Investigation of composition variations near grain boundaries in high-quality sintered samples of YBa2Cu3O7−δ

Babcock, S. E.; Kelly, Tom; Lee, Peter J.; Seuntjens, J. M.; LaVanier, Lori A.; Larbalestier, D. C.

doi:10.1016/0921-4534(88)90070-6

Cited by 62 publications

(13 citation statements)

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“…The increase of misorientation across the boundaries leads to an effective larger grain-boundary area, which in turn behaves as a resistive-type grain boundary and, hence, lower transport J c . This is in good agreement with the earlier reports [14][15][16][17][18] where the J c of the basal plane grain boundaries is found to be decreasing with increasing misorientation across the boundary. That is, when the tilt angles of the grain boundaries are more than 20°, they behave as a weak link.…”

Section: ͓S0003-6951͑97͒03022-2͔supporting

confidence: 93%

“…[1][2][3][4][5][6][7][8][9][10][11][12] Although the intragranular critical current densities, J c approach the intrinsic values, the intergranular weak links still limit the current carrying capacity. 2,5,[13][14][15][16][17][18] Microstructure and granularity problems are the key issues of great interest. Here, we report high-resolution Auger electron spectroscopic ͑HRAES͒ results, and address the nature and thickness of the grain boundaries in laser ablated YBa 2 Cu 3 O 7Ϫ␦ thin films.…”

Section: ͓S0003-6951͑97͒03022-2͔mentioning

confidence: 99%

“…The initial fall or rise in the concentrations are often taken to reflect grain surface compositions. 13,14,23,24 They, however, attain a steady state after short sputtering. The residual concentrations after long sputtering (ϳ12-14 min) are the composition at the interface of the film and the substrate.…”

Section: ͓S0003-6951͑97͒03022-2͔mentioning

confidence: 99%

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Enhanced Jc and improved grain-boundary properties in Ag-doped YBa2Cu3O7−δ films

Selvam

Seibt²,

Kumar

et al. 1997

Applied Physics Letters

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A large increase (∼8×) in critical current density, Jc, was achieved for in situ laser ablated YBa2Cu3O7−δ–Ag films. High-resolution Auger electron spectroscopic investigation indicates that the Ag-doped films are stoichiometric with a relatively low grain-boundary extension (8 nm) in contrast to undoped YBa2Cu3O7−δ films (32 nm). Further analysis suggests that the doped film contains a much lower silver content (<0.15 wt %) than in the target material (5 wt %). These observations are in excellent agreement with the temperature dependence of Jc, the room-temperature resistivity, and the surface resistance results. Thus, Jc enhancement in Ag-doped films can be attributed to their superior properties, viz., improved microstructure characteristics and the reduced resistive grain boundaries.

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Section: ͓S0003-6951͑97͒03022-2͔supporting

confidence: 93%

Section: ͓S0003-6951͑97͒03022-2͔mentioning

confidence: 99%

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Enhanced Jc and improved grain-boundary properties in Ag-doped YBa2Cu3O7−δ films

Selvam

Seibt²,

Kumar

et al. 1997

Applied Physics Letters

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“…These sites serve as either nonsuperconducting or weakly superconducting regions, which have the effect of lowering the T c . 23 This nonstoichiometry effect is documented 24 in the high-T c copper oxide La 2Ϫx Sr x CuO 4Ϫ␦ , 25 where fluctua-tions in T c have been shown to be compositionally dependent upon x. It is then plausible to suggest that the T c estimated through magnetic-susceptibility measurements is a measure of bulk intragrain superconductivity in our materials, while the resistivity measurements are more dependent on intergrain superconductivity.…”

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confidence: 80%

Superconductivity in germanium clathrateBa8Ga16Ge30
Bryan¹,
Srdanov²,
Stucky³
et al. 1999
Phys. Rev. B
58
2
17
0
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“…Roth et al 13 concluded that for copper-rich compositions close to the stoichiometric composition, partial melting occurs for temperatures in the range of 950-1,000°C, so local inhomogeneity could lead to partial melting in some areas. Babcock et al 10 did observe grain boundary wetting by a copper-rich phase at about 20-25% of grain boundaries in materials sintered at 975°C. However, their results for boundaries free of second phase also suggest copper enrichment and oxygen depletion.…”

Section: Grain Boundary Chemistry and Electron Transportmentioning

confidence: 99%

Grain Boundaries and Jc in High-Tc Oxide Superconductors

Kroeger

1989

JOM

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In metallic superconductors, grain boundaries are effective pinners of magnetic flux and, as such, are partially responsible for high critical current densities achievable in those materials. However, in the highcritical-temperature oxide superconductors, grain boundaries have been identified as the source of problems leading to the low critical current densities exhibited by bulksintered material. The very short superconducting coherence lengths of the oxides make their electrical and magnetic properties exceedingly sensitive to microstructural inhomogeneities, thus placing stringent requirements on the quality of grain boundaries. Recent studies of grain boundary chemistry and its effects on critical current density have shed some light on the problem.10 Jlm Figure 1. A scanning electron micrograph of a fracture surface of YBa2Cup7~ fractured in the Auger system. The platelet grain mOrphology is evident. Transgranular and intergranular areas can be identified on the basis of morphology. For example, the analysis areas marked 1 and 2 are grain boundary surfaces.If you want more Information on this subject, please circle reader service card number 52. LL INTRODUCTIONFrom the beginning, the excitement generated by the discovery of superconductivity at temperatures higher than 77K has been tempered by the realization that, for bulk applications, improvement in one important materials parameter has been obtained at the expense of another. The long-studied, low-transitiontemperature metallic superconductors such as NbTi and Nb Sn readily support high current densities (l05-106 Ncm 2 ) in high magnetic fields (lOT or more), while the new oxide superconductors, with transition temperatures in the range of92 to 124K, typically have critical current densities three to five orders of magnitude lower when prepared in bulk polycrystalline forms. Development of high critical current density (high-J c ) material prepared by powder processing routes would be a major step toward utilizing high-critical-temperature (high-Tc) oxide superconductors in energy-related applications such as power generation, motors, energy storage and transmission.Early success! in obtaining high current density in thin films ofYBa2Ct1a07~ grown epitaxially on SrTiO a single crystal substrates indicated that critical currents are not intrinsically low in that material, and focused attention on grain boundaries and the anisotropy of J c (with respect to both the crystal lattice and an applied magnetic field) as probable causes ofthe poor current densities obtained in sintered material. The highly anisotropic crystal structures of all of the presently known high-Tc oxides lead to strongly anisotropic electron transport properties in both the normal and superconducting states. For example, in or-

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Investigation of composition variations near grain boundaries in high-quality sintered samples of YBa2Cu3O7−δ

Cited by 62 publications

References 13 publications

Enhanced Jc and improved grain-boundary properties in Ag-doped YBa2Cu3O7−δ films

Enhanced Jc and improved grain-boundary properties in Ag-doped YBa2Cu3O7−δ films

Superconductivity in germanium clathrateBa8Ga16Ge30
Bryan¹,
Srdanov²,
Stucky³
et al. 1999
Phys. Rev. B
58
2
17
0
View full text Add to dashboard Cite

Grain Boundaries and Jc in High-Tc Oxide Superconductors

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Investigation of composition variations near grain boundaries in high-quality sintered samples of YBa2Cu3O7−δ

Cited by 62 publications

References 13 publications

Enhanced Jc and improved grain-boundary properties in Ag-doped YBa2Cu3O7−δ films

Enhanced Jc and improved grain-boundary properties in Ag-doped YBa2Cu3O7−δ films

Superconductivity in germanium clathrateBa8Ga16Ge30Bryan1, Srdanov2, Stucky3 et al. 1999Phys. Rev. B582170View full textAdd to dashboardCite

Grain Boundaries and Jc in High-Tc Oxide Superconductors

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Superconductivity in germanium clathrateBa8Ga16Ge30
Bryan¹,
Srdanov²,
Stucky³
et al. 1999
Phys. Rev. B
58
2
17
0
View full text Add to dashboard Cite