Microstructural study of Y1Ba2Cu3O7-x/Ag samples irradiated with 60Co γ rays at high doses (original) (raw)
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In situstudies of microstructural changes in YBa2Cu3O7−xduring O and He irradiation
Philosophical Magazine A, 1989
We have studied the microstructural changes occurring in YBa,Cu,O,-, (the so-called '123' phase) upon room temperature irradiation by He+ and O', in situ, on samples that had been thinned by ion milling before irradiation, using a transmission electron microscope on line with the ion implanter. In previous work on samples crushed from the bulk or on films ion-milled after irradiation, the samples amorphized above a threshold of about 0 3 displacement per atom. In the present case, no amorphization is observed, instead, precipitation of Cu,O occurs, indicating complete demixing of the ceramic. This process seems to nucleate at the ion-milled surfaces. For a displacement-per-atom ratio of about 010, a change from the orthorhombic to the tetragonal structure of the '123' compound occurs. It is suggested that the result is quite general. The effects of the microstructural changes on the electrical properties are briefly discussed.
Effect of silver in Y1Ba2Cu3O7?x samples
Journal of Materials Science, 1994
Two techniques for preparing Y-Ba-Cu-O/Ag specimens are presented: (a) solid-state reaction, and (b) normal precursors dissolved in hot concentrated nitric acid and dried in air. The samples are characterized by scanning electron microscopy (SEM), scanning Auger, X-ray diffraction, optical microscopy and electrical resistivity measurements. In comparison with a normal 1-2-3 superconductor it was found that the normalized resistance [R(T)/R(280 K)] decreases for both preparation methods. The material retained a high initial temperature of superconductivity, Tc, for a maximum of 6% w/o Ag20 during solid-state reaction and 6.5% w/o Ag20 for samples dissolved in hot concentrated nitric acid and dried in air.
Irradiation of YBa2Cu3O7−δ single crystals by 5.6 GeV xenon ions
Physica C: Superconductivity, 1991
Single crystals of YBaZCu@_d were irradiated at 95 K by 5.6 GeV Xe ions and the evolutions of the superconducting resistive curves-measured parallel and perpendicular to the c axis-were determined in situ as a function of ion fluences. We find that pc and pob increase linearly with the fluence and even tend to saturate for the highest fluences. This behaviour strongly differs from that found for sintered samples irradiated under the same conditions for which a quasi-exponential increase of resistance was observed. Nevertheless our results confirm that energy deposition by electronic excitation plays a role in defect creation as previously reported in Xe irradiated sintered samples.
Physica C: Superconductivity, 1991
Electron microscopy has been carded out on the same thin regions of YBa2Cu307 before and after neutron irradiation. It was found that crushed as well as ion milled specimens did deteriorate strongly due to an intercalation leading to planar defects. The intercalation is found to be so dominant that the formation of defects due to neutron irradiation is extremely difficult to be determined with electron microscopy on the same areas before and after irradiation.
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2006
Atomic force microscopy investigations on swift heavy ion (200 MeV Au) irradiated surfaces of a high T c single crystal YBa 2 Cu 3 O 7 À d are presented. Results obtained revealed an ion-induced erosion/sputtering clearly confirming our earlier observation on grain boundary dominated thin films. Apart from sputtering, notable effects were seen with many defect structures like dikes/hillocks surrounded by craters, dikes, holes, pearl like structures and ripple formation of sub-micron undulations, all in one crystal. Results are discussed in the light of co-operative phenomena of material re-distribution mechanism related to mass transfer and crater formations.
Effect of gamma irradiation on pure and silver doped YBCO superconductor
Solid State Communications, 1993
Specimens of high-To superconductors, YBCO and (YBCO)I.96 Ag0.04, were irradiated with "r-rays up to an integrated dose of 77MR. Electrical resistance vs temperature and the X-ray diffraction patterns of the monolayers of the sample powders were obtained before and after the irradiations. The normal state resistance of the pure and Agdoped YBCO specimens gradually increase as the 'r-dose increases. The intensities of the X-ray diffraction peaks of the monolayers of the YBCO powders decrease with 'r-irradiation without significant change of diffraction angles or peak widths. The zero resistance transition temperature of the Ag-doped YBCO specimens decreases by about 0.5% with 'r-irradiation at 77 MR. These observations indicate that the high-T~ superconductor YBCO is quite sensitive to 'rirradiation but drastic lattice expansion does not occur up to a "r-dose of 77 MR.
The influence of Pb-ion irradiation on melt-textured YBa 2 Cu 3 O x crystals
Crystal Research and Technology, 2009
Melt-textured YBa 2 Cu 3 O x crystals have been irradiated along the c-axis with 208 Pb 56+ ions corresponding to dose matching fields, B Φ = 0.5 T and B Φ = 2.0 T. Magnetization measurements were conducted along the ab plane of the samples. The strength of pinning sites was investigated by measuring magnetization hysterisis and the saturation remanent magnetization M R at several temperatures. We have found that the pinning strength was considerably enhanced after irradiation at both doses. Interestingly, the pinning strength at a Pbion irradiation which corresponds to the dose matching field B Φ = 0.5 T, was found to be significantly larger than that at the dose matching field B Φ = 2.0 T at all temperatures.
Superconductor Science and Technology, 2008
The effect of 200 MeV Ag ion irradiation on the superconducting and normal state properties of the high-T c superconductor y O Cu YBa 7 3 2 (YBCO) is studied by in-situ temperature dependent resistance measurement. We show that irradiating YBCO thin films (~150 nm) at low temperature result into a softly defected region of about 85 nm radius due to swift heavy ion induced secondary electrons around the highly amorphized latent tracks of ~ 5 nm radius. This leads to decrease of T c at fluences three orders of magnitude less than the threshold fluence, where overlapping of tracks block supercurrent path. Due to their low energy (4.1 keV for 200 MeV Ag ion), the secondary electrons can induce point defects by inelastic process rather than by direct elastic collision.
Defect cascades produced by neutron irradiation in YBa2Cu3O7−δ
Physica C: Superconductivity, 1994
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