REBCO mixtures with large difference in rare-earth ion size: superconducting properties of chemical solution deposition-grown Yb1-x Sm x Ba2Cu3O7- 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 Sm3+ and Yb3+. These Yb1-x Sm x Ba2Cu3O7- 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 REBa2Cu3O7- 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.