YBCO bulk superconductors were prepared by the solid state reaction andtop-seed-melt-textured growth (TSMTG) process. By using the AC susceptibility measurement, thecritical transition temperature T_c of samples is 91...YBCO bulk superconductors were prepared by the solid state reaction andtop-seed-melt-textured growth (TSMTG) process. By using the AC susceptibility measurement, thecritical transition temperature T_c of samples is 91.5 K for the highest value, and the transitionwidth ΔT_c is less than 1 K. The highest magnetization critical current densities J_c achieved 10~6A/cm^2 under 5 T at 10 K and 1.35X10^4 A/cm^2 under 2 T at 70 K (H//c), respectively. The resultscombining the SEM observation indicate that doping of Y211 particles is more effective in improvingthe growth quality of melt-textured YBCO superconductor and in reducing the micro-cracks ofspecimens. Doping of Y_2O_3 powder forms the rod-shaped Y211 particles, but doping of Y211 particlesdirectly to matrix materials forms the spherical Y211 particles mainly. Combining themicrostructures with J_c measurements shows that the interfaces are most important on flux bundlepinning, in which the gradient of free energy is larger than that of other place between the Y211particles and the Y123 matrix materials.展开更多
The infiltration-growth process was used as an alternative to conventional melt processing techniques for the preparation of bulk YBa2Cu3O7-x(Y123) with finely dispersed small size Y2BaCuO5(Y211) particles.Bulk YBCO s...The infiltration-growth process was used as an alternative to conventional melt processing techniques for the preparation of bulk YBa2Cu3O7-x(Y123) with finely dispersed small size Y2BaCuO5(Y211) particles.Bulk YBCO superconductors with uniformly distributed particles of micron-sized Y211 were prepared by the directional infiltration and growth(DIG).The microstructure changes of the Y211 particles at various stages of processing were studied.About 70% of Y211 particles are under 1 μm in the final sample.The different stopped growth mechanism of this material along the c axis and ab plane was discussed.Undercooling and viscosity lead to tanglesome thick boundary layer.So the Y123 growth along c axis is stopped.Yttrium lack in front of the ab plane is the main reason why the growth stops at this direction.展开更多
文摘YBCO bulk superconductors were prepared by the solid state reaction andtop-seed-melt-textured growth (TSMTG) process. By using the AC susceptibility measurement, thecritical transition temperature T_c of samples is 91.5 K for the highest value, and the transitionwidth ΔT_c is less than 1 K. The highest magnetization critical current densities J_c achieved 10~6A/cm^2 under 5 T at 10 K and 1.35X10^4 A/cm^2 under 2 T at 70 K (H//c), respectively. The resultscombining the SEM observation indicate that doping of Y211 particles is more effective in improvingthe growth quality of melt-textured YBCO superconductor and in reducing the micro-cracks ofspecimens. Doping of Y_2O_3 powder forms the rod-shaped Y211 particles, but doping of Y211 particlesdirectly to matrix materials forms the spherical Y211 particles mainly. Combining themicrostructures with J_c measurements shows that the interfaces are most important on flux bundlepinning, in which the gradient of free energy is larger than that of other place between the Y211particles and the Y123 matrix materials.
基金Project(50432050) supported by the National Natural Science Foundation of China
文摘The infiltration-growth process was used as an alternative to conventional melt processing techniques for the preparation of bulk YBa2Cu3O7-x(Y123) with finely dispersed small size Y2BaCuO5(Y211) particles.Bulk YBCO superconductors with uniformly distributed particles of micron-sized Y211 were prepared by the directional infiltration and growth(DIG).The microstructure changes of the Y211 particles at various stages of processing were studied.About 70% of Y211 particles are under 1 μm in the final sample.The different stopped growth mechanism of this material along the c axis and ab plane was discussed.Undercooling and viscosity lead to tanglesome thick boundary layer.So the Y123 growth along c axis is stopped.Yttrium lack in front of the ab plane is the main reason why the growth stops at this direction.
