REBCO mixtures with large difference in rare-earth ion size: superconducting properties of chemical solution deposition-grown Yb1-x Sm x Ba2Cu3O7- δ films.

Pablo Cayado,Bernhard Holzapfel,Jens Hänisch,Chuanbing Cai,Minjuan Li,Zhiyong Liu,Manuela Erbe

doi:10.1098/rsos.201257

Pablo Cayado, Bernhard Holzapfel + Show 5 more

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https://doi.org/10.1098/rsos.201257

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Abstract

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−xSmxBa2Cu3O7−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 Tc remains stable at approximately 90 K with Sm content up to x = 0.5 where Tc starts to increase towards the values of pure SmBCO films of approximately 95 K. On the other hand, the critical current densities Jc of the pure SmBCO films are the largest at 77 K, where the influence of a higher Tc 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.

Highlights

This article has been edited by the Royal Society of Chemistry, including the commissioning, peer review process and editorial aspects up to the point of acceptance
The critical current densities Jc of the pure SmBCO films are the largest at 77 K, where the influence of a higher Tc 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
The optimum crystallization temperatures of the different REBCO phases depend on the RE: they increase continuously from the REBCO compounds with smaller ions (YbBCO, ErBCO, YBCO) to those with bigger ions (EuBCO, SmBCO, NdBCO) reaching even more than 100°C of difference [22,23]

Summary

Introduction

This article has been edited by the Royal Society of Chemistry, including the commissioning, peer review process and editorial aspects up to the point of acceptance. The critical current densities Jc of the pure SmBCO films are the largest at 77 K, where the influence of a higher Tc 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. Several works reported the problems in preparing YbBCO films, leading, in general, to quite modest maximum critical temperatures Tc ∼ 90 K and self-field critical current densities, Jcsf, at 77 K of approximately 1 MA cm−2 [13–18] Another approach, and probably the most important one, for improving the superconducting properties of REBCO films is to increase the flux pinning. The synthesis of mixed compounds with a large difference in RE ion size may be more difficult and require a compromise between two optimal temperatures that might be more than 100°C apart

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