Melt-spin processing of YBa₂Cu₃O_7−x

Abstract

We introduce a novel containerless melt-spin processing technique for YBa2Cu3O7−x using prereacted oxide powders that are rapidly melted and subsequentially quenched in a controlled atmosphere. This results in flakes with typical dimensions of 3000 × 150 × 15 μm3. Powder XRD indicates that all samples contain Y2O3, but that the Ba–Cu–O phases present depend on the processing parameters. SEM and TEM studies show these phases are finely dispersed: the typical grain size for Y2O3 is 1–2 μm, and for the Ba–Cu–O phases it is <0.5 μm.

Recrystallization of amorphous and nanocrystalline NdBa/sub 2/Cu/sub 3/O/sub 7-x/ and GdBa/sub 2/Cu/sub 3/O/sub 7-x/

“…As for the second point, Nd123, with a relatively low liquidus temperature (due to a low melting point for the RE2O3) and a high decomposition temperature for the RE123 phase, should naturally require less undercooling to allow the formation of a highly disordered material. Y123, with an even wider spread between the liquidus and solidus than Gd123, has not been seen to form any significant amount of amorphous material under similar processing conditions [4].…”

“…We have developed a novel rapid quench melt-spinning processing technique described in detail elsewhere [4]. Our techque has a unique combination of advantages not available using previous techniques: there is no crucible to introduce impurities, the chill wheel provides extremely high quench rates, and control of the oxygen partial pressure allows variations in the as-quenched material.…”

“…Using this melt-spinning technique, we have produced highly disordered NdBazCusO7., (Nd123) and GdBazCu307., (Gd123) materials. Previous work with the YBa2C~307-~ (Y123) system resulted in material with microcrystalline Y2O3 in a Ba-Cu-0 matrix [4]. Nd123 and Gd123 were chosen for this study because of the systematic decrease in liquidus temperature and increase in decomposition temperature seen as one moves toward the larger RE elements [5].…”