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Perovskite Pb(Fe 1/2 Nb 1/2 )O 3 (PFN) coating films have been prepared on Si(100) and MgO(100) single crystal, and silica glass substrates by the sol-gel method using Nb(OC 2 H 5 ) 5 , Fe(NO 3 ) 3 (DOT)9H 2 O, and Pb(OC 3 H 7 i ) 2 and Pb(CH 3 COO) 2 (DOT)3H 2 O as starting materials. Five solutions with different preparation routes were used for dip-coating. Starting materials, mixing sequence of starting materials and substrate materials influenced the formation of PFN perovskite in the resultant coating films to a great extent. The use of Pb(CH 3 COO) 2 (DOT)3H 2 O as lead sources and MgO(100) single crystal substrate lead to the direct formation of PFN coating films of single-phase perovskite. The results obtained are discussed in terms of macromolecules formed in coating solutions.

The sol-gel researches currently done in Japan have been introduced in relation to the two topics; (1) glass research and (2) fiber drawing. In the first topic, the application to the preparation of optical and non-linear optical functional materials is emphasized. In the second one, the hydrolysis and condensation conditions which give rise to a spinnable sol are briefly described and subsequently a number of examples of glass and ceramic fibers which have been made so far in Japan are given.

The sol-gel method using lithium and boron-n-tributoxide as starting materials has been applied to prepare Li2B4O7 coating films on silica glass, silicon and sapphire single crystal substrates. The effects of the amounts of water and acid added to coating solutions, and the kinds of substrate on the crystallization of Li2B4O7 coating films were fully investigated. It was found that a sufficient amount of water is required for obtaining well-crystallized Li2B4O7 films of single phase, the addition of acids such as hydrochloric and acetic acids to the coating solution suppresses crystallization up to 600°C and gives highly oriented Li2B4O7 single phase films on further heating at 800°C.

Glass-ceramic A-W, containing crystalline apatite and wollastonite in a MgO-CaO-SiO2 glassy matrix shows high bioactivity as well as high mechanical strength, but other ceramics containing the same kinds of crystalline phases in different glassy matrices do not show the same bioactivity. In order to investigate the bone-bonding mechanism of this type of glass-ceramic, surface structural changes of the glass-ceramics after exposure to simulated body fluid were analyzed with various techniques. A solution with ion concentrations which are almost equal to those of the human blood plasma was used as the simulated body fluid, instead of Tris-buffer solution hitherto used. For analyzing the surface structural changes, thin-film x-ray diffraction was used in addition to conventional techniques. It was found that a bioactive glass-ceramic forms a Ca, P-rich layer on its surface in the fluid but nonbioactive ones do not, and that the Ca, P-rich layer consists of carbonate-containing hydroxyapatite of small crystallites and/or defective structure. These findings were common to those of Bioglass-type glasses. So, we conclude that the essential condition for glass and glass-ceramic to bond to bone is the formation of the surface apatite layer in the body environment but it is not essential to contain apatite within the material. Bioactivity of glass and glass-ceramic can be evaluated in vitro by examining the formation of the surface apatite layer in the simulated body fluid described above.

Sol-gel reaction of tetramethoxysilane (TMOS) under highly acidic conditions with a limited amount of water provides highly porous monolithic silica gels composed of micrometer-sized particles1–3). Because of the continuous large pores and particles, these gels and heated derivatives may be suitable for porous materials which can be used as filters or supports for catalysts and enzymes. For these uses, surface characteristics of the gels should be controlled. Since the amount of water for hydrolyzing TMOS in the starting solutions is limited, some of alkoxy groups may be left to be hydrolyzed at the time of gelation and water in the atmosphere may affect the nature of surfaces of the large particles of the gels during drying. In the present study, the surface properties of the gels have been investigated by BET analysis and electeon microscopic observation as a function of drying time.

The mixed alkali effect on electrical conductivity, that is, the reduction of conductivity due to alkali mixing, was observed in Na2O–K2O–Ga2O3–TiO2 glasses, which are nonconventional in the sense that glass-forming oxides defined by Zachariasen are not involved. The magnitude of the reduction in conductivity of the present glasses due to alkali mixing was similar to that of corresponding mixed alkali silicate and phosphate glasses. The activation energy for electrical conduction showed a maximum around the composition Na/(Na + K) = 0.5, where the conductivity was at a minimum.

Third harmonic generation from nonconventional MOx‐PbO‐GaO1.5 (M=Ti,Nb,W) glasses have been measured. The nonlinear susceptibility, χ(3), of these glasses at 0.635 μm are about 30 times higher than that of SiO2 glass at the same wavelength. It has been found that TiO2 is most effective in increasing refractive index and χ(3).

Ferroelectric Pb(Fe0.5Nb0.5)O3(PFN)-PbTiO3(PT) thin films have been prepared on silica glass and silicon single crystal substrates by the sol-gel method using lead acetate, iron nitrate, niobium ethoxide and titanium tetraisopropoxide as precursors. It has been found that 38 mol% excess lead must be added to a starting solution to obtain single phase perovskite PFN coating films, while single phase perovskite 0.2PFN·0.8PT coating films can be prepared from the corresponding stoichiometric starting solution. The coating film shows a dielectric constant of about 500-1100 and dielectric loss of about 0.06-0.18 at 1000 Hz.

Effects of the substitution of sulfur for oxygen on the structure and electrical properties of La1.84Sr0.16CuO4 superconductor have been studied. It was found that the superconducting transition temperature decreases, the temperature dependence of electrical resistance at low temperatures becomes semiconducting and the electrical resistance increases with increasing sulfur content. The crystal structure at room temperature changed from tetragonal to orthorhombic, while the in-plane lattice constants a and b increased and the lattice constant c decreased with increasing sulfur content.

Superconducting Bi-Sr-Ca-Cu-O coating films have been prepared on YSZ (yttria-stabilized zirconia) and Al2O3 substrates by the sol-gel method using an aqueous solution of metal acetates containing tartaric acid. A film of 20 µm thickness on the YSZ substrate showed T c(onset) at 115 K and T c(end) at 79 K, consisting of Bi2Sr2CaCu2O x crystals with the c-axis perpendicular to the substrate. The reaction between the film and the YSZ and Al2O3 substrates produced CaZrO3 and CuAl2O4, respectively, during heat treatment, which suppresses the formation of superconducting phases and causes the degradation of the superconducting properties of the films.

In order to find the role of N,N-dimethylformamide (DMF), a newly found DCCA (drying control chemical additive), in producing silica gel monoliths by the sol-gel method, microstructures of the silica gel monolith prepared from tetramethoxysilane (TMOS) solutions containing DMF and formamide, respectively, have been examined. Dry gels prepared from the solutions containing DMF and formamide had larger pores, which was interpreted to be one of the effects of the DCCA in suppressing occurrence of cracks and fractures in the process of drying wet gels. When drying gel discs prepared from solutions containing DMF were exposed to the vapors and, subsequently liquids of DMF, formamide, methanol and water whose surface tensions are different from each other, cracks were generated for formamide and water having high-surface tensions and no cracks were produced for DMF and methanol. This was interpreted to indicate that the low surface tension of DMF may be one of the effects in protecting the drying gel from crack generation. It was assumed that DMF vaporizes at last during the drying process and weakens the capillary force exerting on the silica network structure.

For the purpose of analyzing the crystallization process of glass by DTA, the modified Kissinger-type equation was derived on the basis of the nucleation and growth equations, and the validity of the equation was ascertained by applying to the crystallization of Li 2 O·2SiO 2 glass whose kinetic data regarding crystallization are already well-known. The modified Kissinger-type equation is identical with the so-called Kissinger equation only when the crystallization starts at the surface and grows towards the inside of the glass one-dimensionally. The conditions required for applying the Kissinger plot or modified Kissinger-type plot to the crystallization of glass were discussed, and it was concluded that the crystallization mechanism should be known in order to obtain the meaningful activation energy.

Methyltriethoxysilane and ethyltriethoxysilane were treated with Amberlyst 15 cation-exchange resin in the presence of hexamethyldisiloxane at 40°C. The reaction involves partial or full replacement of the ethoxyl group by trimethylsiloxyl to give RSi(OEt) n (OSiMe 3 ) 3− n ( n = 0, 1, 2). The degree of substitution depends mainly on the ratio in which hexamethyldisiloxane and alkyltriethoxysilane are mixed. The nature of alkyl group in an alkyltriethoxysilane had little effect on the degree of substitution at a given mixing ratio.

The structure of Na 2 ONb 2 O 5 Ga 2 O 3 and BaONb 2 O 5 Ga 2 O 3 glasses was investigated by Raman spectroscopy and compared with that of Cs 2 O (or K 2 O)Nb 2 O 5 Ga 2 O 3 glasses. It is shown that Ga 3+ ions form mainly GaO 4 tetrahedra with no non-bridging oxygens and Nb 5+ ions mainly form severely distorted NbO 6 octahedra in the Na 2 ONb 2 O 5 Ga 2 O 3 glasses, like in the Cs 2 O (or K 2 O)Nb 2 O 5 Ga 2 O 3 glasses. In BaONb 2 O 5 Ga 2 O 3 glasses, there are a considerable number of less distorted NbO 6 octahedra with no non-bridging oxygens in addition to those structural units found in the above alkali oxideNb 2 O 5 Ga 2 O 3 glasses.

The kinetics of hydration of CaO-Al2O3-P2O5 and Na2O-CaO-B2O3-Al2O3 glasses in an autoclave at high temperatures and pressures have been investigated. A linear time dependence of the depth of hydrated layer has been found for the glasses used in the present study. This implies that the hydration process is governed by the chemical reaction at the interface between the unhydrated and the hydrated glass phases. It is indicated that the hydration of the phosphate glasses may occur as a result of hydrolysis of glass constituents to form orthophosphate crystals. Water vapour can easily reach the interface through the crystalline aggregates, which are loosely packed. Cabal glasses which do not contain any alkali oxides have shown quite a high resistance to water. Substitution of sodium for calcium has resulted in deterioration of the chemical durability of cabal glasses. This can be explained by the difference in stability between sodium and calcium ions in the hydrated layer.

The occurrence of the spinnability in the sols prepared by the hydrolysis and polycondensation of tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane and tetranormalbutoxysilane has been investigated. It has been found that the spinnability appears at high viscosities in all of these solutions when the H2O/Si(OR)4 mole ratio of the starting solution is 2 and an acid is used in the hydrolysis reaction. It has also been shown that the spinnable solutions show the Newtonian behavior at high viscosities.

The effects of incorporation of nitrogen on the electrical conductivity and the chemical durability in the R-Si-O-N oxynitride glasses (R=Li and Na) have been systematically investigated. The electrical conductivities of these oxynitride glasses are enhanced and the chemical durabilities to the acidic and alkaline aqueous solutions are drastically improved as the nitrogen content increases. The extent of the changes in the electrical conductivity and the activation energy for conduction due to the nitrogen incorporation are greater for the Li-Si-O-N oxynitride glasses than for the Na-Si-O-N system. The experimental results are discussed from the viewpoint of the increased covalency of the chemical bonding in the glass network by the formation of covalent Si-N bonding.

The effects of mixing of two dissimilar alkalis on various properties of heavy-metal fluoride glasses are reviewed on the basis of our studies. Remarkable effects are found in the electrical conductivity and dielectric loss, and minor but significant effects are found in Vickers hardness, elastic constants and dielectric constant. No appreciable effect is found in density, refractive index, thermal expansion coefficient, glass transition temperature and chemical durability.

The coordination state of Ti4+ and Ge4+ ions in Na2O-TiO2-GeO2 glasses has been investigated. Upon crystallization of the glasses, the thermodynamically metastable hexagonal GeO2 crystals containing 4-fold coordinated Ti4+ ions together with stable Na4Ge9O20 crystals containing 6-fold coordinated Ti4+ ions were precipitated. The distribution of Ti4+ ions between these two crystalline phases is a reflection of the coordination state of Ti4+ ions in the starting glass. The majority of Ti4+ ions are in 6-fold coordination at a small TiO2/Na2O ratio and they are contained in Na2Ge9O20, while the majority of Ti4+ ions are in 4-fold coordination at a large TiO2/Na2O ratio and they are contained in GeO2 crystals. Concentrations of 4- and 6-fold coordinated Ti4+ ions have been confirmed to be similar to that in Na2O-TiO2-SiO2 glasses as measured by the X-ray absorption spectrometry of Ti4+ ions. The coordination state of Ge4+ ions in the glasses have been examined by infrared (IR) spectrometry. It is found that in Na2O-TiO2-GeO2 glasses Ge4+ ions have 6-fold coordination preferentially, while Ti4+ ions have 4-fold coordination except at small contents of TiO2, indicating that the addition of TiO2 to Na2O-GeO2 glasses leads to the replacement of 4-fold coordinated Ge4+ ions by 4-fold coordinated Ti4+ ions.

The sintering of three kinds of dried gels with different microstructures prepared from the tetramethoxysilane (TMOS) solutions containing N,N-dimethylformamide (DMF) with varying [H2O]/[TMOS] mole ratios and different catalysts was investigated by measuring the pore size distribution, the Vickers hardness, the linear shrinkage and the apparent density of the gels heated to various temperatures. The marked shrinkage of the pores started at temperatures above 900 °C. The temperature required for the conversion of a gel to a pore-free silica glass depended on the average size of the pores contained in the dried gels; the average pore sizes of about 50 A, 75 A and 100 A corresponded to 1040 °C, 1060°C and 1080°C, respectively. The Vickers hardness, the linear shrinkage and the density of the gel showed a corresponding change with a change in heating temperature.

Monolithic dried silica gels were synthesized from tetramethoxysilane (TMOS) solutions using N, N-dimethylformamide (DMF) as a drying-control chemical additive. Solutions of the system TMOS-DMF-CH3OH-H2O-NH4OH (or HNO3) with varying amounts of catalyst, concentrations of DMF and [H2O]/[TMOS] molar ratios were reacted to obtain dried gel monolith, in order to find an optimum composition. A crack-free cylindrical rod of 32mm in diameter and 120mm in length could be obtained from the solutions of the composition 1 TMOS⋅1 DMF⋅2 CH3OH⋅10 H2O⋅5×10-4NH4OH in mole and some other compositions. The pore size distribution varied with the kind and amount of catalyst, the concentration of DMF, and the [H2O]/[TMOS] molar ratio. The beneficial role of DMF in producing crack-free dried gel monolith was attributed to the effect of keeping the average pore size of the gel large and of lowering the surface tension of liquid filling pores in the drying gel. When the composition of the starting solution was appropriate, the dried gel monolith could be converted into transparent silica glass without cracking and bloating by heating to 1050°C and holding there for more than two hours. The change of gel structure of the dried gel was investigated by infrared and Raman spectroscopy.

The hydrolysis and condensation reactions of Si(OC2H5)4 (TEOS) at 80°C in the TEOSH2OC2H5OHHCl solutions with H2O/TEOS molar ratios (r) from 1.0 to 2.0 were followed by gas chromatography (GC) and measurement of molecular weight ( M n ) of the hydrolyzates, in order to explain the viscosity change of the solutions. It has been found that the siloxane oligomers with average polymerization degree (n) from 2 to 7 are formed in the early stage of reaction and undergo condensation to form higher polymers. The n and the number of silanol groups of the oligomers are increased with increasing r. The fact that the solution viscosity increased once rapidly around the so-called gelation point followed by a sluggish increase with the increase of reaction time for an r of 1.7, while it increased rapidly without a break till gelation for an r of 2.0, was attributed to fewer silanol groups and higher steric hindrance as a result of more −OC2H5 groups remaining in the oligomers for an r of 1.7.

Sols and coatings of the composition 70V 2 O 5 ·30GeO 2 have been prepared by the sol-gel method using VO(i-OC 3 H 7 ) 3 and Ge(OC 2 H 5 ) 4 as the starting materials and the dip-coating technique. The stability of the sols with different water/alkoxide ratio ( R ) is studied by means of spectroscopy. Sols with R = 3 remain clear for one month after they are diluted 20 times with water. The coatings are heated to various temperatures both in air and under vacuum. The transmission spectra of the heated coatings reveal that thin films obtained by heating the coatings under vacuum at 500° C show apparent reversible transmission hysteresis with temperature indicating the possibility of using them as erasable optical storage media.

A method for determining the activation energy for crystal growth was calculated on the basis of the heat balance in the differential thermal analysis (DTA) measurements and the mechanism of nucleation and growth. The theoretical analysis showed that the term ln[C pd(δT)/dt+KδT] should be a linear function of l/T, whereC p is the heat capacity of sample and sample holder,K is the heat transfer coefficient,δT is the temperature difference between the sample and reference substance andt is the time. The energy term,E D, obtained by multiplying the slope of the resulting straight line byR is indicative of the activation energy for crystal growth. It was shown thatE D should be three times the activation energy for crystal growth when bulk nucleation is dominant, and equal to that for crystal growth only when surface nucleation predominates. The result of the analysis was tested by comparing the experimentally determinedE D's with the activation energy for viscous flow, which was known to represent that for crystal growth. TheE D for Li2O·2SiO2 glass with dominant bulk nucleation, approached three times the activation energy for viscous flow, as the heating rate in DTA decreased. TheE D for 33.3Li2O·66.7SiO2·3TiO2 glass with dominant surface nucleation approached the activation energy for viscous flow as the heating rate increased, suggesting the validity of the analysis.

The shape of particles present in the alumina sols prepared from inorganic salts was examined by transmission electron microscopic observation and related to the rheological property and fiber drawing behavior of the sols. It was found that fibers could be drawn in the viscosity range of 1–100 Pa·s from the sols in which long-shaped particles were found, while no fibers could be drawn from the sols containing round particles. It was also found that non-spinnable sols showed relatively large structural viscosity, whereas spinnable sols showed Newtonian flow or very little structural viscosity.

Raman spectra of BaO-SrO-Ga 2 O 3 and MgO-SrO-Ga 2 O 3 glasses have been measured to investigate the structural role of alkaline earth ions in the gallate glasses. From the comparison of the intensities of the pertinent Raman scattering bands it has been found that Mg 2+ ions have a structural role different from Sr 2+ and Ba 2+ ions in the gallate glasses. It has been shown that substitution of MgO for SrO in MgO-SrO-Ga 2 O 3 glasses decreases the concentration of non-bridging oxygens, indicating that Mg 2+ ions are favorable neither to make non-bridging oxygens in GaO 4 tetrahedra nor to compensate the excess negative charge of GaO 4 tetrahedra. It has also been found that substitution of BaO for SrO in SrO-BaO-Ga 2 O 3 glasses changes the glass structure continuously. The significance of the difference in the structural role in gallate glasses between Mg and the other alkaline earth cations such as Ca, Sr and Ba have been related to the different glass-forming tendencies of the alkaline earth gallate systems.

Raman spectra of R2O-Ga2O3-TiO2 glasses, where R is Na, K, or Cs, have been measured and the structure of the glasses has been discussed on the basis of Raman spectroscopy and the X-ray radial distribution analysis on the binary R2O-Ga2O3 and R2O-TiO2 glasses reported previously. It has been confirmed that both Ga3+ and Ti4+ ions are four-coordinated by oxygens as in the respective binary glasses. It was found that the strength of the bridged Ga-O bonds decreases and nonbridging oxygens are formed with increasing R2O and TiO2 content. The Ti-O bond strength has been found to be higher for the glasses containing larger alkali ions. It was also found that in Na2O-containing glasses the Ti-O bond becomes strong with increasing Na2O content, whereas in Cs2O-containing glasses the Ti-O bond becomes weak with increasing Cs2O content.

The K2O·4GeO2 glass with the highest content of 6-fold coordinated Ge4+ ions (N6) in the K2O-GeO2 system was subjected to the structure analysis by X-ray diffraction using the pair function method. The real K2Ge4O9 crystal and a hypothetical “spiral type” K2Ge4O9 crystal with the same composition and N6 as the glass were selected as the starting structure models. In the former model, the “isolated” GeO6 octahedra are linked to GeO4 tetrahedra in Ge3O9 rings by sharing corner-oxygens. The latter has “isolated” GeO6's linking via oxygens at corners to GeO4's in (GeO3)n chains. The radial distribution function calculated using the latter model agreed well with the observed one as in the case of the Na2O·4GeO2 glass.

TiO2 films up to about 2μm thick have been prepared on a nesa glass substrate by dip-coating technique using the TiO2 sol solution derived from Ti(O-i-C3H7)4. Photoelectrochemical properties of the TiO2 film electrode thus obtained have been investigated as a potential candidate for solar energy conversion device. The results obtained are summarized as follows:(1) The sol-gel derived TiO2 film shows a very large photocurrent due to porous surface structure and a maximum (-14mA cm-2) at about 1.8μm in thickness. A decrease in the photocurrent of the TiO2 film above 1.8μm thick is due to an increase in the resistance.(2) An additional heating at 500°C improves remarkably the photocurrent of the TiO2 film, although too long heating rather deteriorates it. These results are explained on the basis of the changes in the surface structure and carrier concentration with the additional heating time.

A zirconia hydrogel prepared by dialysing ZrOCI2 aqueous solution against water buffer was unidirectionally frozen in a cylindrical polyethylene cell which was immersed in a -78° C cold bath at various rates. Freezing rate,R, and temperature gradient,G, at the frozen gel front were continuously measured during freezing. It was found that zirconia fibres longer than 20 mm are formed whenG/R = 2 to 8° C h cm−2. Either lower or higherG/R values gave only fragmental zirconia. The diameter,d, of the long zirconia fibres was changed from 25 to 55 μm with the temperature gradient and the freezing rate according to the equationd − A/(GR) +B, whereA andB are constants. It was concluded that long fibres of the desired diameter are obtained by controlling both the freezing rate and the temperature gradient. These results were interpreted in terms of cellular growth of ice crystals.

The outline of the sol-gel method for producing glasses and related materials has been described. This method makes it possible to synthesize glasses at relatively low temperatures and also prepare new glasses which could not be prepared by conventional melting techniques. Thus, this method has a great potential in applications to the synthesis of high technology materials.

The distribution of Ag + ions in the Ag 2 OB 2 O 3 and Na 2 OAg 2 OB 2 O 3 glasses was investigated by X-ray diffraction on the basis of electron radial distribution (ERD) analysis. There appeared peaks at about 3.5 and 6.5 A in the ERD curves of both glasses, which were ascribed to Ag + Ag + distances. It was suggested that Ag + ions formed pairs or clusters in both glasses. The distribution of Ag + ions in Na 2 OAg 2 OB 2 O 3 glasses was considered to be somewhat different from that in Ag 2 OB 2 O 3 glasses at higher concentrations of Ag 2 O.

The vibrational spectra related to the SiO 4 units have been non-empirically calculated, in order to simulate the effect of incorporation of non-bridging oxygens into silica network. Harmonic frequencies and force constants have been calculated for the silicate anion model clusters in silica, disilicate, metasilicate, pyrosilicate and orthosilicate composition by ab initio molecular orbital method using STO-3G basis set at Hartree-Fock SCF level. The calculation showed that the totally symmetric Si-O stretching vibrations of SiO 4 tetrahedra shifted to lower wavenumbers with increasing number of nonbridging oxygens.

In order to understand better the hydrolysis-polycondensation of Si(OC 2 H 5 ) 4 having four functional groups, the corresponding reaction of (CH 3 )Si(OC 2 H 5 ) 3 and (CH 3 ) 2 Si(OC 2 H 5 ) 2 having three and two functional groups, respectively, has been investigated. The tri-functional silane exhibited a similar polycondensation behavior to that of tetra-functional silane; the uniform solution increased in viscosity with time, finally gelling. Fibers could be drawn from the solution before gelation. On the other hand, the bi-functional silane was phase-separated at a certain stage of polycondensation, and no gelation was found over a reasonable time period, probably due to ring molecule formation. On the basis of these data, discussion is presented on the nature of polymers found in the spinnable solution.

The SiKβ fluorescence X-ray and infra-red absorption spectra of Na2O-TiO2-SiO2 and K2O-TiO2-SiO2 glasses have been measured in order to study the Si-O bonding as a function of the composition of glass. The chemical shifts of the SiKβ peak relative to that of silica glass [Δλ=λ(SiO2)-λ(specimen)>0] and the wavenumbers of the infra-red absorption peaks around 950cm−1 and 1100 cm−1 have been determined from the spectra. The SiKβ chemical shift in both series of glasses increased with increasing total content of R2O and TiO2 and with decreasing ratio of TiO2/(K2O+TiO2), where R2O represents Na2O or K2O. The infra-red peaks around 950 cm−1 and 1100 cm−1 shifted towards lower wavenumbers with increasing total content of R2O and TiO2 and with decreasing ratio of TiO2/(R2O+TiO2). These experimental facts were interpreted as showing that the Si-O bond in glass was weakened as the total content of R2O and TiO2 increased and that the Si-O bond was weakened by R2O more than by TiO2.

ゾル.ゲル法によりアンチモンをドーピングしたTiO2薄膜を調製し,その光電気化学的性質を調べた。ESCAにより調ぺた結果,600℃で20分間熱処理したTiO2(アナタース)中のアンチモンはSb3+として存在することがわかった。Sb3+はTiO2中に侵入型で固溶してTio2の電気伝導度を増加させるが,その固溶度限は約1mol%である。光電流は薄膜の電気伝導度の増加の結果として0.5mol%Sb2O3,で約26mA.cm-2となり,若干増加するが,それ以上ドーピングするとかえっでいちじるしく低下し,とくに5mol%Sb2O3では約3mA.cm-2と約1/10に減少した。これはSb3+がTiO2のバンドギャップ中に不純物準位を形成し,それが再結合中心として働くためであると考えられる。TiO2中のSb2O3は光照射下で溶解し,ドーピング種としては好ましくないという結果を得た。

The preparation of superconducting YBa2Cu3O2y through sol-gel method was performed using an acetate aqueous solution. Conditions of gelation and conversion of gel to YBa2Cu3O2y ceramics were investigated, applying thermal analysis, infrared absorption spectroscopy and X-ray diffraction techniques. Transparent gel was obtained from the acetate solution with cation mole ratio of Y:Ba:Cu=1:2:3 by adjusting the initial pH of the solution. Formation of Cu metal, Cu2O and BaCO3 below 400°C was found to occur during heat treatment of the gel. Above 600°C the heated sample turned into a mixture of Y2O3, BaCO3 and CuO, which finally transformed into the single phase of YBa2Cu3O2y at 910°C. The resultant material showed good high Tc superconductivity.

The structure of Na2OGeO2 melts in the temperature range from 1100 to 1150°C has been investigated with the high temperature X-ray diffraction technique. Comparing the radial distribution functions obtained for the melts with those for the corresponding glasses, the first peak due to the GeO interatomic distance is invariant upon melting, although it becomes broader due to thermal vibration. The second peak for the GeGe interatomic distance for melts shifts toward the large distance, which is explained by broadening of the GeOGe bond angle, not by the thermal expansion of the GeOGe bond. The composition dependences of GeO distances and coordination numbers of the Ge4+ ion of the melts are found to be almost the same as the corresponding glasses, indicating that even in melts at such high temperatures 6-fold coordinated Ge4+ ions are present and their content changes with the Na2O content as in the case of the corresponding glasses.

Trimethylsilylation was applied to the hydrolysed and polycondensed products of methyltriethoxysilane in an aqueous solution containing sodium ions. Five trimethylsilylated derivatives of methylsilsesquioxanes present in the solution were detected by gas chromatography and identified by combined gas chromatograph-mass spectrometry.