YBCO/Nd2CuO4/NiO/Ni coated conductors fabricated by liquid phase epitaxy based techniques

Liquid phase epitaxy (LPE) has a great potential in producing low-cost, high-current, coated conductors due to its fast growth rate in excess of 1 μm min-1 and the capability of growing thick films up to 10 μm without degrading the structural perfection or Jc. The main problem for LPE is the chemical reaction between the films and substrates at elevated growth temperatures. Former efforts have been focused on the reduction of growth temperatures. This has been proved to be unsuccessful due to the limited degree of temperature reduction; reducing the growth temperature also reduces the solubility of YBCO in the liquid, making the growth even more difficult. An alternative solution to this problem is to search for a special buffer which is particularly resistant to the attack of the high-temperature liquid. We have recently developed a new buffer, Nd2CuO4, which was very stable in the cuprate solution at temperatures around 950 deg. C and therefore extremely useful for LPE. Initial growth of YBCO on Nd2CuO4 buffered, surface oxidized Ni substrates showed a sharp superconducting transition at 90 K and transport Jc over 105 A cm-2 (77 K). Although YBCO could be grown on Nd2CuO4 by LPE without any other intermediate seed layer, growth of Nd2CuO4 on both sides of the NiO/Ni substrate with 100% coverage was not easy and had a low success rate. Complete coverage of Nd2CuO4 buffer on the NiO/Ni substrates was the critical step to avoid Ni contamination and achieve a high Jc