Recrystallization of Amorphous or Nanocrystalline NdBa₂Cu₃O_7-x and GdBa₂Cu₃O_7-x

Abstract

Using a novel melt-spinning technique, we have produced highly disordered NdBa₂Cu₃O_7-x and GdBa₂Cu₃O_y-x materials. Samples which were melt-spun in an O₂ environment consist of nanocrystals with the tetragonal REBa₂Cu₃O_7-x structure: samples which were processed in an N₂ environment consist of an amorphous matrix with small amounts of crystalline BaCu₂O₂, as shown by x-ray diffraction and electron microscopy. High temperature XRD studies indicate that the BaCu₂O₂ is eliminated during heating to 500°C in O₂ and that the REBa₂Cu₃O_7-x Phase recrystallizes directly from the amorphous matrix at temperatures below 800°C. Preliminary magnetization measurements show that higher temperature heat treatments are needed to restore superconductivity.