Y₂BaCuO₅buffer block as a diffusion barrier for samarium in top seeded melt growth processed YBa₂Cu₃O_{7 −y}superconductors using a SmBa₂Cu₃O_{7 −d}seed

Abstract

A Y2BaCuO5 buffer (Y211) block, as a diffusion barrier for samarium atoms of a top seeded melt growth (TSMG) processed YBa2Cu3O7 − y (Y123) superconductor using a SmBa2Cu3O7 − d (Sm123) seed, was examined in terms of the buffer thickness (t). Disc-type Y211 blocks with various t were inserted at the seed/compact interface and subjected to melt growth heating cycles. The superconducting transition temperature (Tc) and critical current density (Jc) were measured for the three different top surface regions: (1) the region just below the seeded Y211 buffer block, (2) the intermediate region between the buffer block and the sample edge, and (3) the sample edge. The Tc values of regions 1 and 2 of the samples without the buffer and with thin buffers were lower than that of region 3, and the superconducting transition widths were larger. As t was increased to 3 mm, the susceptibility curves of the three regions showed the same Tc of 90 K and sharp transitions. The Jc–B curves of regions 1 and 2 without a buffer and with thin buffers showed the peak effect due to the formation of Y1 − xSmxBa2Cu3Oz. The peak effect almost disappeared when t was increased to 3 mm. Y211 particles and the Y123 matrix in the buffer block acted as an effective samarium absorber by forming mixed rare-earth 211 particles and Y1 − xSmxBa2Cu3Oy. These results suggest that the Y211 buffer block technique can be applied to the fabrication of large single grain Y123 superconductors with a uniform Tc and Jc distribution on the top surfaces.

A Reliable Method for Recycling (RE)‐Ba‐Cu‐O (RE: Sm, Gd, Y) Bulk Superconductors

“…To improve the success rate of seeding, a buffering technique was adopted in YBCO, GdBCO‐Ag, and SmBCO‐Ag recycled process, for example, small pellets (referred to as buffer pellets) of mass 0.3 g and diameter 5 mm of (RE)BCO (without Ag 2 O) mixed powder were pressed uniaxially and placed on the top surface of each failed sample, as shown in Fig. (b), to aid the seeding process and to prevent contamination of the seeded pellets . A conventional NdBCO seed was then placed at the center of the top surface of each buffer pellet.…”

The use of buffer pellets to pseudo hot seed (RE)–Ba–Cu–O–(Ag) single grain bulk superconductors

“…Several authors, including Kim et al [14], Yao et al [10,15] and Zhou et al [16], have described a method in which a small pellet is inserted between the seed and green precursor bulk sample in order to inhibit the diffusion of harmful elements from the seed into the growing bulk sample [14,10]. This method may also be used to accommodate lattice mismatch between a MgO seed and the precursor pellet [16].…”

Influence of Sm and Yb Pollution on Superconducting Properties of YBCO Bulk Superconductors

“…Sm from the seed and Yb from the substrate were identied in concentrations 0.1 wt% and 0.25 wt%, respectively, practically in the whole sample volume. Contamination of YBCO samples by Sm has already been reported [6]. Dissolution of the Sm-123 seed used during TSMG melt processing of Y-123 was observed.…”