From a viewpoint of the treatment of high level radioactive liquid wastes, the immobilization of some rare-earth metal ions; La, Ce, Nd, Sm and Gd; from aqueous solutions was studied by the use of the hydrated titania (H₂Ti₂O₅⋅nH₂O) fibers as a cation adsorbent. The saturated uptake of each metal ion was in a range of 1.73 to 2.72meq·g^-1. The adsorbed metal ions were immobilized in crystal lattices as main components of various titanates after sintering. The La and Nd ions were immobilized into a mineral assemblage consisting of rutile and La₄Ti₉O₂₄ or Nd₄Ti₉O₂₄. The Sm and Gd ions were also immobilized into a mineral assemblage of rutile and Sm₂Ti₂O₇ or Gd₂Ti₂O₇. The Ce ion did not react with the adsorbent to make titanate at temperatures below 1250°C, and was immobilized into a mineral assemblage of rutile, CeTi₂O₆ and CeO₂ at 1300°C. The leachabilities of rare-earth metal ions in these immobilizers were measured at 25°C under normal atmospheric conditions using distilled water. The results indicated that these immobilizers are very stable with the maximum 5.1×10^-9g·cm^-2·d^-1.

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The Vickers hardness of α-Si₃N₄ is higher than that of β-Si₃N₄. The erosive wear caused by solid particle impingement was tested for a series of hot pressed Si₃N₄ ceramics with different phase contents of Si₃N₄. The anti-erosive wear property of Si₃N₄ including α-phase was inferior to that of 100% β-Si₃N₄. The poor anti-erosive wear of Si₃N₄ including α-phase is due to its low fracture toughness (K_c) in spite of its high hardness (H). The erosion rate (V) of hot pressed Si₃N₄ is related to H and K_c by the equation V=e^8.76H^-0.27K_c^-7.1, derived from multiple regression analysis.

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The rotary bending test was carried out on sintered Si₃N₄ at room temperature in the range from 10⁴ to 10⁹ stress-cycles with an Ono's rotary bending fatigue testing machine operating at 3400 cycles per minute. Mirror-like regions were observed on the fracture surfaces after the test. The mirror-like region was roughly semicircular, and the fracture propagated radially from the mirror-like region. The size of mirror-like region was determined from optical micrographs at a magnification of 25. The size of mirror-like region was correlated with the stress amplitude and the number of cycles to failure. The failure was shown to occur when stress intensity factor at the deepest point of the mirror-like region reached fracture toughness of the material. It was considered that the mirror-like region was restricted to the subcritical crack growth under the cyclic stress, and the failure occurred when its size reached a critical value which is dependent on the stress amplitude.

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Young's modulus and internal friction of engineering ceramics such as silicon nitride, silicon carbide and tetragonal zirconia polycrystals were measured by the resonance method up to 1400°C. Effect of hanging position on the apparent value of Young's modulus and internal friction was investigated. The apparent value of internal friction increased when the specimen is hung near the edge of the specimen because of the loss of vibration by the equipments. The error of apparent value of internal friction was negligibly small if the shift of hanging position from the node is less than 2.4% of the total length of the specimen. Measured value of Young's modulus was independent of hanging position. Internal friction increased abruptly above 1150°C in hot-pressed silicon nitride, above 1000°C in pressureless sintered silicon nitride and tetragonal zirconia polycrystals with increasing temperature. Internal friction showed peaks at 1080°C in hot-pressed silicon nitride, at 600°C in silicon carbide and at 180°C in tetragonal zirconia polycrystals. All of these temperatures corresponded to the temperatures at which Young's modulus decreased.

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Alpha-Si₃N₄ powder was explosively compacted by one-dimensional shock treatment between 5 and 30GPa shock pressure. The effect of shock pressure on the compact characteristics was examined by observing the relative density, hardness, crystallite size, residual strain in the lattice (XRD), a lone pair electron (LPE) concentration (ESR) and Si solubility in 1N NaOH aqueous solution. The hardness of the compact increased linearly as the shock pressure increased while the relative density was shown to have a maximum. Crystallite size and residual strain in the lattice showed a large pressure dependence from 5-10GPa. The concentration of LPE in the raw material decreased by the shock treatment. The soluble Si in the 1N NaOH solution increased, and the LPE concentration of the shocked sample decreased by the dissolution treatment. The characteristics of shocked compacts were improved by applying the explosive shock treatment method which suppressed the temperature increase.

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The effect of MoO₃ addition on the phase separation of sodium borosilicate glasses has been studied by electron microscopic observation and electrical conductivity measurement. With increasing MoO₃ addition, the immiscibility temperatures rose, the growth rate of phase separation increased, and the immiscibility region in the Na₂O-B₂O₃-SiO₂ system extended. When MoO₃ more than 5mol% was added to the glasses, two stages of phase separation appeared; one is metastable immiscibility, which takes place below the liquidus temperature, and the other is stable immiscibility, occurring above the liquidus temperature. The present experiment confirmed that the conductivity measurement of molten glasses is usefull to detect phase separation in the glasses, giving some suggestions for preventing the separation of molybdates in nuclear waste glasses and also for controlling the micro-pore sizes of porous glasses.

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This report describes the formation of foam glass made from abundant glassy volcanic ashes existing in south Kyusyu (Kagosima-ken), Hokuriku (Ishikawa-ken), and Hokkaido. A specified batch composition in the system volcanic ash, sodalime-silica glass, and sodium silicate (anhyd.), has been calcinated at 900°C for 10 minutes in an electric furnace to obtain foam glass. This experiment has provided various usefull foam glasses with desired quality, for insulating materials (bulk density: 0.23Mg/m³, thermal conductivity: 0.07W/m·K) and inner or/and outer sawing materials (bulk density: 0.65Mg/m³, thermal conductivity: 0.14W/m·K). All volcanic ashes used in this experiment has satisfied requirements for raw materials. When the six definite straight lines are extrapolated to find by plotting the physical properties (bulk density, thermal conductivity, average pore diameter) of foam glass on various amounts of the soda-lime-silica glass at the right-angled coordinates definates x-axis as the amount of sodium silicate (anhyd.) including the glass batch, and y-axis as the physical properties, every lines intersected and converged on one point. When the intersectional coordinates are the bulk density and thermal conductivity of foam glass, all the values of x-axis are the same. And, when the intersectional coordinates are the average pore diameter of foam glass except Sample No. 2, all the values of y-axis are the same. It was found that all the glassy volcanic ashes used in this experiment have essentially the same property ranging from south Kyusyu to Hokkaido.

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Crack initiations in soda-lime silicate glass during Vickers indentation were observed with an optical microscope, and the accompanied acoustic emissions (AE) were measured to evaluate K_IC by the indentation micro-fracture (IM) technique. A large amount of small amplitude AE, which corresponds to the surface cracks, was detected during indentation load increment. When the load exceeded about 10kgf, penny shaped median type cracks initiated accompanied by large amplitude AE, the wave of which was composed of longitudinal wave, the reflection at the side wall of the wave guide and transversal wave. Just before the load reaching zero, lateral type cracks initiated accompanied by the large amplitude AE, in the wave of which clear longitudinal wave could not be observed. When the load was decreased before median crack initiation, the median crack initiated at the load decrement. The amplitude of the longitudinal wave (ξ) increased with increasing maximum indentation load (P). The amplitude increased also proportionaly to the crack length, which means that the energy of AE increases proportionally to the crack area.

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A crystalline zirconium oxide sulfate compound with layer structure was synthesized by hydrothermal treatment of a mixture of zirconium hydroxide and sulfuric acid solution. The formation condition, crystallinity, composition and thermal changes of the compound crystals were investigated. It was found that the zirconium oxide sulfate layer compound is formed at temperatures above 150°C and pH values below 2. The crystallinity of the compound increased with the increase of both H₂SO₄ concentration and heat-treatment temperature. The crystals had a thin platelike shape 200-700nm in diameter and less than 20nm in width, and those synthesized at 220°C were sexangular. An electron diffraction pattern showed that there was a 6-fold symmetry axis in the direction perpendicular to the crystal with the lattice constant a equal to 0.63₂nm obtained by assuming a face of the crystals, and on the assumption of being hexagonal lattice. The ratio Zr: SO₄^2- in the compound with high crystallinity was about three. The compound lost its interlayer water below 600°C, with the layer spacing decreased to a constant value of 1.04₈nm. Then, the compound was desulfurized at about 650°C, resulting in metastable tetragonal or monoclinic ZrO₂ platelike skeletal grains.

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Mixed powders of Al₂O₃ and TiO₂ were prepared by different processes using aluminum sulfate as a starting material of Al₂O₃ source. Aluminum titanate was synthesized by heating the mixtures in the presence of AlF₃. Rod-like grains of Al₂TiO₅ were produced by using mixed powder of γ-Al₂O₃ and anatase (TiO₂). Rod diameter and aspect ratio of Al₂TiO₅ grains depend on the preparation methods of raw materials. One of the best results, in which rod diameter and aspect ratio of the grains was about 5μm and about 4, respectively, was obtained by heating the raw materials prepared by calcination of the coprecipitated hydroxides at 700°C, in the presence of 10% of AlF₃ at 1350°C. The elongated direction of the grain corresponded to a-axis (according to JCPDS card 26-40) of Al₂TiO₅ crystal. A sintered body of highly oriented Al₂TiO₅ crystals, in which Lotgering's index F//a was 0.88, was obtained owing to the anisotropic shape of the Al₂TiO₅ grains.

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Thin film of lithium tantalate was prepared by the dipping process from double alkoxide of the corresponding composition. SEM-observations and the X-ray diffraction analyses showed that the film consists of a pile of micro-particles (200-300Å in diameter), and that the particles are amorphous when baked at 450°C or below and poly-crystalline when baked at 480°C or above. These two phases showed a marked difference in Raman spectra. The amorphous film showed ionic conductivity. Behavior of the amorphous film as a moisture-sensitive device was investigated. Surface ac-resistivity of an element (3.2×3.2mm, 1μm thick with a pair of comb-type electrodes) covered the range 10⁷-10⁴Ω at the relative humidities of 25-90%. Reproducibility of the resistivity in the repeated cycles of the humidity was good, temperature-dependence was small and the response time to an abrupt change of humidity was sufficiently high. It was proved that the amorhous film is highly applicable.

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The electrical resistivity of ZrO₂-12mol% Y₂O₃ single-crystal was measured at temperatures from 700° to 1600°C, using the complex impedance method and d. c. four terminal method. Time dependence of the electrical resistivity appeared at temperatures below 900°C. The temperature dependence of the electrical conductivity was represented by the following equation: σ=A/Texp{-(α+βT^-1)/κT} where A, α and β are constants, and κ is Boltzmann constant. Constants obtained by the least squares method were A=3.455×10⁴Ω^-1cm^-1 K, α=1.864×10^-1eV and β=5.460×10²eVK, respectively.

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The synthesis of thermal-shock-resistant material from KZr₂(PO₄)₃ was investigated. Sintering of KZr₂(PO₄)₃ was promoted by adding a metal oxide such as MgO. Thermal expansion coefficients of KZr₂(PO₄)₃ crystal are α_a=-4.4×10^-6/°C, α_c=7.6×10^-6/°C, and α_avg.=-0.4×10^-6/°C, respectively. The linear thermal expansion coefficient of the sintered ceramic was near zero. The maximum strength of this ceramic was about 150MPa after quenching into water from 1300°C. In addition, the dense strong low-thermal-expansion ceramic in the system KZr₂(PO₄)₃-ZrSiO₄ with additives of MgO was fabricated.

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The glass-forming regions were determined in rare earth oxide containing systems: BaO-YO_1.5 SiO₂ and BaO-LaO_1.5-SiO₂. A larger glass-forming region was found in the YO_1.5-containing system. Properties and Raman spectra were studied in the four series of glasses: (35-x) BaO⋅xYO_1.5⋅65SiO₂, (35-x) BaO⋅xLaO_1.5⋅65SiO₂, 35BaO⋅xYO^1.5⋅(65-x)SiO₂ and 35BaO⋅xLaO_1.5⋅(65-x)SiO₂, to find out the relationship between properties and structure of these glasses. It was found that Y³⁺ and La³⁺ ions behave as network modifiers in the structure, strengthening the glass network; that is, the replacement of BaO by YO_1.5 or LaO_1.5 decreases the thermal expansion coefficient and increases the glass transition and softening temperatures, Vickers hardness and packing density of the glasses. It was also found that Y³⁺ has a larger effect on strengthening the network because of its larger ionic field strength. In 35BaO⋅xYO_1.5⋅(65-x)SiO₂ glasses, there was an anomaly in the properties-composition relation, which was explained by the change of the relative contents of different kinds of SiO₄ units.

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It is well known that ferroelectric (non-centrosymmetric) crystals are capable of revealing “bulk photovoltaic effect” i.e. production of greater-than-band-gap voltages under uniform illumination. While having piezoelectricity at the same time, the ferroelectrics are considered to cause the photostrictive effect as the superposition of these two phenomena. This paper describes the photovoltaic and photostrictive effects in the (Pb, La) (Zr, Ti)O₃ (PLZT) system. The composition PLZT (3/52/48) was found to reveal the largest product value of the photovoltaic voltage and piezoelectric coefficient. The photostriction and photovoltaic voltage are strongly dependent on the preparation method such as grain size and remanent polarization even with the same composition. Using PLZT ceramics, a photodriven relay has been fabricated and a primitive relay function controllable by the optical irradiation has been developed.

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Local structures around Ag⁺ ions in ion-conducting glasses in the system AgI-Ag₂O-GeO₂ were investigated by Ag K EXAFS (extended X-ray absorption fine structure) analysis. By using Ag₂O and AgI crystals as reference samples, average Ag-O and Ag-I distances for three kinds of glass samples were estimated from |F(r)| curves to be 2.15-2.22Å and 2.74-2.87Å, respectively. The Ag-O atomic distances suggest that a part of Ag⁺ ions locate near the polygermanate anions which consisted of GeO₄ tetrahedra. As the Ag⁺ ions of this type are strongly bonded to O^2- ions, they do not contribute to the ionic conduction. It was also concluded on the basis of the Ag-I atomic distances that the rest of Ag⁺ ions locate at tetrahedral sites surrounded by four I^- ions. Since the coodinations of these Ag⁺ ions are similar to those of Ag⁺ ions in AgI crystals which show ionic conductivity, the Ag⁺ ions of this type contribute to the ionic conduction.

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In order to prepare acicular particles of Al(NH₄)CO₃(OH)₂ (AACH), ammonium alum (AA) and NH₄HCO₃ (AHC) solutions were mixed at room temperature, and the precipitate was aged in the mother liquor at 60°-120°C in a closed vessel. Effects of ageing conditions on kind of products and their shape and size were investigated. AACH was formed with an excessive amount of AHC over the stoichiometry. Insufficient amounts of AHC produced boehmite. The AACH particles were single crystalline and acicular or lath-like, and long and short axes corresponded to crystallographic c and a axes, respectively. The length of particles was increased by the addition of acid solution such as H₂SO₄, HCl and HNO₃ to the mother liquor in which the precipitates were aged. The AACH particles seemed to be formed from the reaction of amorphous substances, which formed at room temperature, with the ageing solution during ageing at temperatures of 60°-120°C. Gamma-Al₂O₃ particles obtained by thermal decomposition of AACH particles at 1000°C possessed acicular shape of the parent crystals.

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The R-curve evaluation was discussed for “Fractometer”, and was applied to the short bar specimens of sintered silicon nitride. The values of K_R were increased slowly with crack extension. The K_R value of crack extension less than about 2mm could not be determined, because of the “pop in” phenomenon prior to the initiation of the stable fracture. When the increment of the applied displacement was stopped, the load relaxation due to subcritical crack growth was observed. Thus, it is concluded that the measured K_R values are likely to be the K_I values of subcritical crack growth corresponding to the crack opening displacement rate of the specimens.

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The objective of present investigation was to understand the relationships between the microstructure and electrical properties of semiconducting Sb doped SnO₂ glaze as a functional material. High electrical conduction is attributed to the three dimensional conduction network by highly conductive solution layers formed in the vicinity of undissolved semiconducting SnO₂ particle surfaces. Crystalline SnO₂ particles smaller than 8nm in diameter, responsible for high conductivity, were found in the solution layer with a high resolution TEM. A model experiment with the semiconducting SnO₂-glass diffusion couple showed that the conductivity changed non-linearly with distance from the surface of an undissolved semiconducting SnO₂ particle into the matrix region.

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