Isothermal melting and continuous isothermal melt texturing of YBaCuO

A study of isothermal melt texturing, whereby the O/sub 2/ partial pressure dependence of the melting point of YBCO is exploited to substitute for the slow cooling and temperature gradient of the melt textured growth method, is presented. A melt pool is produced by lowering the O/sub 2/ partial pressure locally with a jet of Ar directed onto the center of a YBCO slab within an O/sub 2/-filled furnace, and its development is investigated as a function of temperature, Ar/O/sub 2/ ratio, and time. If the pool is allowed to cool slowly, a large grained microstructure is formed, with 123 crystals of around 1-mm average cross section. The critical current density is around 2000 A/cm/sup 2/ at 77 K (B=0 T). In a further set of experiments the jet is driven slowly across the surface, melting a track. When the jet moves sufficiently slowly, a large grained microstructure is formed by continuous, isothermal processing.<
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