Ultrafine WC_1-x powder has been prepared as a single phase by a newly designed radio-frequency thermal plasma apparatus and its thermal stability and catalytic activity were examined. WO₃ was found to be appropriate as a starting material and the mole ratio of CH₄/WO₃ was also found to be better with over than 15 in order to obtain WC_1-x in the range of 90-95 wt%. Specific surface area of the WC_1-x powder was measured to be 34m²/g, of which particle diameter was calculated to be 10 nm. Particle diameter of WC_1-x was observed to be 5-20 nm by TEM and it was dispersed relatively well. It was stable thermally below 1, 000°C under Ar atmosphere but it began to decompose to W₂C over 1, 000°C and seemed to change to W at 1, 300°C. On the catalytic activity of WC_1-x it became clear that the ultrafine WC_1-xpowder promoted the formation of n-butane in the hydrogenation reaction of cis-2-butene.

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The effects of the additions of a small amount (4 mass%) of Al, Cr and Si on the densification behavior of Cu fine powder of 5 μm, which is usuable for metal injection molding (MIM), were investigated in relation to the relative density of green compact (Dg≅52 and 92%) and sintering atmosphere (H₂ and vacuum).
The results obtained were as follows: (1) In H₂ gas sintering, Cu-Al, -Cr and -Si compacts did not densified to full density in the same way as Cu compact for Dg≅52%. For Dg≅92%, however, Cu-Al and -Cr compacts completely densified. (2) In vacuum sintering, Cu-Al, -Cr and -Si compacts also did not completely densified for Dg≅52%, differing from Cu compact. For Dg≅92%, the results were nearly the same as those in H₂ sintering. The Cu-Si compact did not completely densified in any case, or even expanded. (3) These results could be explained mainly by the equlibrium gas pressure ratio of H₂O/H₂ in the reduction reaction of the oxide with H₂ gas, the sinterability of the oxides of added elements, adsorbed H₂O gas, etc.

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The mechanism of the synthesis of SiC powder by carbothermic reduction of silica has been studied. The rate of reduction of SiO₂ powder with coarse graphite particle was measured by means of thermogravimetry at temperatures from 1923 K to 2073 K under an argon atmosphere. Reduction products were investigated by chemical analysis and microscopic observation.
Reduction products are both SiC and SiO. The growth of SiC layer is observed at the surface of the graphite particle.
At the early stage of the reaction, the synthesis of SiC is controlled by the reaction of the gaseous compomnent, SiO with the graphite surface. The formation of the continuous layer of SiC around the graphite particles shifts the rate-determining step to the diffusion process of carbon through the SiC layer.

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Cutting tools of Ti(C, N)-Cr₃C₂ ceramics have better wear resistance than those of TiC-TiN cermet and WC-Co alloy tools for carbon steel. Ceramics of this system have the fracture toughness K_1c of 2.5 MPa⋅ m1/2. Higher fracture toughness is necessary for wider application. Therefore, addition of metal and B₄C to Ti(C, N)-Cr₃C₂ system was examined. The main results obtained are as follows:
(1) Adding each small amount of Ni and Co powder can improve not only density but also K_1c of Ti(C, N)-20 wt%Cr₃C₂ ceramics.
(2) Adding over 10 wt%Cr₃C₂ to Ti(C, N)-Cr₃C₂-(2-4) wt%Ni system makes big chromium carbide lamps or slender pools in the structure. Adding 5 wt%Cr₃C₂ to system, however, makes homogeneous materials.
(3) These HIPed homogeneous materials have the transverse rupture strength of 900-1100 MPa and K_1c of 3.5-4 MPa⋅m^1/2. It is considered that the improvement of K_1c was caused by Ni rich phase and the partial dissolution of Ni in the (Ti, Cr) (C, N) and chromium carbide phases.
(4) Ti(C, N)-Cr₃C₂-B₄C bodies containing over 10 wt%Cr₃C₂ and 1-2 wt%B₄C consist of (Ti, Cr) (C, N), CrB₂ and a small quantity of chromium carbide.
(5) The sintered bodies of Ti(C, N)-20 wt%Cr₃C₂-2 wt%B₄C-0.5 wt%Ni have the porosity of 0.1 vol%, the transverse rupture strength of 650 MPa and K_1c of 3.8 MPa⋅m^1/2. It is thought that the improvement of K_1c is caused by the (Ti, Cr, Ni) (C, N) which is round grains, and a little chromium carbide and CrB₂ which penetrate among the (Ti, Cr, Ni) (C, N) grains.

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Cr₃C₂ ceramics are expected to be applied to the furnace rail for slab reheating furnace in steel making industry, because of their better characteristics; high temperature stability, oxidation resistance and scale resistance. However, the effect of HIP conditions on the properties of Cr₃C₂ ceramics has not been clarified.
This report deals with the degree of sintering of chromium carbide system ceramics with C/Cr atomic ratio of 0.54 to 0.83 by HIP. The results obtained are as follows:
(1) The degree of sintering of chromium carbide is remarkably effected by carbon content. From the properties required, the content should be 13.4 wt%.
(2) Chromium carbide green compact forms the dense layer by a presintering in vacuum. This compact can be consolidated by HIP above a relative density of 89%, compared to that of 95% without presintering.
(3) Fracture toughness measured through D.T. method was 4.2 MPa⋅M1^1/2 and crack propargation velocity was 9×10^-3m/s.

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Addition of Mo₂C and TiN to TiC-Cr₃C₂ ceramic composite was tryed to develop for cutting tool materials. The compacts of the powder mixture consisting of 70%TiC-15%TiN-7%Mo₂C-8%Cr₃C₂ were sintered at temperatures up to 1600°C for 2 hr in a vaccum of 10^-1 mmHg having feeble carburizing attribute.
The compacts showed distinguished sintering ability similar to liquid phase sintering of alloys. That is to say, the compacts attained complete densification by sintering at 1350°C.
Mo₂C was dissolved in TiC readily at temperatures below 1200°C, which resulted in the formation of (Ti Mo) C solid solution. It was presumed that Mo₂C was dissolved in the form of ζ-MoC having NaCI type cubic lattice. It is likely that carbon content in the solid solution was substantially reduced due to the dissolution as MoC, because no metallic molybdenum was detected in the specimens in which Mo₂C was dissolved in TiC. It means the increment of carbon vacancy in the solid solution. This promotes dissolution of TiN into (Ti⋅Mo)C solid solution, which will play an important role as the main driving force of densification.
At 1350-1400°C, metallic impurities of iron group in the ceramic composite of about 0.8%, as well as that in TiC-Cr₃C₂ system, were fully dissolved into low-chromium carbides.

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The formation behaviour and magnetic properties of iron carbides (Fe₃C, Fe₅C₂) with acicular particles were investigated. The particles were prepared by the reaction of various starting acicular particles (α-Fe, α-Fe₂O₃, Fe₃O₄) with CO gas. The formation behaviour of the iron carbides was affected by the kinds of starting particles. α-Fe particles resulted in the formation of only Fe₃C at 450-500°C. On the other hand, α-Fe₂O₃ starting particles yielded Fe₅C₂ at 375-400°C or Fe₃C at 450-550°C. When the starting particles were Fe₃O₄ particles, Fe₅C₂ was formed at 375-400°C. The formed iron carbides particles lose the acicular form during the carburization. The magnetic properties of Fe₃C particles prepared from α-Fe at 500°C were as follows: σs: 90 emu/g, Hc: 600 Oe, σr/σs: 0.4.

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It was found that the binder phase frequently appeared around Vickers hardness indentation (V.H.I.) to form dotted structure of binder in TiC-based cermets at high temperature, and this phenomenon was never found in WC-based cemented carbides. Then the present study as to the phenomenon was carried out using TiC-(0, 20) vol%TiN-20 vol%Mo₂C-(5-20) vol%%Ni cermets in relation to the alloy composition, structure and hardness testing conditions. It was made clear that the appearance of the binder phase was influenced by the factors mentioned above, and also caused by the fact that the plastic flow of the binder phase under compressive stress due to V. H. I. occurred more easily than that of the alloy, depending on the alloy structures, testing temperatures, etc.

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The effects of the alumina content, alumina particle size, and flux of the alumina substrate and the W particle size of the W paste on the metallizing bonding strength and the relationship between the metallizing bonding strength and co-firing temperature were examined. The relationship between the W metallizing bonding strength and the co-firing temperature was changed largely as the alumina content, alumina particle size, flux, and W particle size changed. We obtained the metallizing bonding strength of 40 N/mm or higher even at the cofiring temperature of 1450°C by setting the alumina content to 93.1%, alumina particle size to 1.1μm, and W particle size of the W paste to 0.4μm. We assumed that this matallizing bonding strength was produced since the glassy phase generated when the alumina substrate was sintered was strongly engaged to the W network formed at a high temperature.

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In this investigation, the friction and sliding wear characteristics of new Mo₂FeB₂ complex boride base cermets against copper were studied, compared with a tool steel and cemented carbides. Two types of wear tests were carried out under lubricated and unlubricated conditions.
The main results obtained are as follows;
(1) Under a fluid lubricated condition, lapped surfaces of all materials do not show any significant frictional coefficient difference. In all tested sliding velocity from 0.06 to 1.2m/s, the frictional coefficient of all materials increases with increasing surface roughness. With increasing sliding velocity, the frictional coefficient of the tool steel drastically increases. On the other hand, that of the boride base cermet and the cemented carbide decreases after showing a maximum at 0.3m/s.
(2) Under a mild friction without lubrication, as same as the cemented carbide, the boride base cermet has a little higher frictional coefficient, but shows much lower wear volume than the tool steel.
(3) Under a severe friction without lubrication, the wear of the boride base cermets is less than that of the tool steel and the cemented carbide.
Concerning the wear resistance against pure copper under these conditions, the boride base cermet is superior to the cemented carbide.

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A mixture of aluminum alloy powder, 2024, and 2 wt% of nickel powder has been mechanically alloyed in a vibratory ball mill to investigate the effects of process variables on mechanical properties of the consolidated products. It was found that ball charge and powder charge played important roles on tensile properties; in as-work-ed specimens, milling with lower ball charge or lower powder charge was desirable to achieve good results. In T6-treated specimens, however, higher ball charge gave rather good tensile properties. Changes in ball size and mill pot capacity showed little effect on tensile properties. Process control agent was another variable which played an important role on mechanical properties. Carbon and graphite were effective additives for improvement of tensile strength; both ambient and elevated (200°C) tensile strengths increased with their addition. Though addition of zinc stearate also brought an increase in room temperature strength, it was bad to ductility.

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We made magnetization measurements on superconducting YBCO and BSCCO films with high c-axis orientation and found a universal dependence of normalized magnetization hysteresis ΔM/ΔM₀ on normalized magnetic field H/H₀ along the c-axis, where ΔM₀ is the magnitude of hysteresis ΔM at H=0 and He is the “irreversibility field.” This relation between ΔM/Δ M₀ and H/H₀ is excellently fitted by a single curve irrespective of temperatures and materials investigated. Except for H'-H₀, ΔM/Δ M₀ decreases exponetially with H/H₀, while in the vicinity of H₀ the data deviates from the exponential dependence. On the basis of the flux creep model, we succeeded in interpreting the universality by employing a logarithmic dependence of the effective pinning potential on current J at high density, which was recently proposed by Zeldov et al., and a linear J dependence at low density formerly proposed by Anderson and Kim.

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Recently, Tokura et al. suggested a structural classification method for copper oxide superconductors by the concept of "Block Layer". The method is very useful as guiding principle to design a new crystal structural high-Tc superconductor. We propose to classify "Block Layer" by the concept of "Layer". That enables us to predict new "Block Layers" and we can design many new superconductors.

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This paper reviewed the synthesis of copper oxide superconductors under high and high oxygen pressure. The oxygen doping under high oxygen pressure brings various interesting phenomena on the structure and propertis of superconductors. On the other hand, the CuO₂ layer is well stabilized under very high pressure. The high pressure technique is one of the useful route to synthesize new superconducting materials.

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The silver-sheath technique is most powerful for preparing the high Tc superconducting tapes. It comprises a serial step of handlings. A general feature of this process is firstly introduced. The recent developments of Y123, Y124, Bi2212, Bi2223 and T1 oxide tapes have been reviewed. Problems which should be solved for the present technique and a future scope are discussed. Fundamental investigations are emphasized to be still very important in this scientific field.

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Single-phase superconducting YBa₂Cu₄O_y has been synthesized at 780-790°C under one atmosphere oxygen pressure with the sol-gel powder precursor method. The precursor was derived from citrate metal-ion complexes dispersed in a solvent mixtures of ethylene glycol and water. From X-ray diffraction analysis, the material was found to be single phase. The superconducting transition observed in terms of complex susceptibility showed that the onset temperature of superconducting transition is 87.8 K and the transition width (10-90%) is 4.5 K.

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High pressure synthesis was performed on 123 and 124 phases in Y-Ba-Cu-O system under a pressure of 3GPa at 950°C. Lattice parameters and superconducting properties changed with an annealing duration under pressure in 123 phase with oxygen content X=7. The 123 product obtained from raw materials with X=8.5 had a tetragonal lattice with a=c/3=3.87A. Its real oxygen content could be estimated to be 7.3 from the lattice parameter, Raman spectroscopy, and also Rietveld analysis. The product seemed to be semiconductor containing a small amount of superconductor. 124 phase was obtained by a reaction at 950°C with its successive annealing at 700°C under 3GPa adjusting oxygen content of raw material to the exact composition of the product.

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In this report, we describe the phase diagrams for the pseudo-ternary system YO_1.5-CaO-CuO at 980°C and 1000°C in air. CaCu2O3 is formed at 1000°C but not at 980°C. Phase identification and structure analysis were done by means of powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). A new ternary solid solution formulated as Y45-xCxCussOy (24<X<33) was found. The XRD and electron diffraction (ED) patterns can be indexed by assuming that the solid solution has orthorhombic structure, typically with a=10.579 b=2.835, and c=6.231[Å] for x=30. The structure is modulated one-dimensionally along a direction between [110]* and [210]*, the wavelength and the direction varying with x. The change in lattice parameter with composition is anisotropic. And the unit cell volume decreases with increasing Y content. The melting point has been determined by means of TG-DTA.

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Structural and electrical properties of the system crystallizing in K₂NiF₄ structure, Nd₂-xSrxNiO₄ (O≤X≤1.4) were studied. Powder X-ray diffraction data were analyzed by the Rietveld method to determine the bond lengths. Tetragonality in the lattice parameters, c/a, shows a maximum at x=0.6, while, distotion of a NiO6 octahedoron, Ni-O(2)(//c-axis) /Ni-O(1)(//a-axis), monotonously decreases. No Jahn-Teller distotion appears in a Ni3+ region. From the measurements of Seebeck-coefficient and conductivity, the change in conduction mechanism was observed at x=0.6.

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We attempted synthesis of a single-phase Bi₂Sr₂Ca_1-xY_xCu₂O_y (0≤x≤0.4) from citrate sol-gel precursors and the dependence of the superconducting transition on the hole concentration was studied. The main advantages of the sol-gel precursor method are the shorter reaction time, the elimination of some steps such as centri-fugation and a fine control of pH. Powder X-ray diffraction analysis showed that the samples have a single phase, except for x = 0.1. The superconducting transition was measured in terms of complex susceptibility. The highest transition temperature T(onset) was observed for the x = 0.1 sample being 95.2 K. The results for five samples with different values of x are described.

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The formation behavior of an amorphous phase in grinding and its recrystallization behavior by heat-treatment of seed-added powder were observed using a starting powder of the high Tc phase (2223 phase) superconductor having the composition Bi_1.5Pb_0.4Sr_2.0Ca_2.0Cu_3.2O_y. The effects of uniaxial press-forming in the opposed anvil type high pressure apparatus were investigated in relation to the properties of sintered compacts (bulk density, phase microstructure, critical temperature, etc.).
Grinding the starting powder in agate mortar for 10-20 min initiated the formation of an amorphous phase and nearly completely amorphous phase was obtained by grinding for 100min. The heat treatment (at 850°C for 2h) of the amorphous powder which was added by 50 wt % starting powder as seeds, result-ed in the recrystallization to high Tc phase (2223 phase) in the presence of a trace of low Tc phase (2212 phase)
Starting powder packed in a copper ring gasket was press-formed under high pressure (0.5-1.5 G P a) . A small amount of low Tc phase coexisted with high Tc phase in the specimen formed at 1.0 G Pa. The bulk density of the sintered compact prepared by the subsequent sintering at 850°C for 40h under one atmospheric pressure was 5.4g/em, and the critical onset and offset temperatures were 115K and 103K, respectively.

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Superconducting properties of hot-pressed BiPbSrCaCuO (2223 phase) were studied. The bulk density was obtained to be -6.2 g/cm³ with pressure of 250 kg/cm² and independent from hot-pressing temperature. The critical current density Jc at 77K was measured by a four-probe method and the value of 2, 600 A/cm² was obtained. From the magnetization measurements ( by using VSM ), it was supposed that there is a certain correlation between transport properties and grain-growth process. The magnetic shielding effect was improved by using of hot-press method. Furthermore, it turned out that the shielding effect was more improvable by annealing after hot-pressing.

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A low-temperature growth technique for high Tc superconducting thin films has been developed using microwave plasma assisted reactive evaporation. Superconducting thin films of YBa₂Cu₃O_x with the critical temperature higher than 80 K have been successfully grown on SrTiO₃ and MgO substrates. Emission spectroscopic study of plasma revealed that a part of the metals as well as the oxygen were excited and that the reaction between the vaporized metals and the activated oxygen occurred at the surface of the substrates. Superconducting thin films were also prepared on the Si substrates without a buffer layer. However, their crystallinity, as well as their superconducting properties, were inferior to those of the films on the SrTiO₃ and MgO substrates. A TEM study revealed that two types of interfacial layer were formed between the film and the Si substrate: an amorphous silicon oxide layer and a Ba-excess diffusion layer. These amorphous layers are thought to interfere with crystallization of the film deposited on Si.

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Plasma-enhanced CVD is one of the promising methods for low-temperature growth of oxide superconducting films which is required for the electronic applications. This review reports recent studies on low-temperature growth of oxide superconducting films by plasma-enhanced CVD. Y-Ba-Cu-O films can be grown at a temperature as low as 515°C by microwave plasma-enhanced CVD using β-diketonate organometallic complexes as metal sources. Bi-Sr-Ca-Cu-O films can be grown at around 610°C by rf plasma-enhanced CVD using metal halide sources. Optical emission spectroscopy in the growth chamber reveals that the CVD reaction mechanism can be changed by exciting organometallic complexes.

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Superconductive thick film was prepared by a screen printing method on MgO and YSZ polycrystalline substrates. The paste was prepared by calcined powder of Bi₂Sr₂CaCu₂O_y.The textured orientation with c-axis of the superconductive phase was observed in the XRD patterns of partially melting and slow cooling samples. The Tc and lattice constant c of the film the annealing condition at low temperature in O₂ and N₂. It's suggested that the result was attributed to the oxygen nonstoichiometry in Bi₂Sr₂CaCu₂O_y.

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Bi₂Sr₂CaCu₂O_x ceramic powder prepared by a soled-state reaction was encapsulated in Ag pipe with a dimension of 6^φ(O.D.) ^-4φ(I.D.) x 200^lmm. The outer diameter of the pipe was decreased to 1^φmm by using a rotary swaging machine. The thin wires thus obtained were made up into a bundle, and the bundle was again processed by swaging to make a rod with multiple cores. A bullet was prepared by charging the rod into Cu can, and it was hot-extruded at relatively low degree of sectional area decrease. This procedure produced a highly efficient superconducting ceramic wire with multiple cores.

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A Bi(Pb)-Sr-Ca-Cu-O superconducting tube has been developed for a magnetic shielding. The tube, which was composed of supercoducting grains oriented to the axis of the tube, was made to roll the C-axis oriented green sheets prepared by a doctor blade method. As the magnetic field was applied parallel or vertical to the axis of the tube, the magnetic densities were shielded up to 34 gauss and 24gauss by the tube, respectively.

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Effects of a sintering plate (Ag and Al₂O₃) on the formation of superconductive phases in the superconductive Bi-Sr-Ca-Cu-O ceramics have been investigated. It is found that the specimen sintered on the Ag plate (860°C×60h) is doped with silver evaporated from the Ag plate, and the amounts of the silver and the high-Tc phase (110 K) in the specimen decrease with distance from the Ag plate. Increase of silver content in the specimen is quite efficient to enhance the formation of the high-Tc phase.

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Ultrafine Sr-Ca-Cu-O [Sr:Ca:Cu = 1:1:2] powders having diameter of less than 200 nm was prepared by a RF-plasma CVD technique and the ultrafine powders was mixed with powdered Bi₂O₃ at a composition of Bi:Sr:Ca:Cu = 4:3:3:6 to synthesize the superconductive Bi-Sr-Ca-Cu-O ceramics. Then the mixed powder was sintered at 820 - 880°C for 10 - 60 min.
When the mixed powder is sintered at 820 - 850°C for 10 min, the high-Tc phase (110K) is formed in the sintered specimen, but sintering longer than about 30 min caused a decrease in the high-Tc phase. In the case of sintering temperature at 860 - 880°C, only the low-Tc phase (80 K) is formed in the sintered specimen.

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Ca-free (Pb/Cu)-3212 phase in a Pb-Sr-Yb-Cu-O system has been studied. Almost-single phase samples were synthesized at a nominal composition of (Pb_2.1Cu)Sr₂(Yb_1-xSr_x)Cu₂O_y(0.0≤x≤0.3) by annealing in nitrogen. The sample at x=0.3 exhibited superconductivity with T_c(onset)=65K, T_c (zero resistivity)=17K. The powder X-ray diffraction pattern for x=0.3 sample could be indexed with orthorhombic symmetry of a=5.384Å, b=5.424Å and c=15.764Å. Thermogravimetric analysis and annealing treatments at various temperatures in nitrogen suggested that the crystallizing temperature for the (Pb/Cu)-3212 sample at x=0.3 was estimated to be 720°C.

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The effects of Ba-addition to the high-Tc phase in the Bi-Pb-Sr-Ca-Cu-O system have been studied for starting compositions of Bi:Pb:(Sr_1-x, Ba_x):Ca:Cu=0.96:0.24:1.0:1.0:1.6 with x=0 to 0.30 heated at 845 or 850°C. The characterization of the samples has been made by XRD, DTA, the measurements of DC electrical resistivity and AC susceptibility, SEM and WDX. The Ba-addition in the range of 0.005≤x≤0.10 promotes the formation of the high-Tc phase due to lowering of the partial melt. Tc increases to 112K for the sample with low Ba contents, while Ba-free sample exhibits Tc=106K. The tetragonal lattice constants are a=5.412 Å for all samples, but c=37.10 Å and 37.20 Å for x=0 and 0.2, respectively. WDX experiments clearly reveals that the high-Tc phase contains a small amount of Ba as a solid solution.

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Substitution effects of Pb in Bi₂Sr_3-y Ca_y CU₂O_z have been studied. The solubility of Pb depends upon the Ca/Sr ratio as well as the atmospheric oxygen pressure. Monophasic products can be obtained in a range of O<x<0.7 for Bi_2-xPb_xSr_1.5 Ca_1.5Cu₂O_z if these are treated in Ar at 700°C after being treated, as usual in air at 820°C. The structure symmetry changes from tetragonal to orthorhombic as Pb content increases. The modulation period is elongated monotonically as x increases, finally the modulation disappearing at x=1.2 for Bi_2-xPb_xSr_1.5Ca_1.5Cu₂O_z. The monophasic region is thus rather narrow, however the changes in lattice constants for the 30Å-phase appearing in a wide variety of multi phase samples suggest that monophasic region would be considerably widened if the stoichiometry of 2:3:2 is not observed.

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We studied the substitution of Ba to the Bi_2+xSr_2-xCu_1+x/4O_z solid solution system which was carried out by solid state reaction. From the phase diagram of the BiO_1.5-BaO-SrO-CuO system, it was obviously found that the substitution of Ba is only at the Sr site rather than the Bi site. The single phase solid solution region is 0.2<x<0.5, O<y<0.7 for the composition of Bi_2+x(Sr_2-x-yBay)Cu_1+x/4O_z. All the products sintered in air were semiconductive. The sintered specimen with a composition of Bi_2.2Sr_1.5Ba_0.3Cu_1.05O_z was further heat treated at 600°C in O₂. It also did not show superconductivity until 4.2K even though it behaves metallic.

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A single phase powder with the composition of Bi_1.8Pb_0.4Sr_2.0Ca_2.0Cu_3.2O_y was sintered with the small amount of Ag₂O or compositional oxides. The bulk density, microstructure and superconductive characteristics of the sintered specimens were examined to investigate the effect of the additive oxides on the sinterability and superconducting properties. The bulk density was of 4.3-4.6g/cm³ for the sintered specimens with 0.05-0.1mol addition. Their resistivity curves were divided into three groups, i.e. (a) without additive, Bi₂O₃ or PbO, (b) SrO, CaO or CuO and (c) Ag₂O. From SEM photographs it was observed that the sintered specimens were composed of the three main layer parts consisting of surface layer, orientated layer, and center layer part with disordered orientation. The thickness of the disordered layers in the center part decreased with decreasing the thickness of the specimens. The excellent result of Jc (77K) was shown by the sintered specimen with 0.1mol addition of SrO.

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The effect of Cadmium (Cd) substitution on the 2212 phase of the Bi-Sr-Ca-Cu-O superconducting system has been studied. The zero resistivity temperature, T_c (offset) initially increased with increasing Cadmium content. However, there exist an optimum amount of Cadmium doping that can be introduced into the system. Once this level is reached, further addition of Cadmium (Cd) causes a decrease in the transition temperature. This is due to the formation of the 2201 phase and other impurity phases. Electrical resistance measurements showed a maximum, T_c (offset), at 90.7K for the sample with nominal composition Bi_1.4 Cd_0.6 Sr_2.0 Ca_1.0 Cu_2.0O_y.

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Bi₂Sr₂CaCu₂O_x ceramic powder prepared by a solid-state reaction was encapsulated in Cu can with a dimension of 33_φ(O.D.) - 20_φ(I.D.) ?? 65lmm. The bullet (can containing ceramic powder) was preheated at 840°C for about 10 min, and was extruded rapidly to prepare a long specimen with the length of about 500 mm. An outline design of the containner for the hot-extrusion, and some experimental results were reported in this note.

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The Bi-Pb-Sr-Ca-Cu-O thin films with different composition were prepared on MgO single crystal (100) by rf magnetron sputtering using multi targets:Bi_0.5Pb_{0. ??} O_z, CaCu_0.75O_z, SrCu_0.75O_x. The obtained films were two-step-annealed to crystallize. The crystalline phase of the annealed films were greatly depended on the 2nd annealing temperature. Low temperature(about 820°C) annealing films were composed of C-axis orintated low-Tc phase (Bi(Pb)₂Sr₂Ca₁Cu₂O_x). The high-Tc phase(Bi(Pb)₂Sr₂Ca₂Cu2O_x) produced by higher temperature annealing and the films annealed at about 840°C contained both of C-axis orientated low-Tc phase and high-Tc phase. Moreover high temperature (about 850°C) annealing films were composed of C-axis orientated high-Tc phase. From the SEM photograhs of the films annealed at low temperature and at high temperature region. the plate-like crystals of low-Tc and high-Tc phase stacked on each other with C-axis orientation (orientation structure). However, the films annealed in temperature region between them were composed of the mixture of the plate-like crystals with C-axis orientation and with almost perpendicular to the substrate (mixed structure). The sensitivity in magnetic field showed low for the films with orientation structure. On the other hand, it showed high for the films with mixed structure. It implied that the weak-link well produced at grain boudary in the mixed structure.

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The effects of uniaxial-press on the formation of the high-Tc phase in the Bi-Pb-Sr-Ca-Cu-O system studied through X-ray diffraction experiments, density measurements, SEM and DTA. Samples with a starting composition of Bi:Pb:Sr:Ca:Cu=0.96:0.24:1.0:1.1:1.6 was heated at 850°C for various period (1st-sintering), pressed uniaxially at 0.5 to 2.0 GPa, and heated at 850°C for 72h (2nd-sintering). Density increases as pressure increases and 1st-sintering period extends. Volume fraction of the high-Tc phase after 2nd-sintering reaches high values but is independent of pressure for samples subjected to 1st-sintering. Orientation ratio after 2nd-sintering, which is estimated from peak intensity ratio, decreases for 1st-sintering periods ?? 24h as pressure increases, while it increases and reaches high values for the period of 48h. The uniaxial-press is effective in high-denstisifacation, high-orientation and promotion of the formation of the high-Tc phase for samples heated at 850°C for 48h before press.

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Rapidly solidified Bi-Sr-Ca-Cu-O (2:2:2:3) glassy ceramics was produced by gas atomization. Spherical powder less than 20μm was obtained more than 50%, and 1/3 of product was coiposed of thin fibers, which had one or two heads of round particles or had several knots. Both of powder and fiber were amorphous, the crystallization temperature was about 500°C. The 3.0nm phase appeared above 800°C, and formed plate like crystals gathering to be aggregates equivalent to primary particles. Liquid phase broke out above 860°C, and 2.4nm phase remained without forming 3.7nm phase.

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