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A systematic investigation of superconducting multilayered films composed of alternating nanostructured YBa2Cu3O6+x (YBCO) and secondary phase BaZrO3 (BZO) layers is carried out. Detailed growth mechanism studies of these structures as well as superconducting properties in a wide temperature and magnetic field range are investigated by varying the thicknesses of layers grown by pulsed laser deposition. Structural analysis shows that multilayering changes clearly the growth mechanism of YBCO. Alternating thin BZO layers smoothen the film surface, create in-plane mosaic spread structure of the YBCO crystals, produce stress in the BZO interface region and moreover improve the out-of-plane alignment of YBCO. Magnetic measurements of superconducting properties demonstrate that the critical temperature decreases slightly when the thickness of the BZO layers increases relative to the YBCO layers. This indicates a growing strain effect at the layer interfaces. At the same time, critical current densities of multilayers in the whole used temperature and magnetic field range are increased to the same level as in conventionally BZO-doped YBCO films when very thin alternating YBCO/BZO layer structures are deposited. This thickness dependent result is explained by the dense flux pinning centre network in layered superconductors, giving the opportunity to increase the overall thickness of a film and further enhance the current-carrying capability.

We report the effect of 4 wt% BZO-doping in GdBCO thin films on (100) STO substrates with novel nanograined target materials deposited by pulsed laser deposition (PLD) method. X-ray diffraction, atomic force microscopy and magnetization measurements, which were made in particularly wide temperature and magnetic field range, were used to determine the structural and superconducting properties. The results were compared with ones of YBCO. The deposition temperature, s , is not very critical for GdBCO and it is found to be much lower in undoped and BZO-doped GdBCO than in YBCO. The BZO-doping of GdBCO enhanced the field dependence of critical current density, c , at low temperatures. Furthermore, BZO-doping enhances the accommodation field, , below 60 K being clearly higher at 10 K in doped GdBCO than in YBCO. The pinning mechanism in GdBCO was concluded to be similar to that of YBCO. Our results clearly show that undoped and BZO-doped nanophase GdBCO is a very promising target material for applications as well as for coated conductors.