High-quality single domain (Sm0.5Eu0.5)Ba2Cu3O7-δ superconductors were grown in air with a thermal gradient. We found that the substitution of Ba by rare earth (RE) elements was considerably suppressed when the growth rate is large. Enhanced superconducting properties were obtained by further controlling initial compositions and combining a post-annealing in Ar. The crystals exhibited a high Tc value of 95 K with a sharp superconducting transition, and a well-developed secondary peak effect in the Jc-B curve at 77 K. TEM observation revealed that the nano-sized chemical variation between RE and Ba provided robust flux pinning.
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