Embedding of nanoparticles as flux pinning sites in superconducting samples

Crystallographic orientations of thin films and bulk, melt-textured YBa₂Cu₃O_x high-T_c superconductors with embedded Y₂Ba₄CuMO_x (M = Nb, Zr, Ag) nanoparticles are studied by electron backscatter diffraction. The Y ₂BaCuO₅ particles exhibit no preferred orientation but have a strong negative influence on the matrix orientation. In contrast, the nanoparticles are not disturbing the texture of the YBCO matrix. For the bulk samples, depending on the preparation route, a different particle orientation with respect to the matrix is obtained. Untextured M-2411 nanoparticles are formed by solid state reaction during the melt process by adding oxides (Nb ₂O₅ or Y₂O₃) to the precursor powder. Pre-formed Y₂Ba₄CuMO_x particles added to the precursor in the form of pre-reacted nanopowder, exhibit a dominant single orientation related to the surrounding YBCO matrix. In the case of thin films prepared using laser ablation with a bulk YBCO sample with embedded nanoparticles as a target, the nanoparticles are transferred into the thin film, but the transferred M-2411 particles are found to be randomly oriented. Nevertheless, these films exhibit increased flux pinning properties.