Applied Superconductivity最新文献

{"title":"Effect of Ag doping on structure andcritical temperature of Bi2Sr2CaCu2O8+δ superconductors","authors":"T.A. Deis ,&nbsp;M. Lelovic ,&nbsp;N.G. Eror ,&nbsp;U. Balachandran","doi":"10.1016/S0964-1807(98)00045-3","DOIUrl":"10.1016/S0964-1807(98)00045-3","url":null,"abstract":"<div><p>The effects of Ag substitution for Bi, Sr and Cu on the <em>c</em><span>-axis lattice parameter and critical temperature (</span><em>T</em>_c) were determined for the Bi_{2−<em>x</em>}Sr_{2−<em>y</em>}CaCu_{2−<em>z</em>}O_{8+<em>δ</em>} (BSCCO-2212) superconducting phase. Two distinct regimes of behavior were observed: fast cooling represented the regime where the uptake of excess oxygen was the controlling factor and slow cooling represented the regime where the cation content was the controlling factor on the structure and properties. Samples showed higher <em>T</em>_c values and longer <em>c</em>-axes with increased cooling rate. A linear increase in <em>T</em>_c with increase in <em>c</em>-axis length was observed for the faster-cooled samples. For the slow-cooled samples, increased <em>c</em>-axis length was observed when Ag was substituted for Bi and Sr, whereas substituting Ag for Cu caused no change in <em>c</em>-axis length. In addition, any deviation from the ideal 2212 stoichiometry was shown to reduce the <em>T</em>_c<span> values of samples that were slowly cooled and fully oxygenated. Preliminary results obtained by high-resolution transmission electron microscopy coupled with electron energy loss spectroscopy indicated that relatively small amounts of Ag (≈1 at.%) can occupy Bi sites and a larger amount (≈10 at.%) of Ag can substitute for Cu.</span></p></div>","PeriodicalId":100110,"journal":{"name":"Applied Superconductivity","volume":"6 6","pages":"Pages 279-284"},"PeriodicalIF":0.0,"publicationDate":"1998-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0964-1807(98)00045-3","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81308502","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bi(2223) thick films (TC(0)=109K) on Ba2GdNbO6: a new perovskite ceramic substrate for BSCCO superconductor","authors":"J. Kurian,&nbsp;K.V.O. Nair,&nbsp;P.K. Sajith,&nbsp;Asha M. John,&nbsp;J. Koshy","doi":"10.1016/S0964-1807(98)00068-4","DOIUrl":"10.1016/S0964-1807(98)00068-4","url":null,"abstract":"<div><p>Ba₂GdNbO₆<span> has been developed as a new substrate suitable for the BSCCO superconductor. Ba</span>₂GdNbO₆<span> has a complex cubic perovskite (A</span>₂BB′O₆<span>) structure with a lattice constant </span><em>a</em>=8.587 Å. The DTA studies revealed that there is no phase transition occurring in Ba₂GdNbO₆<span> in the temperature range of 30–1300°C. The thermal expansion coefficient of Ba</span>₂GdNbO₆ is found to be 7.913×10⁻⁶°C⁻¹. The dielectric constant and loss factor of Ba₂GdNbO₆ are in a range suitable for its use as a substrate for microwave applications. The Bi(2223) superconductor does not show any detectable chemical reaction with Ba₂GdNbO₆<span> even under extreme processing conditions. The thick films<span> of Bi(2223) dip-coated on polycrystalline Ba</span></span>₂GdNbO₆ substrate gave a <em>T</em>_C(0) of 109<!--> <!-->K and a current density of approximately 4×10³ A/cm² at 77<!--> <!-->K and zero magnetic field.</p></div>","PeriodicalId":100110,"journal":{"name":"Applied Superconductivity","volume":"6 6","pages":"Pages 259-265"},"PeriodicalIF":0.0,"publicationDate":"1998-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0964-1807(98)00068-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84394006","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bidirectional transmission of single flux quanta","authors":"D. Zinoviev","doi":"10.1016/S0964-1807(97)00026-4","DOIUrl":"https://doi.org/10.1016/S0964-1807(97)00026-4","url":null,"abstract":"","PeriodicalId":100110,"journal":{"name":"Applied Superconductivity","volume":"25 1","pages":"599-602"},"PeriodicalIF":0.0,"publicationDate":"1998-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78686891","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stress analysis in melt processed RBa2Cu3O7 (R=Y, Nd) by micro-Raman spectroscopy","authors":"R Provoost ,&nbsp;K Rosseel ,&nbsp;D Dierickx ,&nbsp;R.E Silverans ,&nbsp;V.V Moshchalkov ,&nbsp;H Kojo ,&nbsp;M Murakami","doi":"10.1016/S0964-1807(98)00100-8","DOIUrl":"https://doi.org/10.1016/S0964-1807(98)00100-8","url":null,"abstract":"<div><p>We have performed a detailed analysis of the micro-Raman spectra recorded around the non-superconducting <em>R</em>₂BaCuO₅ inclusions embedded in different melt grown <em>R</em>Ba₂Cu₃O₇ (<em>R</em><span>=Y, Nd) samples. The Raman spectra were recorded every 0.4 or 0.5</span> <em>μ</em>m along a line crossing one or more inclusions on two specific samples. Sample A, YBa₂Cu₃O₇ with 33<!--> <!-->vol% of Y₂BaCuO₅<span> was prepared following a fast-melt-processing scheme. The cooling rate of the melt, crossing the peritectic temperature, was 180°C/h. We observed a downshift of the phonon modes of the superconducting phase around the inclusions. This softening can be related to the presence of tensile stresses around the inclusions. Sample B, NdBa</span>₂Cu₃O₇ with 40% of Nd₄Ba₂Cu₂O₁₀<span> was prepared following an oxygen-controlled-melt-growth method. A cooling rate of 1°C/h was applied to produce this sample. In this case we found a hardening of the phonon modes of the superconducting phase around the inclusions towards the energy of the phonon modes obtained in single crystals. Again, this shift of the Raman peak position can be related to the variation of mechanical stress around the inclusions. The hardening can be caused by the relaxation of tensile stress in the superconducting matrix around the inclusions.</span></p></div>","PeriodicalId":100110,"journal":{"name":"Applied Superconductivity","volume":"6 2","pages":"Pages 185-192"},"PeriodicalIF":0.0,"publicationDate":"1998-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0964-1807(98)00100-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91636907","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Anisotropy of E(I) characteristics of Ag-sheathed BSCCO tapes with respect to external magnetic field","authors":"P Ušák,&nbsp;L Janšák,&nbsp;F Chovanec","doi":"10.1016/S0964-1807(97)00045-8","DOIUrl":"https://doi.org/10.1016/S0964-1807(97)00045-8","url":null,"abstract":"<div><p><span>Because of the macroscopic form of Ag-sheathed BSCCO-2223 tape conductors, as well as internal structure of grain build up and their mutual orientation within the Ag sheath, their volt–ampere characteristics are not isotropic with respect to external magnetic field orientation. For the same absolute field values the behaviour of </span><em>E</em>(<em>I</em><span>) curves are a sensitive gauge of vector B inclination to tape axis and to the surface plane. As a result of the proximity effect and the weak links structure, the increasing external magnetic field reduces overall integral current capacity of the sample. The effect is pronounced at a perpendicular orientation of B but an analogic picture is observed for planar orientation with a corresponding shift of </span><em>E</em>(<em>I</em>) curves to higher current levels. For selected and gradually increasing levels of external magnetic field the difference in the vector B, parallel and perpendicular inclination with respect to tape plane on <em>E</em>(<em>I</em>), characteristics are presented. In this way the anisotropy manifestation at the different field levels is studied. The field vector remains perpendicular to tape axis. Also revealed is the influence of thermal cycling on <em>E</em>(<em>I</em>) through the thermomechanically induced cracking process.</p></div>","PeriodicalId":100110,"journal":{"name":"Applied Superconductivity","volume":"4 12","pages":"Pages 577-581"},"PeriodicalIF":0.0,"publicationDate":"1998-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0964-1807(97)00045-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91760105","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magnetic measurements in NdBa2Cu3O7−δ single crystals: magnetization, flux pinning and creep","authors":"M.R. Koblischka ,&nbsp;T. Higuchi ,&nbsp;S.I. Yoo ,&nbsp;M. Murakami ,&nbsp;T. Frello ,&nbsp;M. Baziljevich ,&nbsp;T.H. Johansen ,&nbsp;T. Wolf ,&nbsp;P. Diko","doi":"10.1016/S0964-1807(98)00105-7","DOIUrl":"10.1016/S0964-1807(98)00105-7","url":null,"abstract":"<div><p>In this paper, we present the results of various magnetic measurements on an NdBa₂Cu₃O_{7−<em>δ</em>} (NdBCO) single crystal. Special features observed in the magnetization loops (MHLs) are discussed. From these loops, critical current densities, <em>j</em>_c as a function of the applied field, <em>H</em>_a, and volume pinning forces, <em>F</em>_p=<em>j</em>_c×<em>B</em>, are derived. The samples exhibit a strong fishtail or peak effect at temperatures above 30<!--> <!-->K. In a small temperature window between 50<!--> <!-->K and 74<!--> <!-->K, even three peaks are seen in the <em>j</em>_c(<em>T</em>,<em>H</em>_a) curves. A good scaling of the <em>j</em>_c (<em>T</em>,<em>H</em>_a) curves is obtained, which allows the identification of the peaks. The scaled volume pinning forces (vs the reduced field, <em>h=H</em>_a/<em>H</em>_irr), in the temperature regime between 60 and 90<!--> <!-->K give experimental evidence for a strong pinning at extended superconducting defects (interaction volume <em>V</em>_pin∼<em>ξ</em>²<em>d</em><span>). These defects are ascribed to spatial composition fluctuations found in light rare earth superconductors, providing a scatter of the transition temperature, </span><em>T</em>_c. Furthermore, the scaling analysis of <em>F</em>_p is extended towards low temperatures. It is shown that at 5<!--> <!-->K another peak in <em>F</em>_p is found, which is due to pinning at twin boundaries. Using this scaling analysis of both <em>j</em>_c and <em>F</em>_p<span>, the irreversibility line (IL) is determined in the entire temperature range 0–92</span> <!-->K. Magneto-optic (MO) imaging is employed to investigate the flux distributions of various NdBCO single crystals. These images confirm the important role of twin boundaries as pinning sites at low temperatures and low applied fields.</p><p>PACS numbers: 74.60 Ec, 74.60 Ge, 74.60 Jg</p></div>","PeriodicalId":100110,"journal":{"name":"Applied Superconductivity","volume":"6 2","pages":"Pages 225-234"},"PeriodicalIF":0.0,"publicationDate":"1998-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0964-1807(98)00105-7","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91420625","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Pulsed-field magnetization applied to high-Tc superconductors","authors":"U. Mizutani ,&nbsp;T. Oka ,&nbsp;Y. Itoh ,&nbsp;Y. Yanagi ,&nbsp;M. Yoshikawa ,&nbsp;H. Ikuta","doi":"10.1016/S0964-1807(98)00106-9","DOIUrl":"10.1016/S0964-1807(98)00106-9","url":null,"abstract":"<div><p>The pulsed-field magnetization (PFM) technique has been elaborated as the most efficient and effective tool in magnetizing the melt-processed high-<em>T</em>_c<span> bulk superconductor in the temperature range 30–80</span> <span><span>K. The dynamic motion of magnetic fluxes penetrating into the YBCO superconductor during the PFM operation has been analyzed and the flux </span>propagation speed<span><span> has been accurately evaluated. The viscous force is found to play a very crucial role in the </span>PFM process. Detailed analysis of the flux motion in the presence of both viscous and pinning forces enabled us to find a very efficient method for magnetization by the PFM operation. The iteratively magnetizing pulsed field operation with reducing amplitudes abbreviated as ‘IMRA’ has been developed and proved to be very effective in magnetizing high-</span></span><em>T</em>_c superconductors at temperatures as low as 30<!--> <!-->K. By making full use of these findings, we constructed a prototype quasi-permanent magnet system capable of producing magnetic field of 0.8<!--> <!-->T in the outerspace at 7<!--> <!-->mm above the surface of the magnetized YBCO superconductor.</p></div>","PeriodicalId":100110,"journal":{"name":"Applied Superconductivity","volume":"6 2","pages":"Pages 235-246"},"PeriodicalIF":0.0,"publicationDate":"1998-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0964-1807(98)00106-9","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85252150","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Key issues for the characterization of RE–Ba–Cu–O systems (RE: Nd, Sm, Eu, Gd)","authors":"M Murakami","doi":"10.1016/S0964-1807(98)00087-8","DOIUrl":"10.1016/S0964-1807(98)00087-8","url":null,"abstract":"","PeriodicalId":100110,"journal":{"name":"Applied Superconductivity","volume":"6 2","pages":"Pages 51-59"},"PeriodicalIF":0.0,"publicationDate":"1998-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0964-1807(98)00087-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90965075","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"OCMG process for filamentary Nd123 superconductor produced by solution spinning","authors":"Tomoko Goto,&nbsp;Masahide Takahama,&nbsp;Takuji Kimura","doi":"10.1016/S0964-1807(98)00096-9","DOIUrl":"10.1016/S0964-1807(98)00096-9","url":null,"abstract":"<div><p><span>The oxygen controlled melt growth (OCMG) process for filamentary Nd123 superconductors has been studied to enhance the </span><em>J</em>_c values. The filamentary Nd_1.18Ba_2.12Cu_3.09O_<em>x</em> (1) and Nd_1.25Ba_2.05Cu_3.10O_<em>x</em> (2) precursors were prepared by dry spinning through a homogeneous aqueous solution containing mixed acetates of Nd, Ba and Cu, poly(vinyl alcohol). The calcined filaments were partially melted in flowing 0.1% O₂+Ar. The <em>T</em>_c values of filament (1) was 94.5<!--> <!-->K and 88.5<!--> <!-->K for filament (2). By controlling the heating condition, maximum <em>J</em>_c values of 2.4×10⁴ A/cm² and 1.8×10⁴ A/cm² at 77<!--> <!-->K and 0<!--> <!-->T were attained for filaments (1) and (2), respectively. A window of the optimum heating conditions for filament (2) was narrow and the reproducibility of the high <em>J</em>_c value was poor.</p></div>","PeriodicalId":100110,"journal":{"name":"Applied Superconductivity","volume":"6 2","pages":"Pages 157-162"},"PeriodicalIF":0.0,"publicationDate":"1998-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0964-1807(98)00096-9","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90202083","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of Nd4Ba2Cu2O10 addition on the pinning properties of Nd-Ba-Cu-O crystals","authors":"T. Mochida,&nbsp;N. Chikumoto,&nbsp;M. Murakami","doi":"10.1016/S0964-1807(98)00104-5","DOIUrl":"https://doi.org/10.1016/S0964-1807(98)00104-5","url":null,"abstract":"<div><p>We have studied the effects of Nd₄Ba₂Cu₂O₁₀ (Nd422) on the pinning characteristics of NdBa₂Cu₃O_{7−<em>δ</em>} (Nd123) crystals. Like Y₂BaCuO₅ particles in the Y–Ba–Cu–O system, the addition of Nd422 could enhance critical current density <em>J</em>_c at lower fields. The peak field (<em>B</em>_pk) and the <em>J</em>_c value at <em>B</em>_pk were almost independent of Nd422 contents although a slight decrease in <em>J</em>_c at <em>B</em>_pk was observed with increasing Nd422 contents. The normalized relaxation rate (<em>S</em>) increased for all the samples when the field exceeded <em>B</em>_pk. The addition of Nd422 was effective in preventing a rapid increase in <em>S</em> above <em>B</em>_pk. The exponent <em>μ</em>, defined in the collective creep model, was deduced by fitting the experimental data and was found to show strong field dependence. We found that <em>μ</em> changes from positive to negative at around <em>B</em>_pk<span>, suggesting that the flux creep mechanism is different below and above </span><em>B</em>_pk.</p></div>","PeriodicalId":100110,"journal":{"name":"Applied Superconductivity","volume":"6 2","pages":"Pages 217-224"},"PeriodicalIF":0.0,"publicationDate":"1998-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0964-1807(98)00104-5","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91636906","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}