Nanorod Self-Assembly in High J(c) YBa(2)Cu(3)O(7−x) Films with Ru-Based Double Perovskites

Many second phase additions to YBa(2)Cu(3)O(7−x) (YBCO) films, in particular those that self-assemble into aligned nanorod and nanoparticle structures, enhance performance in self and applied fields. Of particular interest for additions are Ba-containing perovskites that are compatible with YBCO. In this report, we discuss the addition of Ba(2)YRuO(6) to bulk and thick-film YBCO. Sub-micron, randomly oriented particles of this phase were found to form around grain boundaries and within YBCO grains in bulk sintered pellets. Within the limits of EDS, no Ru substitution into the YBCO was observed. Thick YBCO films were grown by pulsed laser deposition from a target consisting of YBa(2)Cu(3)O(y) with 5 and 2.5 mole percent additions of Ba(2)YRuO(6) and Y(2)O(3), respectively. Films with enhanced in-field performance contained aligned, self-assembled Ba(2)YRuO(6) nanorods and strained Y(2)O(3) nanoparticle layers. A 0.9 µm thick film was found to have a self-field critical current density (J(c)) of 5.1 MA/cm(2) with minimum J(c)(Θ, H=1T) of 0.75 MA/cm(2). Conversely, J(c) characteristics were similar to YBCO films without additions when these secondary phases formed as large, disordered phases within the film. A 2.3 µm thick film with such a distribution of secondary phases was found to have reduced self-field J(c) values of 3.4 MA/cm(2) at 75.5 K and J(c)(min, Θ, 1T) of 0.4 MA/cm(2).