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.

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High-quality and large YBa 2 Cu 3 O 7À (YBCO or Y123) single crystals are necessary for both fundamental studies and practical applications. The recently exploited modified melt growth (MMG) procedure realizes a high efficiency of growth and high purity of Y123. However, it was unexpectedly found that the thermal stability of the NdBa 2 Cu 3 O 7À (Nd123) film seed applied in MMG is greatly reduced owing to a change in the liquid property. In order to solve this problem, a new top-seeding mode, buried seeding, is developed to strengthen the film thermal stability, leading to a remarkable enhancement of endurable maximum processing temperature of over 30 K in low supersaturation. Furthermore, the correlation of the thermal stability of the film seed in melt growth with the liquid property and top-seeding modes is clarified. Most importantly, the buried-seeding mode was successfully applied in this work, opening a promising pathway for the effective growth of single crystals of other REBCO (RE = Nd, Sm, Gd) oxides (possessing a higher peritectic temperature than YBCO), as well as other functional oxides.

Study on peritectic reaction is a matter of significant importance in materials science, which generally involves in the solidification of most functional oxide materials, for example, the YBa2Cu3O7−δ (Y123) superconductor could be grown via a reaction of Y2BaCuO5 (Y211) + Liquid→Y123. Due to its crystallization characteristic, the growth of those materials does not entirely proceed, which severely impedes the development of industrialized process. Thus the realization of a complete peritectic reaction is an interesting issue for both theory and experiment. Here, we report an almost complete peritectic reaction occurring in the growth of YBa2(Cu1−xFex)3O7−δ crystals using modified melt‐growth. Our findings remarkably show that Y211 almost fully reacted with liquid to generate Y123, remaining approximately 1 vol%, evidently lower than that in the normal case. The nature of this unconventional phenomenon is clarified that the Fe‐doping elevates the nucleation barrier in the peritectic melting of Y123 and causes a massive homogeneous nucleation catastrophe, leading to nanosized and dispersive Y211 particles, which readily and almost fully dissolve in the subsequent peritectic solidification of Y123. Most importantly, the new conception derived from this work is promising for reviving other functional materials, which are disregarded due to their incomplete peritectic reactions.

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