Epitaxial superconducting GdBa2Cu3O7−δ /Gd2O3 nanocomposite thin films from advanced low-fluorine solutions

Abstract

We have employed the CSD method to synthesize GdBCO and GdBCO-Gd2O3 nanocomposite 250-300 nm thin films. For this we have designed a new low-fluorine solution never used before in the synthesis of GdBCO thin films that allows us to reduce the HF release by 80% and increase the reproducibility of the pyrolysis process. The growth of these thin films required a new thermal process to be designed, which we refer to as 'flash-heating', where the heating rate is extremely fast (~600 °C min−1). The structure and the superconducting properties of the pristine GdBCO films are excellent, showing a (00 l) epitaxial orientation of the GdBCO grains and T c values that reach 92.8 K, which means an enhancement of more than 1 K with respect to standard YBCO films. The calculated J c inside the grains (${J}_{{\rm{c}}}^{{\rm{G}}}$) also presents remarkable values: ${J}_{{\rm{c}}}^{{\rm{G}}}$(5 K) ~ 40 MA cm−2 and ${J}_{{\rm{c}}}^{{\rm{G}}}$(77 K) ~ 3.3 MA cm−2. Finally, the GdBCO-Gd2O3 nanocomposites films, with a 20% mol of Gd2O3, exhibit superior superconducting properties and pinning performances with respect to GdBCO pristine films