The dried silica gel monolith with micropores of about 160Å in the average diameter, prepared by the sol-gel method from the Si(OCH₃)₄-H₂O-CH₃OH-(CH₃)₂NCHO-NH₄OH solution, has been tested for the crack formation on immersion in water after heating to various temperatures up to 1030°C. A few cracks occurred in as-dried gel before heating, while severe fine cracks were observed in the gels heated to 500° or 700°C. A rise in heating temperature up to 850° or 900°C resulted in gels with no cracks, while a few cracks occurred on heating to 1000° or 1020°C. No crack was observed when the gel was converted to glass with no open pores by heating to 1030°C. The occurrence and the degree of severity of crack formation have been discussed on the basis of the change of the size of fine pores, and the strength of silica skeleton with heating temperature.

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Silica glass fibers were prepared from mixed solutions of tetraethylorthosilicate (TEOS) and hexamethyldisiloxane (HMDS). An addition of HMDS improves spinnability since the increase in the viscosity of spinnable solutions becomes moderate and the range of the amount of added water for the occurrence of spinnability is widened. Spinnable solutions are obtained when the ratio of silicon in HMDS to total silicon, r, ranges from 0 to 0.6. It is assumed that the fibers drawn from this system consist of linear polymeric particles with double or triple siloxane chains capped with trimethylsilyl groups. Gel fibers from the solutions of r≤0.5 were converted to visually colorless and transparent silica glass fibers by rapidly heating them at 600°C.

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As a first step to prepare flexible amorphous materials, organic-inorganic composite gels in the TEOS-PEG system were synthesized from tetraethyl-orthosilicate (TEOS) and polyethylene glycol (PEG) by the sol-gel method. Gels were obtained in a composition range TEOS=20-100mol% at 50°C with an HCl catalyst. Cracks developed in the TEOS-PEG gels under heat-treatment at 50°-150°C. Density evolution of the gels was measured by the Archimedean method as functions of drying time and PEG concentration. The TEOS-PEG gel showed a maximum density at a composition of 10mol% PEG. DTA and TGA data showed that burn out reactions of the organic materials (alcohols and PEG) in the gels take place in a temperature range of 180°-300°C. The Vickers hardness of the gel showed a decrease with PEG addition. Some of the gels containing a high percentage of PEG exhibited an indent recovery which indicates a flexibility in the gel.

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A hydrolysis-condensation reaction of Al-O-Si alkoxide complex was analyzed by in both the mass fractal dimension and the Guinier radius in small angle X-ray scattering curves. The Al-O-Si alkoxide which was synthesized by reacting Al(OC₄H₉)₃ with hydrolyzed Si(OC₂H₅)₄ consisted of chain-like polymers. When metal alkoxide was hydrolyzed with 0.0082mol of HCl or NH₄OH per 1mol metal alkoxide, both the mass fractal dimension and the Guinier radius increased in proportion to an increase in the water content, and reached 2.5 and 80Å, respectively, at 4mol water per 1mol metal alkoxide. Under the HCl catalyst, both the mass fractal dimension and the Guinier radius decreased up to 1.8 and 20Å, respectively, with increasing HCl concentration, indicating that the three-dimensional branched polymers disaggregated into the chain-like polymers. On the other hand, under the NH₄OH catalyst, both the mass fractal dimension and the Guinier radius showed the fixed values of 2.5 and 80Å, respectively, irrespective of NH₄OH concentration.

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The Al₂O₃-SiO₂ glasses and ceramics has been worthy of remark as high temperature materials. However, the preparation of these glasses are actually impossible by conventional method of melting. This investigation is concerned with the preparation of dense bulk glasses in Al₂O₃-SiO₂ system by the gel process and their thermal expansion as a function of glass composition. The composition studied were xAl₂O₃⋅(100-x) SiO₂ where x=10-90mol% Al₂O₃. The Al₂O₃-SiO₂ glasses of the dense bulk were obtained at 800°C by the gel process. The optimum condition for the preparation of dense bulk glasses was as following; the aluminum nitrate and TEOS were used as raw material and ethylene glycol was used as solvent, The thermal expansion coefficients show the values of 0.5 to 7.5×10^-6K^-1 and increased linearly with increasing Al₂O₃ content. Their expansion coefficients were controllable by changing the composition.

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The effect of parameters involved in the sol-gel preparation of the monolithic porous ZrO₂-SiO₂ glasses on the pore characteristics has been investigated. Followings have been obtained.
(1) A high hydrolysis temperature seemed to be favored to form large micropores in the resultant glasses.
(2) The surface area (SSA), pore volume (PV) are decreased by increasing heating temperature, while mean pore radius (MPR) remained almost unchanged.
(3) The influence of the content of HCl used as a catalyst was most remarkable. As the HCl content becomes higher, the larger MPR resulted.
On the basis of above results, the porous monolithic ZrO₂-SiO₂ glasses containing ZrO₂ up to 14.4mol% have been made via sol-gel reaction at 80°C using h-value as high as 0.5, i-C₃H₇OH as a solvent. The pore size as large as 40-60Å in diameter, SSA and PV ranging from 450 to 550m²g^-1 and 0.4 to 0.7ml·g^-1, respectively, have been attained. Those glasses are highly alkaline-resistant compared to the porous SiO₂ glass.

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V₂O₅ gels were prepared from VO(OR)₃ through hydrolysis in ROH solutions (R=C₂H₅, iso-C₃H₇ and n-C₄H₉). Monolithic red-brown gels were obtained with no catalysts or with acidic catalysts. Syneresis was observed for the gels prepared with acidic catalysts. The color of the gels changed from red-brown to green during aging due to reduction of V⁵⁺ ion to V⁴⁺ ion. The rate of hydrolysis decreased in the order; C₂H₅>n-C₄H₉>iso-C₃H₇. The gel formation reaction is considered to be 2 VO(OR)₃+(3+n+x/2)H₂O→H_xV₂O₅⋅nH₂O+6ROH+(x/4)O₂, accompanying the reduction of V⁵⁺ ion to V⁴⁺ ion. The gels can be described as HxV2O5⋅nH₂O, and they seem to have a vanadium bronze-like structure. X-ray diffraction measurements of the pulverized gels indicate that the gels have a 3-dimensionally ordered structure.

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Glass-ceramics that are useful for castable dental crown were searched for in the systems based on 3CaO⋅P₂O₅, MgO⋅TiO₂ and CaO⋅MgO⋅2SiO₂ (see Fig. 1 and Table 1). A glass composed of MgO 16.9, CaO 24.8, SiO2 16.3, TiO₂ 22.8, P₂O₅ 15.7, CaF₂ 2.0, Al₂O₃ 1.0, ZrO₂ 0.5, and MnO 0.01wt% which was melted at 1350°C could be shaped into a dental crown free from any defect, such as pores, devitrification products and chemical reaction products with a mold, by a conventional lost-wax process using a centrifugal casting machine (see Fig. 2). The glass in the shape of a dental crown was converted into a glass-ceramic similar to natural teeth in color and translucency without any deformation by heat treatment up to 940°C (see Figs. 3 and 4). The glass-ceramic contained crystalline apatite and magnesium titanate in fine grains (see Figs. 5 and 6). It was confirmed to accurately reproduce the original wax pattern (see Fig. 4). The glass-ceramic showed a density and thermal expansion coefficient similar to natural teeth; and the mechanical strength, Young's modulus and hardness were higher than those of the natural teeth. It also possessed excellent fracture toughness and chemical durability (see Table 2).

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Porous glass specimens were prepared from a fluorine-containing borosilicate glass and were chemically treated up to ten times repeatedly. During the treatment, the hydrogen fluoride which was generated by the reaction between ammonium fluoride and sulfuric acid in the open pores was allowed to react with the porous glass specimen. The untreated porous glass had the porosity of 28%, the pore volume of 0.179ml/g, and the surface area of 22m²/g. After treated ten times, the porosity and the pore volume increased to 37% and 0.268ml/g, respectively, while the surface area remained almost unchanged. The nitrogen adsorption and Hg intrusion measurements revealed that there exist pores having the diameter of 10-50Å and 300-600Å in the untreated porous glass. The pores having the diameter of 10-30Å completely disappeared after two times of the treatment, which was attributed to the removal of colloidal silica precipitated in the larger pores during the preparation process of porous glass. On the other hand, through the repeated treatments, the amount of pores of 30-300Å and 400-700Å relatively increased, while that of pores of 300-400Å decreased. This change was considered to result from further dissolution of the pore surface. Consequently, the liquid permeability in the porous glass was found to increase considerably by the chemical treatment described above.

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We prepared many bulk glasses in compositions around BiSrCaCu₂O_x using the conventional melt quenching method and examined superconducting properties of the glass ceramics obtained. It was found that the compositions in the Bi-Sr-Ca-Cu-O system had a great tendency to form a glass and Bi₂O₃ played an important role in the glass formation. The glass transition and crystallization temperatures for the glasses of Bi_xSrCaCu₂O_w (x=1.2-3) were in the range between 425° and 370°C and in the range between 450° and 430°C, respectively and both values tended to decrease with increasing Bi₂O₃ content. The ratio of SrO and CaO was also important for the glass formation and the coexistence of SrO and CaO was needed to form a glass. Many glasses became superconducting glass ceramics with the T_c values of around 75K by annealing at 820°C for 40h air.

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High-strength bioactive glass-ceramics were prepared by hot-pressing the mixtures of glass and tetragonal zirconia polycrystal (TZP) powders at 1150°-1200°C for 2h under the pressure of 30MPa. Mechanical properties of bioactive glass-ceramics were much improved by dispersing TZP powders sintered at 1400°C (TZ) or specially prepared for low temperature sintering (NSZ). The bending strength of the composite containing 40vol% TZ and NSZ showed 600MPa and 900MPa, respectively. The bending strength of the composite toughened by TZ increased with increasing TZ content up to 60vol% showing maximum value of 800MPa, and then decreased over 70vol%. On the other hand, the bending strength of the composite toughened by NSZ increased monotonously with increasing NSZ in whole range. Many defects were found in the specimens containing TZ over 70% by SEM observation and were considered to degrade the bending strength. The number of the points which zirconia grains contact directly with each other may increase with the increase in zirconia content. The defects were formed at these points because TZ powder did not sinter sufficiently at 1200°C. The composite containing 40vol% TZP still maintained high bioactivity though the bioactivity of the composite containing more than 50vol% TZP was poor. The bioactivity was evaluated from apatite formation on the surface in a simulated body fluid at 37°C for 30 days.

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In Raman spectra of ZnBr₂-KBr-PbBr₂ glasses, the dominant bands are observed at about 60cm^-1 and 155cm^-1 or 174cm^-1. The 60cm^-1 band was assigned to the mode containing bending vibrations and the 155cm^-1 or 174cm^-1 band to the symmetric mode containing the stretching vibration between zinc and bridging or non-bridging bromine, respectively. The compositional dependence of the intensity of the 155cm^-1 and 174cm^-1 bands gives information about both the structural role of PbBr₂ and the network structure from the viewpoint of bridging and non-bridging bromines. The introduction of PbBr₂ increased the number of non-bridging bromine. This indicates that PbBr₂ has the same role of glass modifier as that of KBr. On the other hand, the 155cm^-1 band was observed even for a glass of the composition with 20mol% PbBr₂, in which the atomic ratio, Br/Zn, is 4. This suggests that there are free bromide ions and/or zinc ions coordinated with more than four bromide ions.

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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.

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Barium borophosphate glasses of composition BaO⋅2(1-x)B₂O₃⋅2xP₂O₅ have been prepared and their constitution of network has been discussed on the basis of composition dependence of the molar volume, elastic constants and Raman spectra which are compared with those of the potassium glasses. The trend of variation of the molar volume and elastic constants for the barium glass is similar to that of the potassium glass: the molar volume increases with increase in x with a plateau near x=0.5 in the volume vs. x curve, at which value of x the elasticity reaches a maximum. This shows apparent similarity in constitution of the barium glasses to the potassium ones. From the log-log plot of bulk modulus vs. mean atom-pair volume for both systems it is concluded that the higher elasticity of the barium glass than the potassium one is due to the stronger interaction of barium cations with their environment. Raman spectra for the barium glasses with smaller x have a band due to boroxol groups, showing elimination of Ba²⁺ ions from BO₄^- units accompanying decomposition of borate rings with a BO₄^- unit. This indicates that the distribution of BaO to B₂O₃ and P₂O₅ in proportion to their mixing ratio is not likely to occur in the barium borophosphate glasses and more BaO is distributed to P₂O₅ than expected from the mixing ratio.

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Amorphous films in the system of AlPO₄-Al₂O₃ were prepared by rf sputtering, and their physical properties such as density, refractive index and thermal expansion coefficient, and the infrared absorption spectra were measured. The physical properties and the infrared absorption spectrum of an amorphous AlPO₄ were very similar to those of SiO₂ glass. All the physical properties of the amorphous AlPO₄-Al₂O₃ films had the same compositional dependence; that is, they increased linearly with increasing Al₂O₃ content up to about 80mol% Al₂O₃, beyond which they increased more rapidly. The results of infrared spectra indicated that the coordination number of aluminum ions was 4 below about 80mol% Al₂O₃ content, but increased rapidly to about 5 above 80mol% Al₂O₃, reaching to the value of an amorphous Al₂O₃ film.

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⁵⁷Fe-Mössbauer measurements of semiconducting silver vanadate glasses were performed at temperatures ranging from 78 to 298K. It proved that Fe³⁺ ions, incorporated into the vanadate glasses as a Mössbauer probe, are present at substitutional sites of tetrahedral V⁵⁺ or V⁴⁺ ions. Absorption area vs. temperature plot for 5Ag₂O⋅85V₂O₅⋅10Fe₂O₃ and 45Ag₂O⋅45V₂O₅⋅10Fe₂O₃ glasses gives two straight lines with different slopes, which correspond to the Debye temperatures of 344 and 279K. These results indicate that an introduction of Ag₂O into V₂O₅ matrix results in a gradual change of the glass matrix from a two-dimensional layer structure, originally composed of VO₅ tetragonal pyramids, to a chain structure composed of VO₄ tetrahedra. It is concluded that glass matrix of silver vanadate glasses is essentially the same as that of alkali (Li, Na and K) vanadate glasses. Silver vanadate glasses will have fewer nonbridging oxygen (NBO) atoms than alkali vanadate glasses.

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The glass-forming regions in the ternary systems LiX (X=F and Br)-Li₂O-TeO₂ were established in the present study. For X=Br the glass-forming region was found to be widened up to about 75mol% LiBr on the LiBr rich side compared to the system containing LiCl which was studied previously, while the region for X=F was restricted to the Li₂O side, and no glass was formed in the binary LiF-TeO₂ system. These results were interpreted based on the glass structure which was mainly deduced from the IR measurement.

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The electron irradiation induced crystalline to amorphous (C-A) transition was examined in the Ni-B binary system by ultra-high voltage electron microscopy. The seven equilibrium phases (i.e., Ni, Ni³B, Ni²B, o-Ni⁴B³, m-Ni⁴B³, NiB, and B) in the system were all irradiated with 2MeV electrons at a fixed temperature of 4.2K, and the tendency towards the C-A transition has been compared among the phases. Of the seven, only Ni²B and o-Ni⁴B³ compounds undergo a complete C-A transition by the irradiation while the other five do not. Analysis of the results shows that the amorphization tendency under electron irradiation is best correlated with the position of the materials in the corresponding temperature-composition phase diagram. Namely, those compounds whose position in the diagram is close to the bottom of a deep valley of liquidus in the diagram have a strong tendency towards the C-A transition, while those away from such a valley do not exhibit the C-A transition.

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Amorphous-forming ability in the pseudobinary Al₂O₃-ZrO₂ system by liquid quenching has been examined over the wide composition range from 25wt% ZrO₂ to 65wt% ZrO₂ in Al₂O₃, using an Xe arc lamp imaging furnace combined with a twin-roll type quenching apparatus. It becomes evident through TEM studies that amorphous materials can be produced in the composition region ranging from 30wt% ZrO₂ to 60wt% ZrO₂. Furthermore, studies on the crystallization behaviors of the amorphous materials have revealed that the amorphous ceramics with the eutectic composition has a crystallization temperature of 1213K, which is the highest among the amorphous ceramics with compositions deviating either positively or negatively from the eutectic. This indicates that the crystallization temperature becomes high with increasing ease of amorphization. This observation is of significance in revealing the nature of atomic bonding in amorphous materials.

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In order to clarify the crystallization mechanism of glass phase in glass/ceramic composites, relations between crystallization behaviour and the particle size of borosilicate glass were investigated. Further by changing alumina content of the glass/ceramic composites, the effects of alumina on crystallization of glass in glass/ceramic composite were discussed. The crystallization of borosilicate glass powders depend on particle size and cristobalite crystals are formed in the glass powders of less than 5mm diameter. The glass/ceramic composites containing 25wt% alumina do not show any crystallization tendencies and have thermal expansion coefficient (TEC) close to that of Si single crystal. Al in alumina particles diffuse in glass phase during firing. The Al and Si take places of the network former of glass. Consequently, these changes of composition and viscosity in glass phase is supposed to prevent the crystallization.

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Recently, alumina-borosilicate glass composites have been applied as a substrate material for hybrid IC and LSI multi-chip packaging. In this paper, the effects of the composition of borosilicate glasses on the properties and the microstructure of alumina-borosilicate glass composites were studied. These composites were divided into the three groups by composition of borosilicate glasses. In the first group, no crystallization is found. In the second group, crystallization of SiO₂ is found. And in the third group, compound by the reaction between alumina and glass is precipitated. It was found that the composites become gradually difficult to densify in the above mentioned order. In the first group, the sintering temperature of the composites has relation to the softening temperature of the glasses. In the composites belonging to the third group, many pores were formed when crystallization occurred. Dielectric constant of the composites depends on the glass compositions, leading to a conclusion that the glass systems with low dielectric constant are desired. On the contrary, thermal expansion coefficient of the composites depends on the crystalline phases, so we need to choose low thermal expansion glasses which do not crystallize or glasses in which crystalline phases of low thermal expansion is precipitated during sintering. It is also important to control the ratio of glass in the composites and the firing conditions.

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The phase transformation behavior of tetragonal zirconia polycrystal (TZP) in high strength bioactive glass-ceramic composite was investigated in hot water. The transformation of TZP from tetragonal to monoclinic phase dispersed in the glassceramic matrix took place at a higher rate than one of the bulk TZP sintered body. It was considered that this acceleration is caused by applied tensile stress in the dispersed TZP particles due to the difference in thermal expansion between the glassceramic matrix and the TZP. The transformed zone size was found to be very small (only about 2μm thick) by laser raman spectroscopic analysis. It was certificated that the progress of the transformation was restricted by the formation of an apatite layer on the surface of the composite during the long-term soaking test because of its bioactivity. It was found that the phase transformation of TZP dispersed in the glass-ceramics could be restricted remarkably by means of (1) matching the thermal expansion of TZP and glass-ceramic matrix, and (2) using TZP of almost perfect density and of very fine crystal grain size.

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To fabricate glass-ceramics for uses in electronic devices such as multilayer packages for VLSI chips by firing below 1000°C, the compositional range of the glass formation and the precipitation of crystals in the system MgO-Al₂O₃-SiO₂ were investigated. The compositional range which the melts below 1600°C were quenched into water to form the glasses, was determined. A tendency towards expansion beyond the compositional range reported by other workers was recognized in the present work. The single, binary and ternary compounds such as enstatite, spinel or cordierite in the system crystallized in the melts quenched to form the glasses. The metastable phase such as μ-cordierite or MgO⋅Al₂O₃⋅4SiO₂, which can never be developed by solid reaction or crystallization of melts during cooling, precipitated in some glasses. The well sintered glass-ceramics were obtained from glass-compacts with the compositions of 10-35wt% MgO, 10-35wt% Al₂O₃ and 45-65wt% SiO₂ by firing below 1000°C.

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In a relatively wide region of the pseudoternary system BiO_3/2-(CaO⋅SrO)_1/2-CuO, CaO/SrO=1, glassy samples have been obtained by the rapid-quenching technique. The glass transition temperature in this system was found to be mainly dependent on the BiO_3/2 content, with a maximum of 390°C at around 20mol% BiO_3/2. The crystallization of the glasses of proper compositions such as BiCaSrCu₂O_x and Bi₂Ca₂Sr₂Cu₃O_x produced superconductors consisting mainly of the low-T_c (80K) phase; this superconducting phase grew gradually with increasing heat-treatment temperature. The critical temperature T_c (zero) was 86K for Bi₂Ca₂Sr₂Cu₃O_x, whereas it can be expected to be increased by optimizing the heat-treatment conditions and/or using appropriate additives.

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Microstructural changes of amorphous Si-N-C fine powders were studied by X-ray diffraction, transmission electron microscopy, IR spectroscopy and chemical analysis. The samples examined had varying contents of Si, N and C (C5: Si-35.8N-4.8C, C8: Si-32.8N-8.1C, C17: Si-29.0N-17.3C, C20: Si-24.2N-19.7C), and were prepared by pyrolysis of hexamethyldisilazane ((Me₃Si)₂NH, Me=CH₃). These samples were heat-treated in an argon atmosphere at 1743 and 1803K for periods of up to 64.8ks. X-ray diffraction showed that the crystallized phase consisted mainly of α-Si₃N₄ and β-SiC. In the C5 and C8 powders, the size of crystallized β-SiC was 20-100nm under all heat treatment conditions, and β-SiC in C17 and C20 powders grew 50-1500nm and 20-200nm in size respectively, after heat treatment at 1803K for 64.8ks. The morphology of α-Si₃N₄ in C5 and C8 powders was rod-shaped, and the size of the α-Si₃N₄ was larger than that of β-SiC. On the other hand, the fine-grained and the thin-plated α-Si₃N₄ were observed in all of the samples heat-treated for 64.8ks at 1803K. We believe that the formation of fine-grained and thin-plated α-Si₃N₄ relate to the development of mechanical properties of Si₃N₄-SiC composites.

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The optical absorption edge of the as-sputtered amorphous red phosphorus (a-p_red) film was found to be shifted considerably to a shorter wavelength by Xe-light illumination. On prolonged illumination the film finally vanished away. The photobleaching rate decreased with decreasing temperature.
The photobleaching rate at room temperature was 10⁷-10⁸ times as high as that of thermal bleaching without illumination. This photobleaching rate also increased with increasing oxygen partial pressure in the atmosphere. It was reasonable to conclude that this irreversible photobleaching in a-P_red film consists of two stages; in the first stage, rapid photobleaching takes place, during which the film thickness remains constant and a new transparent layer is produced on the surface of the a-P_red film. In the second stage, the photobleaching rate is slower compared with that of the first stage; photo-enhanced evaporation from the film surface occurs during this stage, where photobleaching is due to the decrease of the film thickness. This situation was the same regardless of oxygen partial pressure.

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Photobleaching mechanism for amorphous red phosphorus film was discussed from the XPS results obtained here and the phenomenological results reported in part I. XPS spectra of the photobleached film gave two peaks in P-2p; one peak, which appears in the as-sputtered film, is due to P-P bonding, and another peak appearing on illumination is to P-O bonding. Photobleaching observed in this experiment was found to be induced by photo oxidation. Band gap illumination excites the σ-bonding electrons forming P-P bonds. A part of the excited P-P bonds dissociates and reacts with diffusing oxygen from atmosphere to form P-O bonds. The mechanism was considered to be composed of following two stages. In the first stage, a thin layer of phosphorus oxides forms on the surface of the film. The rate of this photo oxidation is controlled by the diffusion of oxygen from atmosphere. A simple experimental relationship between the decrease of the optical film thickness (Δd_op) and the illumination time (t), Δd_op∝t^1/2, is obtained. Although the decrease of the optical thickness is observed in this stage, the film thickness (d) remains unchanged. In the second stage, photobleaching is due to the decrease in the film thickness, which is caused by evaporation of oxide layer; the decreasing rate of d is equal to that of d_op.

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The results of this investigation were: (1) Amorphous PMW was obtained by a rapid quenching method using a twin-roller apparatus. (2) The dielectric constants of quenched PMW showed a peak at 650K. This could be explained by ionic conductivity change due to its glass transition and crystallization process. (3) Three crystalline phases (Pb(Mg_1/2W_1/2)O₃, PbWO₄, Pb₂WO₅) were found when the quenched PMW was heated above the crystallization temperature. (4) The dielectric constants of annealed PMW showed a peak at 283K. This was attributed to a phase transition in the precipitated perovskite phase, though the transition temperature was 30K below that of sintered PMW.

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The heat capacity of several sodium silicate, borate and germanate oxide glasses were measured at low temperatures. The experimental results of these glasses were analyzed, using the three-band theory postulated by the present authors. The characteristic temperatures (θ₁, θ₃, θ_E) obtained were used to determine the chemical bonds of atomic and molecular interactions in the glasses. The compositional variation in θ₁ and θ_E depended on the type and amount of cations incorporated, which agreed with the infrared spectra.

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The dissolution behavior of silicate glasses was studied as a function of compressive stress and time. The two-dimensional compressive stress on glass surface was introduced by utilizing the difference of thermal expansion coefficients between glass and ceramic substrate. The release rates of Na⁺ ions from these glasses into distilled water were determined by using atomic absorption analysis. As a result, the release rates of Na⁺ ions increased along with an increase of compressive stress in both diffusion and reaction stage, that is contrary to the general concept that compressive stress reduces the diffusion rate because of a decrease in void volume. In order to explain this behavior, the new hydrolysis mechanism under compressive stress was suggested. FTIR measurements were also carried out to support this mechanism.

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The heat of crystallization (ΔH) for rapid quenching materials was measured to establish the non-crystallinity under several cooling rates. The values of ΔH were increased by increasing the cooling rate, and at the glassy states, these values reached to the constant value (ΔH₀). The value of ΔH/ΔH₀ was proposed to provide the experimental parameter of non-crystallinity normalized from crystalline (=zero) to glass (=unity). The physical properties, for example, the coercive forces of BaO-Fe₂O₃, the Vickers hardness and electrical resisitivity of Pd₈₂Si₁₈ and Ni₆₇Si₁₃B₂₀, were related to the non-crystallinity (=ΔH/ΔH₀). This experimental parameter was useful to understand the state of the non-crystalline solid which had diffused pattern in X-ray diffraction.

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Phase separation in Li-Si-O-N oxynitride glasses has been studied in terms of the effect of nitrogen on the miscibility. Substitution of nitrogen for a part of oxygen lowers the miscibility temperature linearly with an increase in the nitrogen content. An oxynitride glass with ca. 10eq% nitrogen shows a lower miscibility temperature by about 90K than that of the corresponding oxide glass without nitrogen. The decrease in the electrostatic attractive force between lithium and the network anions caused by the covalency of nitrogen may be responsible for an increase in the miscibility.

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Total electrical conductivity depends on both the content of cuprous ions and of the halide ions in the glass.
Considerably large electronic conductivity of the glasses suggests that hopping conduction between Cu⁺ and Cu²⁺ is likely to occur. Contribution of the halide ions to the electrical conductivity can be explained that they drastically increases the mobility of carrier, both ionic and electronic ones.
It is suggested from IR spectra that the structure of glasses consists mainly of metaphosphate chains.
The halide anions remaining outside the phosphate chain will enhance the movements of the carrier by forming the pair of Cu⁺ ion with them.

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X-ray irradiation was applied to mixed alkali silicate and sodium borosilicate glasses. In the former glasses, the energy of visible absorption due to non-bridging oxygen hole centers decreased along with the increase of average basicity of the glasses. This is related to weakning of the Si-O bonding with the presence of the alkali metal cations. In the sodium borosilicate glasses, the induced absorption due to Si-O-Na linkage appeared only in the concentration range of [Na₂O]/[B₂O₃]>1; thus the peculiarity of the microstructure of sodium borosilicate glass, such as phase separation was also reflected to the irradiation phenomena. From the thermal bleaching of the irradiated glasses, the relative stability of the defect centers could be differenciated.

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Mullite was synthesized by a sol-gel method from the mixed solutions of Si(OC₂H₅)₄ and Al(NO₃)₃ with small amounts of the mineralizing additives such as MnCl₂, Fe(NO₃)₃, CoCl₂, Ni(NO₃)₂ or CuCl₂. The formation of mullite began at about 1100°C for the sample with 3.73×10^-3mol (R_Cu=3.74×10^-2) CuCl₂⋅2H₂O. The accelerating effect of mullite formation was observed for all samples with mineralizing additives except those with more than 3.64×10^-3mol (R_Mn=2.94×10^-2) MnCl₂⋅4H₂O and, with less than 1.61×10^-3mol (R_Fe=1.44×10^-2) Fe(NO₃)₃⋅9H₂O and 1.78×10^-3mol (R_Co=1.23×10^-2) CoCl₂⋅6H₂O. Ni(NO₃)₂ was most effective for the accelerating of mullite formation among the mineralizing additives.

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Highly transparent amorphous thin films of Al₂O₃ were prepared by adding some chelating agents such as β-diketones to the Al-alkoxide/alcohol starting solutions. Among the β-diketones examined, ethylacetoacetate was the most effective in stabilizing the alkoxides against water, because of the formation of an Alchelate complex. The Al₂O₃ films obtained were amorphous and transparent below 700°C, whereas they crystallized in γ-Al₂O₃ at 900°C, which transformed to α-Al₂O₃ at 1000°C, accompanying the loss of transparency.

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Vanadate glass is well known to be semiconducting with small polaron hopping. Dc conductivity at a high temperature, σ, becomes maximum at c_V=[V⁴⁺]/[V_total]≈0.5 when [V₂O₅]≤30mol%, but at c_V≈0.1-0.2 when [V₂O₅]≥50mol%. The mean V⁴⁺ ion spacing, a_V⁴⁺, when σ is maximum, is almost constant, about 0.8nm, in the range where [V₂O₅] is more than 10mol%. On the other hand, HFS of ESR spectra of these glasses are not observed when a_V⁴⁺≤0.8nm, i.e. c_V is more than 0.1-0.2 when [V₂O₅]≤50mol%, because of the interaction between V⁴⁺ ions. It is suggested that mobility of small polaron is decreased by the interaction between V⁴⁺ ions when a_V⁴⁺ is less than about 0.8nm.

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Electrical resistivity at 30° to 60°C, current-voltage characteristics and thermal response by chopped light were measured for SiC fibers (Nicalon). The SiC fibers showed NTC resistance-temperature characteristics, and thermistor constant B was 20 to 4640K. Current was proportional to applied voltage under an applied electric power below 4mW (for 500 fibers with 10 mmlong). A well-defined resistance change of SiC fiber (B=2920K) was observed under a cyclic temperature change in 20Hz by chopped light. The SiC fiber was found to be a promising material for thermistor with a fast thermal response.

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