The single crystal of YBa₂(Cu_1-xFe_x)₃O_y has been grown from a mixed region of solid Y₂BaCuO₅ and melt. The Ostwald ripening mechanism plays an important role for growth of large single crystal. The oxygen concentration of single crystal is controlled by oxygen-or nitrogen-annealing under various conditions. The single crystal of YBa₂(Cu_0.97Fe_0.03)₃O_y annealed in flowing O₂ gas shows a sharp superconductive transition at about 90K. The iron concentration included in the single crystal of YBa₂(Cu_1-xFe_x)₃O_y, which is determined by EPMA, increases with an increase of x, but is less than the nominal content x.

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We studied the ac-magnetic response of Co-doped YBa₂Cu₃O_7-d oxide superconductors, YBa₂Cu_3-xCo_xO_7-d (x=0.03-0.3), in terms of complex susceptibility X=X'-iX". The samples were synthesized by the modified polymerized complex method. For all the samples, the superconducting transition was observed. As expected, the onset temperature decreased with increasing x. We found that the magnetic shielding due to the weak-link coupling is completed within the temperature region smaller than that for the samples prepared by the original polymerized complex method. This indicates that the modified method presented here is more useful for fabrication of sintered ceramic superconductors with better homogeneity, i.e., with larger critical current density.

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We report Ca-site selectivity in the crystal structure of Y124(YBa₂Cu₄O₈) superconductor. We sucsessfully synthesized superconducting samples with nominal compositions of (Y_1-xCa_x)Ba₂Cu₄O₈ (series-A: x=0.0, 0.05, 0.1) and Y(Ba_2-yCa_y)Cu₄O₈ (series-B: y=0.0, 0.05, 0.1) by polymerized complex method followed by 0₂-IIIP technique. Neutron powder diffraction measurement has shown excess impurities in pmpotion to Ca-content in series-B. An extension of Δ T_c(10-90%) was also observed in series-B by AC-magnetic susceptibility measurement. It is suggested that the formation of these impurities in series-B originate from a discrepancy in ideal composion, that is, (Y_1-xCa_x)Ba₂Cu₄0₈ (seires-A). We conclude that Ca-atom preferentially substitutes Y-atom in the 124 structure for these reasons.

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Superconductivity of 1 unit cell thick (1-UCT) YBa₂Cu₃0₇ (YBCO) with various oxide cap layers is studied. Capping with BaO layer makes 1-UCT YBCO superconducting. It is revealed that that a formation of BaO-CuO-BaO charge reservoir is of significance for the hole donation in the 1-UCT YBCO. Superconductivity or significant reduction of resistivity implying the formation of the charge reservoir was also observed in 1-UCT YBCO covered with Sr-O, Ca-O, Pb-0, and Cd-O.

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Y-Ba-Cu-O (YBCO) superconducting films were prepared on SrTiO₃(100) substrates by metalorganic chemical vapor deposition. The precursors used were β-diketone chelates of Y, Ba and Cu. The YBCO films, having superconducting transition temperature defined by zero resistivity (T_c(R=0)) above 90 K and critical current density (J_c) over 10⁶ A/cm² at 77 K and O T, were obtained at the conditions of oxygen partial pressure (Po₂) and deposition temperature (T_dep) near the CuO-Cu₂O-O₂ equilibrium line (Po₂=3.6 Torr-T_dep=850°C and Po2=0.036 Torr-T_dep=700-720°C). The films prepared at these conditions showed J_c over 10⁴ A/cm² at 77 K in high magnetic fields above 20 T. The nano-composite structure of the YBCO films was studied by transmission electron microscopy. CuO and Y₂Cu₂O₅ grains with a size of 0.1-2 μm were included. The precipitates of about 10 nm in size were observed in the matrix of the YBCO films.

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Since the discovery of superconductivity in the La-Ba-Cu-O system, various compounds with high T_c have been investigated in a short time. However, phase diagrams have not been well-established except for the Y-Ba-Cu-O system. In particular, we can not obtained monophasic Pb-free "2223" phase in the Bi-Sr-Ca-Cu-O system at the present stage. In general, phase diagram study provides a basic knowledge on exploring of new compounds and elucidation of reaction processes. Thus, the phase diagram study for the Bi-Sr-Ca-Cu-O system is significant and indispensable to reveal the reaction process for the Pb-free "2223" phase. Phase diagrams for YO_1.5-SrO-BaO-CuO system, BiO_1.5-SrO-CaO-CuO system and LaO_1.5-BaO-CuO system were reviewed based on our experimental results.

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The composition around Bi₂CuO₄ in the Bi₂O₃-CuO system was studied using DTA and X-ray analysis. Only the compound Bi₂CuO₄ was confirmed in the Bi₂O₃-CuO system as reported previously. The eutectic temperature was observed between 750°C to 760°C, which is 10°C to 20°C lower than the value previously reported. The monoclinic (α-form) to cubic (δ-form) transition of Bi₂O₃ was observed at 730°C, which is in good agreement with the previous studies.
The interesting crystallization of γ-Bi₂O₃ was observed in the narrow composition range about 60-50 mol % Bi₂O₃ when it was quenched above 760°C in air. However, α-Bi₂O₃ was observed in the more Bi₂O₃ rich composition at 70 mol % B1₂0₃.

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Thermal behavior of the Bi-2223 phase in the Bi, Pb-Sr-Ca-Cu-O system, especially segregation and dissolution reaction of the "3321" phase which was identified as Sr_2.5Bi_0.5Pb₃Ca₂CuO₂, has been studied by XRD, SQUID and resistivity measurements. On annealing below 830°C in air, the "3321" phase precipitated from the 2223 crystals. When the 2223 phase was annealed at 750°C in O₂stream, the precipitation of the "3321 " phase increased. On annealing at 750°C in Ar stream, however, no precipitation of the "3321" phase was detected. By reheateing at 850°C even for 1min, the "3321" phase was almost dissolved into the mother 2223 crystals. When the 2223 phase was reheated at 750°C in Ar stream after annealing at 750°C in air, the "3321 " phase disappeared. On the contrary, the "3321" phase was stable on reheating at 870°C in O₂ stream. Therefore, it seems that the "3321" and the 2223 phase coexist in epuilibrium in a high oxygen partial pressure.

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Thermal behavior of the Pb-substituted Bi-2201 with various compositions was examined by XRD and SEM. Bulk samples were annealed in the temperature range from 600°C to 800°C and subsequently reheated at 750°C to 830°C in air. Various Pb-compounds precipitate by annealing in the temperature range from 600°C to 800°C and dissolution of the precipitates by subsequent reheating in the temperature range from 750°C to 830°C. The kind of the Pb-compounds and the temperature range in which these reactions occur depend upon the composition of the "2201" phase. The precipitation and dissolution of the Pb-compounds were confirmed with morphological observations with a SEM of a fixed portion of a sample before and after heat treatments. Remarkable grain-growth of the "2201" phase was observed in Bi_1.7Pb_0.8Sr_1.5CuO_z reheated at 750°C, indicating the formation of liquid.

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Mechanical grinding and reforming process of the Pb-substituted 2223 phase has been studied for the monophasic samples with a composition of Bi_0.9Pb_0.2SrCaCu_1.6O_Z. The 2223 phase changes to ultla-fine powder by full grinding, exhibiting no magnetic response, while the ultra-fine powder and the small 2223 crystals coexist in samples ground for short periods. Some second phases were formed in the ground powder subjected to heating at temperatures between 500°C and 800°C. On the other hand, annealing of the bulk samples below 800°C leads to precipitation of the 3321 phase identified as Sr_2.5Bi_0.5Pb₃Ca₂CuO_Z. Precipitation of second phases in the coexistent powder was interpreted by those in ultra-fine powder and bulk samples.

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The Pb-substitution effects on crystal structure and Tc were examined in samples of Bi-2212 phase with a composition of Bi_4-xPb_xSr₃Ca₃Cu₄O_z(O≤x≤2.2). The crystalline symmetry of the Pbsubstituted 2212 phase depends upon Pb-composition: tetragonal(x≤0.4), orthorhombic(A)(0.6≤x≤1.4) and (B)(1.6≤x≤2.0). It is noteworthy that a considerable portion of Pb maybe located at the Sr site besides the Bi site in orthorhombic(B) while Pb occupies the Bi site in orthorhombic(A). Thermal behavior of Pb-substituted 2212 phase was also studied by characterizing samples annealed at 400°C in air and subsequently reheated at 800°C in Ar. Interesting precipitation and dissolution on reactions were found.

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The change of the Bi-2223 phase Bi_1.8Pb_0.4Sr_2.0Ca_2.0Cu_3.2O_z with repeat of mechanical grinding and heating at 850°C in air has been studied mainly by XRD. The repeat of the process leads to the decrease of the 2223 phase and formation of the 2212 phase, (Ca, Sr)₂CuO₃ and (Sr, Ca)₃Cu₅O_x. This change depends upon two experimental factors : the accumulative heating period and the number, N, of repeat. The former bring more significant effects than the latter. The Pb concentration in the samples was found to decrease as N increased. The change of the 2223 phase mentioned above can be interpreted by the decrease in the Pb concentration in the samples.

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Wires in which Bi₂Sr₂Ca₁Cu₂O₈ (Bi-2212) and Ag layers were alternately coated on Ag tape were prepared by the dipping method. In order to increase the Jc value of wires, conditions of heating processes I and II were investigated. When heating I was made in the condition where holding temperature inducing a partial melting of the Bi-2212 phase was 887°C and cooling rate was 5°C /h and heating II was carried out at 850°C, the Jc value was improved intensively. It has been found that laminating Ag on the Bi-2212 layer and reducing the oxygen partial pressure of flowing gas are effective to increace the Jc value. A wire with a maximum Jc value of 1.8xl0⁴A/cm² (at4.2 K in 1T) was prepared, and overall critical current (Ic) was increased to more than 300A. which was measured by double stacking the Bi-2212 and Ag layers at 4.2K in magnetic field of 1T.

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We report the result of laser irradiation on surface of the bulk of oxide superconductor Bi system (2223-phase) prepared by solid state reaction method. The irradiation is accompanied by oxygen gas blow. As the result of the laser ir-radiation to surface, we observed an increase of High-Tc phase intensity by the X-ray diffraction and the growth of the crystal on the surface on the SEM images.

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Bi-Pb-Sr-Ca-Cu-O superconducting films were prepared by Sol-Gel method using a solution of acetate and propionic acid. Starting solution with moler ratio of Bi_2.2Pb_0.4Sr₂Ca_2.2Cu_3.2O_y was spin-coated onto poly-crystal MgO, single-crystal MgO and Ag substrate and then heated to decompose after drying in air. Films were prepared by repeating the process from the coating to the decomposition for 10 times and these were sintered at 840-855°C for 30min. Bulk samples were also prepared for comparison. In the case of bulk samples, percent of 2223 phase increased from 49% to 63% when the sintering temperature rised from 840°C to 855°C. On the other hand, in the case of film samples of sintered at 855°C, the percent of 2223 phase was 10% on poly-crystal MgO but 85% on single-crystal MgO. Film sample sintered at 840°C on Ag substrate was composed of single phase of 2212 phase.

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We Prepared Bi-Pb-Sr-Ca-Cu-0 films on polycrystal MgO substrate by using sol-gel method. We soaked them in water, acetone, propionic acid, or solution of pH 2.0-4.7, and we investigated by X-ray diffraction and SEM methods how crystal phases and morphology changed by soaking.
For the sol-gel method, we chose metal acetates as solutes and propionic acid as a solvent without controlling pH. Although any change was not found on film samples soaked by water or acetone, the dissolution of Bi-system was found for the samples soaked by proplonic acid. The dissolution is considered as the reason why the thickness could not increase after several coating of starting solution without controlling pH. By controlling pH by addition of aqueous ammonia, we obtained the viscosity of starting solution of 42mPa⋅s and the thickness of coat-ing film.

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The superconducting properties of (Tl₁-_xPb_x)Sr₂Ca_{2 ??} Cu_3.2 O_Y were investigated. At the composition x = 0.5, evaporation of TI and formation of nonsuperconducting phase (Pb-rich compounds) were minimum. These sintered samples with composition of x = 0.5 were single-phased almost and had high critical temperature of 115K. By hot-pressing these composition, increase of 10 - 20 % and about 150 % were observed in density and in critical current density, respectively.

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The oxygen doping was tried under high oxygen pressure for various layered perovskite cuprates whose structures are described as ordered perovskite having distinct copperoxygen and nonmagnetic metal-oxygen layers. The oxygen doped samples showed lower resistivity than undoped ones but, in general, semiconductive. Some samples, for example, such as La_1-xSr_1+xGaCuO_5+z, have enough oxidation state of copper of 2.15-2.25 for the onset of superconductivity, but showed no superconductivity. The Cu-O distances obtained by Rietveld analysis were larger than that of hole doped copper superconduc-tors, which may spoil the effective hole dope in CuO₂ layer.

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Solubility of Cu to BaPbO₃ was investigated by firing mixtures of BaO₂, PbO₂ and CuO at 890°C for 42hours. BaPb_1-xCu_xO₃ type solid solution seemed to be formed in a compositional range of x<0.5. Two types of crystal structure were found out for the composition of Ba₂Pb CuO _?? . The phase 1 had a hexagonal lattice with a=6.085Å, c=15.02Å, and phase 2 had a tetragonal lattice with a=4.293Å, c=17.25Å. They can be related to the cubic lattice parameter a'of BaPbO₃ in relations of a??2_1/2a', c??2×3_1/2a' in the former, and a??a', c??4a' in the latter. These superlattices are due to the layer-by-layer orderings of copper oxide and lead oxide layers. The phase 1 changed to the phase 2 by firing 890°C in air flow for 20 hours and also even by keeping in ambient atmosphere for 4 days. The phase 1 was a semiconductor down to 4.2K with an electrical resistivity of 4.9×10Ωcm at room temperature.

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Effects of impurity contents in starting materials of YBa₂Cu₃O_x (123) ceramics on the critical transition temperature, T_c, and the critical current density, J_c, were investigated. Specimens for measurements of T_c, and J_c were fabricated by sintering and melt-growth techniques using reagents of various purity grades. Superconducting properties were affected with the purity of starting materials as well as the preparation techniques. As for sintered specimens, T_c, and J_c values increased 87.4-89.6K and 140-317A/cm² (at 77K, OT), respectively, with a decrease in impurity contents in starting materials. In the melt-growns pecimens, both T_c and J_c values were improved to be 90.0-92.9K and 235-960A/cm², respectively. In these specimens, with lowering impurity contents, T. values increased whereas J_c values decreased. All the sintered specimens showed similar microstructures with randomly oriented plate-like 123 grains, irrespective of impurity contents. On the other hand, fine grained needle-like 123 crystals and spherulitic microstructures were observed, in the melt-grown specimens, in which the 123 grains became smaller with an increase in impurity contents.

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To examine the effect of rhenium oxide addition on the superconducting properties of YBCO ceramics, Y₁Ba₂Cu₃Re_xO_y (YBCO) specimens with x=0 to 0.1 were prepared by both conventional sintering and melt-growth methods. It has been found that the addition of ReO₃ has significant effects on the critical temperature and critical current density of YBCO superconductors. By addition of Re_0.01, the critical temperatures of the sintered and meltgrown specimens were increased to 89.5K and 91.9K, respectively. The maximum critical current densities of the sintered and melt-grown specimens were 396A/cm² (Re_0.01), and 753A/cm² (Re_0.005), respectively. XMA and XRD analyses showed that some Re ion was incorporated in the YBCO crystal.

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There are thought to be two mechanisms by which the diamond is retained in the cutting wheel. The first is a physical factor based upon the young's modulus of the matrix, while the second is a chemical factor due to a reaction between the matrix and the diamond surface. However, it is not clear how is relationship between the retainability and cutting ability of the diamond.
In this study, the chemical factor was assumed to be constant by virtue of keeping the sintering temperature constant. Samples which had different mechanical properties were observed using a SEM and an EPMA, and were investigated by means of a bending test, and an actual cutting test.
As a result, it has been shown that the mechanical holding force of the matrix changed with the young's modulus, and the ratio of diamond pull-out, after the cutting test, is related to this physical factor.

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Formation of faults in ZnO grain by addition of some metal oxides were studied. Two kinds of faults were observed in non-ohmic polycrystalline ZnO (ZnO varistor): one is twin-type and the other is stacking-type. ZnO grains having twin structures were obsereved with specimens prepared by adding small amount of Sb₂O₃ (75ppm), Sc₂O₃ (75ppm) and SnO₂ (25ppm). The stacking structure in ZnO seemed change with the amount of additions. The formation mechanism of twinned structure obtained by addition of SnO₂ was unknown to date.

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We studied sintering behaviour of Mo powder compacts with an addition of P alloy powders. The relative densities of Mo powder compacts remarkably rose when sintered at 1300°C with an addition of 1.0wt% Fe-P powder and sintered at 1200°C with an addition of 0.5wt% Ni-P powder. This sintering promotion was due to the existence of the liquid phase. This liquid phase was produced at lower temperature than that where the Mo powder compacts were sintered with an addition of Fe and Ni powders. The decomposition of the added P alloy powders in the Mo powder compacts occurred at the temperature where the liquid phase was produced.

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By the reversion from hcp martensite (α') to bcc phase (β), refining of the microstructure with (α+β) two-phase was attempted in sintered Ti-(2-4)mass%Cr alloys. The relation between mechanical properties and micro-structures was also investigated for the specimens subjected to several heat treatments.
Quenching from β single phase region gives α' structure in the Ti-Cr alloys containing 2-4mass%Cr, and the annealing of α' in the (α+β) two-phase region leads to the formation of very fine micro-duplex structure of (α+β). The balance between tensile strength and elongation can easily be controlled by varying annealing temperature. In order to obtain excellent mechanical properties, however, β phase in the micro-duplex structure should be stable enough thermally and also against deformation.

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Effect of pores on the nitriding behavior of 12mass%Cr ferritic steel (SUS410L) compacts in nitrogen gas atmosphere was investigated by means of optical microscopy, chemical analysis and measurement of porosity. Porosity of compacts was controlled by varying presintering time at 1473K and repressing pressure of presintered compacts. Mechanical property of nitrided compacts was also estimated by three-point bending test. The results obtained are as follows:
(1)In the nitriding at 1473K, compacts with the open-porosity of more than 5vol.% can easily absorb 0.26mass% of nitrogen all over the specimen through open pores. When the open-porosity has been reduced to less than 5vol.% by presintering and repressing, however, compacts are nitrided only from the surface, so that the general nitriding rate becomes smaller.
(2)Owing to the absorption of 0.26mass% nitrogen, ferrite phase changes to austenite and the austenite transforms to martensite on cooling to room temperature.
(3)Repressing of sintered compacts is very effective for the densification, and this results in the increase in bending strength of sintered compacts with fully martensitic structure.

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Modification of a porous silicagel with the microporous carbon was studied for the purposes of controlling hydrophilic properties of the pore surface of silicagel and creating a novel porous material of dual uniform-pore structure. Silicagels of the mono-dispersed pore were impregnated in phenol resin dissolved into acetone, dried and heat-treated at 800°C for 1 hour to carbonize the resin onto the silica pore. The procedure was repeated up to seven times for the phenolic porous carbon to deposit cumulatively over the mesopore of the silicagel support. The adsorption capacities of steam, carbontetrachroride, TIPB (1, 3, 5-Triisopropylbenzene) and PFTBA (Perfluoro-tributylamine) were measured at 30°C. Effects of the microporous carbon deposit on the hydrophilic properties and molecular sieving properties were discussed.

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