Seed-Size Effect on the Growth and Superconducting Performance of YBCO Single-Grain Bulks

Abstract

Exploiting their distinguished merits of commercial availability, large size, and extremely high thermal stability, a series of NdBCO film-seeds were employed to study their size effects on the YBCO bulks by melt-growth. First, our findings show that the nucleation range is almost the same with the variation of the seed size and that the effective contact area of the seed with the molten pellet is smaller than the seed area, which can be explained by the liquid's wettability and its surface energy. Moreover, induced by the large-sized seed, the YBCO grain has the highest a-axis growth rate, R a , because of a double mode of thermally driven plus seed-induced growth, leading to a larger c-GS (c-growth sector). Finally, the levitation force of bulks were proven to possess an ascending and subsequently descending tendency with increasing the seed size, which is clarified by the enlargement of c-GS in competition with enhancement of pore density of bulks. In short, the results from this work are helpful to understand the crystallization mechanism and to gain the optimal superconductivity property with a reasonable seed size.

Synthesis of Nanocrystalline BaCeO3 by Oxalate Coprecipitation for YBa2Cu3O7 Bulk Superconductors

“…The prepared BaCeO 3 powder, in amount corresponding to 1 wt% CeO 2 , was added to starting charge of powders with nominal composition Y 1.5 Ba 2 Cu 3 O x . After mixing, milling in a friction mill and pressing into cylindrical pellets of 20 mm in diameter, YBCO BSS was fabricated by the top seeded melt growth (TSMG) process [13,14]. Both the size and shape of BaCeO 3 crystallites, as well as microstructure of YBCO crystal were studied by scanning electron microscopy (SEM) by MIRA3 TESCAN microscope.…”

Film thermal stability correlation with seeding modes in the growth of YBa2Cu3O7−δcrystals

“…The wettability is very sensitive to the change in the liquid property. So the shift in the precursor constitution from A to B causes a decrease in the Y content in the liquid (low supersaturation), further weakening the liquid wettability status (Li et al, 2015) with respect to the Nd123 film.…”

Peritectic melting of thin films, superheating and applications in growth of REBCO superconductors

“…Schematic illustration showing virtual growth modes of Y-123 c-axis oriented crystals induced by a small and a large seed, respectively. The a-GS and the c-GS are represented as blue and green entities, respectively [151]. and most importantly, following a rapid completion of the growth of four small a-GS by applying LSS, the YBCO crystal with large c-GS and high performance is possible to be achieved.…”

“…The main advantages of the use of NdBCO films are their high superheating capacity (enduring T max up to 1120°C), and conveniently commercial availability of large-sized film-seeds with reliable high quality. As a result, a series of seeds (2 ⁄ 2 mm 2 , 4 ⁄ 4 mm 2 , 7 ⁄ 7 mm 2 and 9 ⁄ 9 mm 2 ) were applied to study the effects of the seed size on the growth of YBCO crystals [151]. As shown in Fig.…”

“…More recently, significant progresses have been made in the superheating mechanism and applications of REBCO thin films with free surfaces. Top and side views of YBCO grown c-axis oriented crystals induced by NdBCO film seeds with different sizes of 2 ⁄ 2 mm 2 , 4 ⁄ 4 mm 2 , 7 ⁄ 7 mm 2 and 9 ⁄ 9 mm 2 , respectively [151].…”