The Performance of the Two-Seeded GdBCO Superconductor Bulk with the Buffer by the Modified TSMG Method

The multiseeding technique is a method to grow large-sized REBa(2)Cu(3)O(7−δ) (REBCO, where RE is a rare earth element) high temperature superconducting bulks. However, due to the existence of grain boundaries between seed crystals, the superconducting properties of bulks are not always better than those of single grain bulks. In order to improve the superconducting properties caused by grain boundaries, we introduced buffer layers with a diameter of 6 mm in the growth of GdBCO bulks. Using the modified top-seeded melt texture growth method (TSMG), that is, YBa(2)Cu(3)O(7−δ) (Y123) as the liquid phase source, two GdBCO superconducting bulks with buffer layers with a diameter of 25 mm and a thickness of 12 mm were successfully prepared. The seed crystal arrangement of two GdBCO bulks with a distance of 12 mm were (100/100) and (110/110), respectively. The trapped field of the GdBCO superconductor bulks exhibited two peaks. The maximum peaks of superconductor bulk S(A) (100/100) were 0.30 T and 0.23 T, and the maximum peaks of superconductor bulk S(B) (110/110) were 0.35 T and 0.29 T. The critical transition temperature remained between 94 K and 96 K, with superior superconducting properties. The maximum J(C, self-field) of S(A) appeared in specimen b5, which was 4.5 × 10(4) A/cm(2). Compared with S(A), the J(C) value of S(B) had obvious advantages in a low magnetic field, medium magnetic field and high magnetic field. The maximum J(C, self-field) value appeared in specimen b2, which was 4.65 × 10(4) A/cm(2). At the same time, it showed an obvious second peak effect, which was attributed to Gd/Ba substitution. Liquid phase source Y123 increased the concentration of the Gd solute dissolved from Gd211 particles, reduced the size of Gd211 particles and optimized J(C). For S(A) and S(B) under the joint action of the buffer and the Y123 liquid source, except for the contribution of Gd211 particles to be the magnetic flux pinning center with the improvement of J(C), the pores also played a positive role in improving the local J(C). More residual melts and impurity phases were observed in S(A) than in S(B), which had a negative impact on the superconducting properties. Thus, S(B) exhibited a better trapped field and J(C).