BCO mixtures with large difference in rare-earth ion size: superconducting properties of chemical solution deposition-grown Yb Sm BaCuO films.

The main objective of this work was to study the superconducting properties of BCO films with a mixture of rare-earth () ions with large difference in ion size, in particular Sm and Yb. These Yb Sm BaCuO 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 remains stable at approximately 90 K with Sm content up to = 0.5 where starts to increase towards the values of pure SmBCO films of approximately 95 K. On the other hand, the critical current densities of the pure SmBCO films are the largest at 77 K, where the influence of a higher is very relevant, while at lower temperatures and low fields, the mixed films reach larger values. This demonstrates that mixing rare-earth elements in BaCuO causes a change in the pinning properties of the films and reveals the importance of selecting adequate BCO compounds according to the temperature and magnetic field region of a desired application.