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

Abstract

In this work, for the first time, we report a strengthened superheating effect caused by a buffering YBa2Cu3Oy (Y123 or YBCO) layer in a Nd1+xBa2−xCu3O7−y (Nd123 or NdBCO) thin film with a MgO substrate (i.e., NdBCO/YBCO/MgO thin film). In 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 the seed and under a maximum processing temperature (Tmax) of up to 1120 °C, we succeeded in growing various RE1+xBa2−xCu3O7−y (REBCO, RE = Gd, Sm, Nd, RE refers to rare elements) bulk superconductors. Pole figure (x-ray Φ-scan) measurement reveals that the NdBCO/YBCO/MgO film has better in-plane alignment than 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 Tmax in the MT process, the NdBCO/YBCO/MgO film is beneficial to the growth of bulk superconductors in two aspects: (1) broad application for REBCO materials of high peritectic temperature (Tp); (2) effective suppression against heterogeneous nucleation, which is of great assistance in growing large and high-performance REBCO crystals.