Secondary phase particles in bulk, infiltration-growth processed YBCO investigated by transmission Kikuchi diffraction and TEM

We present results of the first application of the transmission Kikuchi diffraction (TKD) technique to bulk, infiltration growth (IG)-processed YBa₂Cu₃O_7-δ (YBCO) superconductors with embedded Y₂BaCuO₅(Y-211) nanoparticles. By means of focused ion-beam (FIB) milling, TEM slices were prepared from mechanically polished surfaces of bulk, IG-processed YBCO samples. The required optical transparency was reached by additional polishing the resulting surfaces using the FIB and Ar-ion milling. For TKD, the sample was mounted on a homebuilt sample holder in the SEM, which provides the required inclination for TKD. The improved spatial resolution of TKD enabled the investigation of the small Y-211 particles (diameter of about 60-210 nm) embedded in the superconducting YBCO matrix. The fabricated TEM slices further enable the application of transmission electron microscopy to the same sample sections. These tiny Y-211 particles embedded within the YBCO matrix are, together with their strain fields, directly responsible for the high irreversibility fields due to the effective flux pinning of the IG-processed samples.