Tuning the top-seeded melt growth of REBCO single-domain superconducting bulks by a pyramid-like buffer stack

Abstract

In this contribution, the usage of a pyramid-like buffer stack for optimization of the top-seeded melt growth process of GdBCO (GdBa 2 Cu 3 O 7-δ ) single-domain superconductors is demonstrated. The process was optimized by the addition of SmBCO into GdBCO/Ag into the buffer precursor powder, which effectively increased the peritectic temperature of the final mixed powder in the pyramid-like buffer stack. As such, this approach can be also used for other REBCO systems by selecting rare earth with a higher peritectic temperature and adding it to the buffer pellets. The thermal behavior of the powders was studied by STA. This enables fast and effective crystal growth through the buffer stack and the formation of large effective seeds. This approach also allows for reliable and precise tuning of growth angle and together with effective seed size facilitates tuning of a - b to c sector ratio. The phase composition of precursors and prepared bulks were studied by XRD. The microstructure was also studied by SEM and OM in detail. Subsequently, levitation force and trapped field were measured. Results confirmed that the addition of at least a single buffer pellet improved the melt growth process significantly by acting as a large effective seed. Superconducting properties of the samples grown by pyramid-like buffer stack are superior in comparison to reference TSMG samples.