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Volume 42, Issue 7
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[in Japanese]1995 Volume 42 Issue 7 Pages 776
Published: July 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (70K) -
Tomoichiro Okamoto, Ben Huybrechts, Masasuke Takata1995 Volume 42 Issue 7 Pages 777-780
Published: July 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSWhen a dc voltage above 5 V was applied to wire-like GdBa2Cu3O7-δ samples, a glowing hot spot appeared and moved to the negative electrode. The direction of movement could be reversed time after time by switching the polarity of the applied voltage. The samples were annealed by letting this glowing hot spot travel back and forth in the sample. The velocity of the hot spot depended on the direction of movement, however, for one direction the velocity of the hot spot decreased with annealing. After the hot spot moved back and forth 5 times, as well the density as the critical current density increased.View full abstractDownload PDF (2644K) -
Takahito Terashima, Eiji Komai, Yoshichika Bando, Toshio Kawahara, Tak ...1995 Volume 42 Issue 7 Pages 781-785
Published: July 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSWe have studied electric field effects on resistance and superconducting transition temperature of YBa2Cu3O7-δ (YBCO) using a heterostructure of Ag/BaTiO3(200nm)/SrTiO3(1.5nm)/YBCO (n-unit cells: n=10, 6, 2)/SrTiO3(substrate). The application of a negative gate voltage, Vgate' to the Ag electrode lowered the resistance of YBCO, while a positive Vgate having the opposite effect. The relative change in the normal state resistance ΔR/R, where ΔR is the field-induced change of resistance and R is the resistance at Vgate=0V, was well explained by the field-induced change of carrier density. ΔR/R at Vgate=1V remained constant above T0 at which the gradient dR/dT takes a maximum value. The field effect on the mean field transition temperature was found to be weaker than that on resistance.View full abstractDownload PDF (281K) -
Hiromasa Mazaki, Hiroshi Yasuoka, Masato Kakihana, Minoru Osada, Masah ...1995 Volume 42 Issue 7 Pages 786-791
Published: July 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSWe studied the magnetic response of Pr-doped Y2Ba4Cu7O15-d oxide superconductors, Y2-xPrxBa4Cu7O15-d (x=0.0-1.2) in terms of complex susceptibility x=x'-ix". The samples were synthesized by the polymerized complex method. For all the samples, the superconducting transition was observed. As expected, the onset temperature decreased with increasing x. By means of X-ray analysis, we determined the lattice constants, of which the Prcontent dependence showed a slight increase with increasing x. However, the variation is much smaller than those for the case of the 123 and 124 phase, suggesting that the charge state of Pr in the 247 phase can take either +3 or +4 state.View full abstractDownload PDF (309K) -
Hirotaka Fujimori, Masato Kakihana, Masatomo Yashima, Hiromasa Mazaki, ...1995 Volume 42 Issue 7 Pages 792-797
Published: July 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA systematic Micro-Raman spectroscopic investigation has been performed on YBa2Cu3-xCoxO6+y ceramic samples of different Co content x in the interval 0≤x≤1 which are prepared by a polymerized complex method. With increasing Co content an evolution of the defect induced Raman scattering of the CuO chain modes (550-650 cm-1 region) has been observed. The intensity of the defect modes has increased with increasing Co concentration, which has in turn suggested increased disordering of oxygen in the based (Cu/Co)-Oy plane. It has been infered from Raman spectroscopic results that the CuO chain disorder is closely related to Tc and a certain minimal size of the oxygen disordered (or ordered) domain is needed for a decrease in Tc (or the appearance of superconductivity).View full abstractDownload PDF (406K) -
Kazunari Yamaura, Zenji Hiroi, Mikio Takano, Syuji Hahakura, Jun-ichi ...1995 Volume 42 Issue 7 Pages 798-803
Published: July 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSBa-free mercury-based cupric oxide superconductors "(Hg, M)Sr2Can-1CunOy" (M=Re, Cr, Mo; n=2, 3) were prepared by using high-pressure technique. The substitution of M for Hg was found to be essential to the stabilization of the Ba-free phases, which are isostructural to HgBa2Can-1CunOy As-grown Re-doped sample was over-doped, and Tc varied systematically as a function of temperature of annealing in an evacuated quartz ampoule. The maximum TT thus attained is 120 K for Re-doped n=3 phase. As-grown Cr-doped n=3 phase was under-doped superconductor, and Tc up to 110K by oxidization. As opposed to samples of HgBa2Can-1CunOy' these compounds "(Hg, M)Sr2Can-1CunOy" (M=Re, Cr, Mo; n=2, 3) are stable in air at room temperature.View full abstractDownload PDF (1859K) -
Yasuo Takeda, Yasuo Mukai, Nobuyuki Imanishi, Osamu Yamamoto, Yasunori ...1995 Volume 42 Issue 7 Pages 804-807
Published: July 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe electrochemical oxidation was tried for La2-xBaxCuO4+2 system, especially in the well-known anomalous composition, x=1/8 where the superconductivity disappears. The samples were oxidized to La2-xBaxCuO4.05 whose superconductivity was perfectly recovered. The low temperature x-ray diffraction study showed that the successive phase transition (THT→OMT→TLT) seen in asprepared samples was perfectly suppressed by the oxygen dope.View full abstractDownload PDF (218K) -
Nobuyoshi Takabatake, Takashi Tsubota, Toshiaki Ishikawa, Tatsuhiro Ta ...1995 Volume 42 Issue 7 Pages 808-812
Published: July 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSBi-Pb-Sr-Ca-Cu-O superconducting films were prepared on single MgO substrate by sol-gel method . As the starting solution, we used acetates-solutes butyric acid with the addition of aqueous ammonia . The films were prepared by repeating the process of coating and decomposition (at 700 C for 30 min) 3 or 5 times and by finally sintering at 855°C. for 12h . In the composition of BiaPbbSr2.0Ca2.2Cu3.2Oy (M=a+b, b=0.3a), M was changed 2.6, 2.8, 3.0, 3.2 and 3.4 and it was found that the optimum composition was M=3.2, and when the high-Tc phase amounted to 67% and Tc0 (the critical temperature of zero resistance) = 93 K . As a reason of the existence of optimum M value, there was evaporation of Bi and Pb components which brought about impurities such as (Sr, Ca)2CuO3 for small M(≤2.8) . On the other hand for large M (≥3.0), it gave rise to precipitation of impurities such as CuO. We used Atomic Force Microscope (AFM) in observing surface microstracture, and we could find the height difference without sputtering gold in SEM observation.View full abstractDownload PDF (3617K) -
Takashi Tsubota, Toshiaki Ishikawa, Kentaro Ohhashi, Nobuyoshi Takabat ...1995 Volume 42 Issue 7 Pages 813-816
Published: July 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSWe prepared BiSrCaCuO superconducting film by spincoating-pyrolysis method using a solution of propionic acid dissolving Bi1.8Pb0.4Sr2Ca2Cu3.2Oy, oxide powder. As a result, film samples were mainly composed of the 2212phase. In order to increase the amount of the 2223phase, Ca and Cu acetates were added into the preceding solution and Bi:Sr:Ca:C??2:2:4:5 solution was prepared. On the film sample using the 2245 solution, the amount of the 2223phase increased by about 5 times. However impurity phases formed due to addition of Ca and Cu acetates bring about the increase of electric resistivty. X-ray diffraction lines of the 2223phase were broad and it shows that the 2223phase grew little because of the insufficiency of Pb-content.View full abstractDownload PDF (2576K) -
Preparation of Bi-Pb-Sr-Ca-Cu-O High Tc Thick Films on Ag or MgO Substrate with Superconductor PasteToshiaki Ishikawa, Takashi Tsubota, Kentaro Ohhashi, Nobuyoshi Takabat ...1995 Volume 42 Issue 7 Pages 817-820
Published: July 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSSuperconducting thick films (200± 50 μ m) were prepared by coating method on Ag or polycrystalline MgO substrate. The paste for coating was a mixture of single 2223 phase powder, an organic binder (PSO or polyethylenegrycol) and organic solvents, and it was prepared by calcined powder of Bi1.8 Pb0.4Sr2Ca2Cu3. 2Oy . In the film from the PSO binder and Ag substrate high Tc and high Jc were obtained for 20h sintering time.View full abstractDownload PDF (1463K) -
Katsuyoshi Hotta, Hajime Miyazawa, Yoshimitsu Ogawa, Masao Murakawa, H ...1995 Volume 42 Issue 7 Pages 821-824
Published: July 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA study on connecting of supercondoctors through laser treatment was conducted. Two kinds of Bi systems i.e., 2223 phase(sintered bulk) and 2212 phase(thin film prepared on MgO substrate) were used as the substances to be connected. Powders of the system which were pasted with two kinds of solvents, 2-butoxyethyl acetate and mixture of ethyl cellulose and terpineol, were used as the medium materials. Two pieces of respective specimen filled with the medium between them were installed on a jig system and settled on an X-Y table to be exposed to laser beam irradiation. A 160-350 W output CO2 laser beam accompanied by oxygen gas blow was irradiated, along the contact line of the substance, onto the medium at a speed 10 mm/min. Before laser treatment, the electric resistance of all specimen revealed almost constant value of about 600 Ω at temperature range concerned. After laser treatment, for the specimen which used the medium powder pasted with mixture of ethyl cellulose and terpineol, Tc(end) of 67.6 K and 47.0 K was obtained for 2223 phase and 2212 phase respectively, which leads to the connection of superconductors.View full abstractDownload PDF (1329K) -
Jinsuke Takata, Nobuyasu Kawai1995 Volume 42 Issue 7 Pages 827-832
Published: July 15, 1995
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe dimensional change behavior of the system Fe-2wt%Cu-0.8wt%C-0.75wt% zinc stearate was investigated under an atmosphere of dissociated ammonia and the results were compared with those of endothermic gas. The sintering process was divided into three stages ; delubricating, heating and cooling, and the sintering conditions were varied in each stage.
The decrease in the heating or cooling rate and the increase of dew point in an atmosphere caused shrinkage at all the stages. These behaviors in dissociated ammonia were very simple and in numerous cases differed from those in endothermic gas. The shrinkage was mainly caused by the decarburization, which began soon after reaching maximum temperature. "The modified carbon transfer theory " can be also considered to be appliciable to other sintering atmospheres. This theory is that the carburization during temperature rise contributes to the shrinkage but after reaching maximum temperature it contributes to the expansion and that the decarburizing have an opposite action of the carburizing.View full abstractDownload PDF (406K) -
Hisashi Kaga, Yoshihiro Taya, Katsumasa Yabe, Hisashi Kuwano, Ken-ichi ...1995 Volume 42 Issue 7 Pages 833-838
Published: July 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSUsing the vacuum mechanofusion apparatus which has been reported in this journal, the formation of Mo composite with Al2O3 core particles was conducted. The effects of the surrounding pressure on both of the processing behavior and the characteristics of the composite particles were discussed from the data of the specific surface area, particle size distibution and from the results of SEM observation, XPS and AES analyses.
The formation of composite particles progressed with processing time. As surrouding pressure decreased, the yield of formation was found to increase and the Mo coated surface became smoother. XPS analysis for Mo coated layer revealed that the thickness of oxide layer became thicker. While, AES elucidated that 0 content and its enriched depth in Mo coated layer formed under high vacuum was lower and shallower respectively than those formed in the air atmosphere.View full abstractDownload PDF (1791K) -
Hajime Iwasaki, Takuya Ohtani, Takasuke Mori, Mamoru Mabuchi, Kenji Hi ...1995 Volume 42 Issue 7 Pages 839-842
Published: July 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSCavitation of superplastic metal matrix (6061Al alloy) composite reinforced by 20% volume fraction of Si3N4, particulate and Si3N4, whisker has been investigated. A constant stress tention test was carried out at temperature of 818K and stress of 8MPa for the composite containing Si3N4, particulate, and at 833K, 10MPa for the composite containing Si3N4, whisker. Volume of cavity in the Si3N4p/6061Al composite was larger than that in the Si3N4w/6061Al composite at a range of strain up to 1.5. Both composites already included the volume of cavity of 0.6-0.8% at a strain of 0.2. Cavity volume fraction exponentially increased with increasing strain. Most cavities of both composites were nucleated at the interface of matrix and reinforcements. Cavities in the Si3N4p/6061Al composite were almost granular and those in the Si3N4w/6061Al composite were either granular or flat.View full abstractDownload PDF (4066K) -
Hajime Iwasaki, Yoshikazu Miyashita, Takasuke Mori, Mamoru Mabuchi, Ke ...1995 Volume 42 Issue 7 Pages 843-846
Published: July 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe Si3N4 particulate reinforced 6061Al(Al-Mg-Si) matrix composite, which included 20% or 30% volume fraction of reinforcement, denoted as the 20%Vf and the 30%Vf respectively, has been produced by powder metallurgical processing followed by hot extrusion at 773K with a reduction ratio of 100. The composites exhibited a typical superplastic behavior at a temperature of 848K for the 20%Vf and 823K for the 30%Vf, and a maximum elongation of 380% was obtained for the 20%Vf at a constant stress of 5MPa and 734% was obtained for the 30%Vf at a stress of 8MPa respectively. It has been clarified that these composites exhibited cavitation after a superplastic deformation. Cavity volume fractions exponentially increased with increasing strain in both composites. The cavity volume fraction of the 20%Vf specimen was less than that of the 30%Vf specimen at a strain up to 1.2. The maximum cavity volume fraction throughout the experiments was 2% at a strain of 1.5 for the 30%Vf specimen. SEM obsevation showed that cavities had always formed at interface between matrix and reinforcements, and the size of most cavities was less than 1μm. However, a few large cavities of more than 1μm in a mean diameter also appeared in both specimens in an early stage of straining. The larger cavities were grown rapidly and elongated parallel to the tensile axis with increasing strain which may cause the fracture.View full abstractDownload PDF (4263K) -
Sunao Sugihara, Mitsuhiro Iizuka, Yukie Kato1995 Volume 42 Issue 7 Pages 847-853
Published: July 15, 1995
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSThe effect of powder particle sizes of n and p-Bi2Te3 on the thermoelectric properties has been studied. The powder was formed from the each ingot and sieved into <63, 63-90 and 90-150μm for p-type, and <355 and >355 μm for n-type. Those powders are pressed followed by CIP, then sinterd at 773K for 7200s. The effects of CIP on the densities were not so large such as 1-4% depending on the powder sizes. The Seebeck coefficients and electric conductivities for p-type were 110μ V/K and 0.8x102Ω-1m-1 at 333K, while 180μ V/K and 2.0x104Ω-1m-1 for n-type, respectively. The thermal conductivity for n-type was 0.7W/mK leading to the figure of merit of 2.1x10-3(/K). The hybrid texture of the suitable amount of smaller and larger grains has a possibility of an improvement for thermoelectric properties.View full abstractDownload PDF (1795K)
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