RE BCO 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 RE BCO 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 RE Ba ₂ Cu ₃ O _{7- δ} causes a change in the pinning properties of the films and reveals the importance of selecting adequate RE BCO compounds according to the temperature and magnetic field region of a desired application.
Competing Interests: We declare we have no competing interests.
(© 2020 The Authors.)