionic conductivity and the differential bond overlap population was discussed for the sulfide-based lithium ion conducting glasses in the systems Li2S-SiS2-Al2S3 and Li2S-SiS2-P2S5. In these glasses, the DBOP with the movement of the lithium ion had good negative correlations with the ionic conductivity and positive correlations with the activation energy obtained by the experimental measurements. In any case, the smaller change of the TBOP of the moving cations played an important role in the fast ion movement in the superionic conducting glasses, rather than the change of the net charge of the moving cations. This bonding state of the moving cations is one of the characteristics of the electronic state in superionic conductors.

The shape of the precipitates on sol–gel derived SiO2–TiO2 coatings at the negative electrode changed from granular to ramiform by applying an electric field to the substrates during a hot water treatment, whereas such changes in the shape of titania nanocrystals with the electric field were not observed at the positive electrode. The granular and ramiform precipitates were identified as anatase (TiO2) and hydrated titania (n(TiO2) · mH2O), respectively. The ramiform shape of the titania precipitates became significant with increasing the applied voltage, while the coatings gradually became dark-colored due to the reduction of Ti4+ to Ti3+. The coatings with ramiform precipitates showed an excellent wettability for water.

The antireflective (AR) properties of Al(2)O(3) thin films with small roughness on soda-lime silica glass substrates were investigated. By immersing porous Al(2)O(3) thin films in hot water, nanocrystals of pseudoboehmite were formed on the film surface. The reflectance of the Al(2)O(3) films treated with hot water for 30 min was less than 0.5% in the wavelength region of 360-620 nm. The Al(2)O(3) films with small roughness resulting from the hot water treatment become denser from their surface to the interface with the substrate, and the refractive index gradient brought by the structure results in excellent AR properties. (c) 2006 Elsevier B.V. All rights reserved.

Electronic states of the sulfide-based lithium ion conducting glasses were calculated by the DV-Xα cluster method. The cluster models were constructed by the coordination number reported by experimental methods and the bond length estimated from the ionic radii of each ion. The movement of the Li ion was simulated by several model clusters with different positions of the moving ion. The relationship between ionic conductivity and the differential total bond overlap population (DBOP) was discussed for the sulfide-based glasses in the systems Li2S–SiS2–Al2S3 and Li2S–SiS2–P2S5. In these glasses, the DBOP with the movement of the lithium ion had good negative correlations with the ionic conductivities and positive correlations with the activation energies obtained by the experimental measurements. In any cases, the smaller change of the total bond overlap population of the moving cations played an important role for the fast ion movement in the superionic conducting glasses. This bonding state of the moving cations is one of the characteristics of the electronic state in the sulfide-based lithium ion conducting glasses.

Highly Ag + conductive glasses in the system AgI-Ag 2 O-B 2 O 3 were prepared by mechanochemical synthesis using a high energy planetary ball mill apparatus. The glass forming region for the composition series ofxAgI.(100-x)(0.5Ag 2 O. 0.5B 2 O 3 ) (mol%) was determined. The mechanically milled sample with 60 mol% AgI exhibited the highest conductivity of 1.7x10 -2 Scm -1 at room temperature, which is comparable to the conductivity of the corresponding melt quenched glass. The glass transition temperature (T g ) of the milled sample was lower than that of the corresponding melt quenched glasses, but the T g approached the T g of the quenched glass with increasing milling time. The local structure, in particular the fraction of four-coordinated BO 4 units, closely related to electrical and thermal properties of the AgI-based borate glasses prepared by mechanical milling as well as by melt quenching.

Amorphous Al2O3−ZnO thin films with various Zn/Al ratios were prepared on glass substrates by the sol−gel method with a heat treatment at 400 °C for 30 min followed by immersion of the films in distilled water at 100 °C to form nanocrystalline Zn−Al layered double hydroxide (LDH) with hexagonal structure. Zn−Al LDH nanocrystals were precipitated on the amorphous Al2O3−ZnO films with various Zn/Al ratios, and the maximum amount of nanocrystals was formed on the film of the Zn/Al atomic ratio of unity. Zn−Al LDH crystals with the size of 200−500 nm have been precipitated on glass substrates through hot water treatment at temperatures lower than 100 °C.