Addition of alternate phase nanoparticle dispersions to enhance flux pinning of Y-Ba-Cu-O thin films

Nanoparticle dispersions of various phases were added to YBa₂Cu₃O_7-x (YBCO or 123) thin films by multilayer pulsed laser deposition, to determine their effect on flux pinning. The different pinning materials examined include Y₂BaCuO₅ (Y211 or green-phase), La₂BaCuO₅ (La211 or brown-phase), Y₂O₃, CeO₂, and MgO, with lattice constant mismatches varying from 0.5% to 12% with respect to YBCO. Y211 and Y₂O₃ provided significant pinning increases at temperatures of 65 K and 77 K, however other phases provided enhancements only at 65 K (for CeO₂ and La211) for limited range of applied field strengths. An interesting correlation between T_c transition widths and pinning strengths was observed. The additions produced markedly different nanoparticle and film microstructures, as well as superconducting properties.