YBCO films with different levels of excess yttrium were prepared on single-crystal LaAlO 3 with metal-organic deposition using trifluoroacetates (TFA-MOD). X-ray diffraction and transmission electron microscope measurements revealed excess yttrium in YBCO in the form of nanoscale Y 2 O 3 with (400) preferred orientation. The field dependence of J c demonstrated that YBCO films with Y 2 O 3 doping had enhanced J c in comparison with stoichiometric YBCO films in the magnetic fields. We think the reason for this is that the Y 2 O 3 nanoparticles act as pinning centres. YBCO films with 60% yttrium excess display 43% increased J c compared to stoichiometric YBCO films at a magnetic field of 1 T.
Solution deposition is a promising method for YBCO coated conductor fabrication. We developed a new fluorine-reduced 'metal-organic deposition using trifluoroacetates' (TFA-MOD) method with copper acetate as one of the starting materials. Using the fluorine-reduced TFA-MOD method, we were able to get high performance YBCO films with good out-of-plane and in-plane orientations within a shortened calcining time, which was reduced by at least 4 h in comparison with that for the normal TFA-MOD process. Good superconducting properties, with J c of 2 MA cm −2 at 77 K and T c of 88.3 K ( T c = 0.9 K), have been obtained for 350 nm epitaxial YBCO thin films on LaAlO 3 single-crystal substrates. Owing to the low price of copper acetate and the shorter calcining time, fluorine-reduced TFA-MOD is a very effective and cost-cutting process.
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