MICROSTRUCTURAL STUDY OF MELT-PROCESSED YBA2CU3O7-DELTA THICK-FILMS ON YTTRIA-STABILIZED ZIRCONIA

The microstructure of high T(c) superconducting thick films of YBa2Cu3O7-delta screen printed on yttria-stabilized zirconia has been studied by transmission electron microscopy. Specimens were specially prepared to allow the examination of the film-substrate interfacial reaction zone near the substrate. It is found that the thick films are mainly aligned with the c axis of the YBa2Cu3O7-delta Crystals perpendicular to the substrate plane and contain numerous Y2BaCuO5 particles with an average size of about 1 mum. Grain boundaries have been observed showing coherence between two grains sharing the same orientation of their a or b planes, but are misoriented by a tilting of the c axis of 5-degrees-10-degrees. High-angle grain boundaries have also been observed, sometimes decorated by a thin amorphous phase. Many interfacial defects are revealed in the vicinity of the Y2BaCuO5 particles, in particular when the beam direction is close to the a or b axis. Frequently, a- or b- oriented grains also show internal low-angle grain boundaries, and cracks along their basal planes. Both CuO and Cu-rich BaZrO3 interdiffusion phases have been revealed at the substrate-superconductor interface.