Single-domain Yba 2 Cu 3 O y thick films and fabrics prepared by an infiltration and growth process
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An infiltration and growth process has been developed to produce single-domain YBa2Cu3Oy(123) as thick films on various substrates or as self-supporting fabrics. Commercially available Y2O3 cloths of square woven or satin woven structure were infiltrated with liquid phases from a suitable source containing barium cuprates and copper oxides and subsequently converted into Y2BaCuO5(211) and -123 phases by a series of distinct peritectic reactions. Depending on the final form of 123, the Y2O3 cloth was either clamped firmly at corners to produce a self-supporting 123 fabric or placed on a suitable substrate to result in a thick film coating of 123. The source material for the liquid phase being in the form of solid blocks was placed at corners of the cloth in the case of free-standing 123 fabrics. In case of the thick film configuration the liquid phase powder was spread on the surface of the Y2O3 cloth. A small c-axis-oriented MgO or Nd(123) seed was used to generate an oriented 123 domain in the infiltrated fabric. The solidification process was optimized to transform the entire Y2O3 fabric into a single-domain 123. The microstructure of the single domain was optimized in terms of 211 size and content for high Jc. A detailed description of the process, the growth mechanism, the resulting microstructures was given, and basic superconducting properties of the new form of 123 are briefly discussed.
I. INTRODUCTION
Since the discovery of high-temperature superconductors, there has been enormous effort to realize practical devices using these materials. Unlike the low-Tc intermetallic alloys, these materials did not make their way readily into device applications due to their brittle ceramic nature. After an intense global research a few process techniques have emerged, which at least partly allow one to realize products made from these materials. For Bi-based materials, the various wire processing techniques, like e.g., the oxide-powder-in-tube (OPIT), have been developed for the fabrication of long length— up to few kilometers—wire, due to the possibility of crystallization of self-aligned grains at the Ag interface.1,2 In the case of the rare-earth 123 (REBa2Cu3Oy) family, although their superconducting properties at 77 K and in magnetic fields exceeding 1 T are superior to Bibased materials, the fabrication technologies for wire processing are still not mature. A variety of processing techniques have been developed to exploit this material in bulk and film forms with excellent superconducting properties. The various melt processing techniques melt textured growth (MTG), solid liquid melt growth (SLMG), quenched melt growth (QMG), zone melting, etc., particularly coupled with a seeding technique, J. Mater. Res., Vol. 16, No. 4, Apr 2001
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have been optimized to fabricate highly textured single domain bulk material in rod and disk shapes up to sizes of 10 cm.3–11 These single-domain materials are already finding their way into certain application areas like beari
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