YBCO-buffered NdBCO film with higher thermal stability in seeding REBCO growth

Abstract

In this work, we report a strengthened superheating effect caused by a buffering YBa 2 Cu 3 O y (Y123 or YBCO) layer in the Nd 1+x Ba 2-x Cu 3 O 7-y (Nd123 or NdBCO) thin film with MgO substrate (i.e., NdBCO/YBCO/MgO thin film). In the cold-seeding melt-textured (MT) growth, the NdBCO/YBCO/MgO film presented an even higher superheating level, about 20 °C higher than that of non-buffered NdBCO film (i.e., NdBCO/MgO film). Using this NdBCO/YBCO/MgO film as seeds and undergoing a maximum processing temperature (T max ) up to 1120 °C, we succeeded in growing various RE 1+x Ba 2-x Cu 3 O 7-y (REBCO, RE=rare elements) bulk superconductors, including Gd 1+x Ba 2-x Cu 3 O 7-y (GdBCO), Sm 1+x Ba 2-x Cu 3 O 7-y (SmBCO) and NdBCO that have high peritectic temperatures (T p ). The pole figure (X-Ray Φ-scan) measurement reveals that the NdBCO/YBCO/MgO film has better in-plane 2 alignment than the NdBCO/MgO film, indicating that the induced intermediate layer improves the crystallinity of the NdBCO film, which could be the main origin of the enhanced thermal stability. In short, possessing higher thermal stability and enduring a higher T max in the MT process, the NdBCO/YBCO/MgO film is beneficial to the growth of bulk superconductors in two aspects: (1) broad application for high-T p REBCO materials; (2) effective suppression against heterogeneous nucleation, which is of great assistance in growing large and high-performance REBCO crystals.

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

“…For the first time, Xu HH et al applied an NdBCO/YBCO/MgO thin film as a cold seed to induce homo-epitaxy, and the full growth of a single-grain NdBCO crystal without the Ag addition was gained (16 mm in diameter) [114]. Remarkably, this NdBCO/YBCO/MgO film seed has endured the T max of 1117°C for 1.5 h, which is about 20°C higher than the T max ($1098°C) that NdBCO/MgO thin film could survive [115].…”

“…Both together supply the yttrium solute in the crystal growth stage, leading to a high supersaturation status in the melt. In such a growth process, REBCO (RE = Y and rare earth element) film-seeds are applicable to effectively induce the growth of large-sized and high-performance REBCO bulks due to both intrinsically high superheating capacity and extrinsically high supersaturated melt [114,116,134,135].…”

“…X-ray pole figure of: (a) NdBCO/MgO thin film; (b) NdBCO/YBCO/MgO thin film with a 25-nm YBCO buffer layer[114].…”

Two-layer batch-process of YBa2Cu3Ox bulk superconductors induced by NdBa2Cu3Ox film-seeds

“…15 Because this novel film was demonstrated to have a tolerance for T max up to 1120 C, it is certainly beneficial to use it in a batch process of MT growth. On the other hand, apart from the tolerance for T max , the tolerance for the holding time is another key indicator of thermal stability of thin films, which is also crucial for the MT bulk growth.…”

Recycling failed bulk YBCO superconductors using the NdBCO/YBCO/MgO film-seeded top-seeded melt growth method

“…[8][9][10][11][12] In the MT growth process, REBCO film seeds demonstrated their great capacity over other seed materials in enduring higher T max , e.g., the tolerable T max is around 1100 C for the NdBCO film 10,11 and 1120 C for the YBCO-buffered NdBCO film, 12 respectively. This advantage of the film seeds is particularly helpful for recycling the failed REBCO bulks, since the solid REBCO in the bulks is more likely to completely decompose at a higher T max .…”