Enhanced supercurrent density in polycrystalline YBa2Cu3O7-δ at 77 K from calcium doping of grain boundaries

摘要: With the discovery of high-temperature superconductivity1, it seemed that vision superconducting power cables operating at boiling point liquid nitrogen (77 K) was close to realization. But soon found critical current density Jc supercurrents can pass through these polycrystalline materials without destroying superconductivity is remarkably small1,2. In many materials, suppressed grain boundaries2,3,4, by phenomena such as interface charging and bending electronic band structure5,6,7,8,9. Partial replacement (‘doping’) yttrium in YBa2Cu3O7-δ with calcium has been used increase grain-boundary values substantially, but only temperatures much lower than 77 K (ref. 9). Here we show preferentially overdoping boundaries, relative grains themselves, yields far exceed previously published values. Our results indicate doping a viable approach for producing practical, cost-effective cable liquid-nitrogen temperatures.