Abstract:Microstructure and magnetic hysteresis have been compared for two samples of the YBa2Cu3O7−δ (δ∼0) high-temperature superconductor, one unirradiated, and one irradiated with fast neutrons (E≳0.1 MeV) to a fluence of 3×1018 n/cm2. Notable changes in the microstructure include strain-induced contrast from regions 2–7 nm in size. An intrinsic critical current density (Jc) of 4.6×106 A/cm2 in zero field at 4 K has been determined from magnetic hysteresis measurements for the irradiated sample while 1.2×106 A/cm2 i… Show more
“…It has been demonstrated that fine-scale defects of a few nanometres can be artificially introduced into the HTS through neutron [68,69], proton [70], and heavy-ion 1711 irradiation. The J, of irradiated 123 single crystals has been shown to increase with irradiation fluence up to a certain maximum value before it decreases with further increase in fluence.…”
Section: Irradiation Damagementioning
confidence: 99%
“…The J, of irradiated 123 single crystals has been shown to increase with irradiation fluence up to a certain maximum value before it decreases with further increase in fluence. The defect structure is found to be small regions of vacancies created during irradiation, which may subsequently coalesce into defect clusters [69]. These regions are believed to possess a depressed superconducting order parameter with a characteristic spatial extent [70], and operate as effective flux-pinning centres due to their small dimensions.…”
Melt processing is the most prominent method utilized in the fabrication of bulk YBa2Cu30x(123) because of the superior transport and magnetic properties of this material. Due to the Y-diffusion-controlled growth mechanism of 123, the maximum allowable growth rate is sensitive to the size and distribution of the Y2BaCuOS precipitates. In addition, a slow cooling rate and a slow growth rate have to be employed to maintain the stability of the 123 planar growth front. Among the many melt-texturing methods and modifications, seeded directional solidification has the potential to produce long single-domained samples of large cross-sectional area with the strongly superconducting a-b planes aligned along the sample axis. Steady progress has also been achieved in flux-pinning enhancement through defect engineering. This includes the introduction and modification of defects such as twins, irradiation damage and second-phase inclusions. In particular, high-temperature mechanical deformation has been shown to be effective in increasing the dislocation density and results in improved Jc as well as reduced J, anisotropy.
“…It has been demonstrated that fine-scale defects of a few nanometres can be artificially introduced into the HTS through neutron [68,69], proton [70], and heavy-ion 1711 irradiation. The J, of irradiated 123 single crystals has been shown to increase with irradiation fluence up to a certain maximum value before it decreases with further increase in fluence.…”
Section: Irradiation Damagementioning
confidence: 99%
“…The J, of irradiated 123 single crystals has been shown to increase with irradiation fluence up to a certain maximum value before it decreases with further increase in fluence. The defect structure is found to be small regions of vacancies created during irradiation, which may subsequently coalesce into defect clusters [69]. These regions are believed to possess a depressed superconducting order parameter with a characteristic spatial extent [70], and operate as effective flux-pinning centres due to their small dimensions.…”
Melt processing is the most prominent method utilized in the fabrication of bulk YBa2Cu30x(123) because of the superior transport and magnetic properties of this material. Due to the Y-diffusion-controlled growth mechanism of 123, the maximum allowable growth rate is sensitive to the size and distribution of the Y2BaCuOS precipitates. In addition, a slow cooling rate and a slow growth rate have to be employed to maintain the stability of the 123 planar growth front. Among the many melt-texturing methods and modifications, seeded directional solidification has the potential to produce long single-domained samples of large cross-sectional area with the strongly superconducting a-b planes aligned along the sample axis. Steady progress has also been achieved in flux-pinning enhancement through defect engineering. This includes the introduction and modification of defects such as twins, irradiation damage and second-phase inclusions. In particular, high-temperature mechanical deformation has been shown to be effective in increasing the dislocation density and results in improved Jc as well as reduced J, anisotropy.
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