REBCO mixtures with large difference in rare-earth ion size: superconducting properties of chemical solution deposition-grown Yb(1−x)Sm(x)Ba(2)Cu(3)O(7−)(δ) films

The main objective of this work was to study the superconducting properties of REBCO films with a mixture of rare-earth (RE) ions with large difference in ion size, in particular Sm(3+) and Yb(3+). These Yb(1−x)Sm(x)Ba(2)Cu(3)O(7−)(δ) films have been successfully prepared for the first time by chemical solution deposition following the extremely low-fluorine route, which allows reducing the fluorine content by 93% with respect to standard full trifluoroacetate solutions. On the one hand, critical temperature T(c) remains stable at approximately 90 K with Sm content up to x = 0.5 where T(c) starts to increase towards the values of pure SmBCO films of approximately 95 K. On the other hand, the critical current densities J(c) of the pure SmBCO films are the largest at 77 K, where the influence of a higher T(c) is very relevant, while at lower temperatures and low fields, the mixed films reach larger values. This demonstrates that mixing rare-earth elements RE in REBa(2)Cu(3)O(7−)(δ) causes a change in the pinning properties of the films and reveals the importance of selecting adequate REBCO compounds according to the temperature and magnetic field region of a desired application.