Single Y123 Research Articles

Effects of Y2O3 additions on the oxygen diffusion in top-seeded melt growth processed YBa2Cu3O7−y superconductors

To understand the effect of Y2BaCuO5 (Y211)/YBa2Cu3O7−y (Y123) interfaces on the oxygen diffusion in single grain YBa2Cu3O7−y superconductors, single grain Y123 superconductors with 0.05 and 0.3moles of Y2O3 additions were fabricated by a top-seeded melt growth (TSMG) process. Y123 compacts with Y2O3 additions were subjected to melt growth heating cycles with a cooling rate of 1°C/h through a peritectic temperature (1015°C) and then annealed at 450°C for 200h in flowing oxygen. The superconducting temperature (Tc) and critical current density (Jc) were estimated for the three different regions (top surface (s), intermediate (i) and center (c)) of samples. The amount of Y211/Y123 interface area in single grain Y123 superconductors was successfully controlled by Y2O3 additions. The Tc values of s regions were higher than those of i and c regions, which indicates the presence of more oxygen at the sample surfaces. In addition, the Tc values of i and c regions of the Y123 sample with 0.3mole Y2O3 addition were higher than those of the same regions of the Y123 sample with 0.05mole Y2O3 addition due to the promoted oxygen diffusion through Y211/Y123 interfaces and other related defects. In spite of the promoted oxygen diffusion by Y2O3 addition, the large Tc difference among the regions still existed, which suggests sluggish oxygen diffusion into single Y123 grains.

Melt-textured YBCO superconducting tube for magnetic shielding

Melt-textured YBCO superconducting tube with a wall thickness of about 1 mm was prepared by infiltration and growth process; a method leads to the near-net shape fabrication and the refinement of Y-211 inclusions. The driving force for the liquid infiltration of this process is either capillary force or a chemical potential. Single Y-123 grains with the size of 5 mm were observed. The ambient noise measurements showed that the shielding factor of the melt-textured tube is one order of magnitude higher than that of comparable sintered tube within the frequency range from 1 to 200 Hz.

Fabrication of a good-quality single grain YBCO sample through the control of seed crystals

We investigated the growth mode of YBa/sub 2/Cu/sub 3/O/sub 7-y/ (Y123) grains and its effect on the levitation forces and trapped magnetic field of top-seeded melt processed YBCO samples. When a slab-like Sm-seed was used, undesirable subsidiary Y123 grains were formed, while the formation of the subsidiary Y123 grains was suppressed and a nearly single Y123 grain grew when a thick and wide seed was used. The formation of the subsidiary Y123 grains decreased the levitation forces and trapped magnetic field, due to the presence of grain boundaries with weak link characteristics.