YBaCuO thick films on planar and curved technical substrates

For high-current applications, homogeneous well-textured high-temperature-superconducting Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBaCuO) films on technical ceramic or metallic substrates are required. The ion-beam-assisted deposition (IBAD) of yttria-stabilized zirconia (YSZ) buffer layers, which serve as templates for the YBaCuO, was extended to large planar areas (20 cm/spl times/20 cm) as well as curved or cylindrical (diameter /spl les/15 mm) substrates. For both types of substrates a pronounced in-plane alignment is observed. A deposition equipment is developed to grow high-quality YBaCuO films also on tubes by pulsed laser deposition (PLD), which is characterized by a high long-term stability both of the deposition rate and of the surface temperature of the growing film. Current densities up to 0.9/spl times/10/sup 6/ A cm/sup -2/ at 77 K in self fields are observed in films on planar Ni foils with biaxially aligned YSZ buffers (bi-YSZ). For the coating of long lengths of tubes and tapes a translation and a rotation of the samples are incorporated both in the buffer as well as in the YBaCuO-deposition process. Furthermore, the dependence of the critical transport current densities, J/sub c/, of the HTS layer on magnetic fields and on mechanical stresses are investigated.