Greatly Improved Trapped Magnetic Fields of REBCO Melt-Grown Bulks Through Reductive High-Temperature Post-Annealing

We investigated the effects of high-temperature post-annealing on magnetic field-trapping properties of REBa ₂ Cu ₃ O _y melt-grown bulks composed of a single c -growth domain prepared by the single-direction melt growth (SDMG) method. High-temperature post-annealing at 900 °C under moderately reductive atmosphere for readily oxygenated bulks greatly improved trapped fields with maintaining circular concentric distributions. Oxygen diffusion was found to be further accelerated after post-annealing as well. An enhancement ratio of the trapped field averaged over all bulks through this post-annealing was ∼40% in the present study. In particular, a DyBa ₂ Cu ₃ O _y bulk with 24.3 mm in diameter and 10.8 mm in thickness recorded a high trapped field of 1.09 T at 77 K.