Growth and Characterization of High T. Superconductor Single Crystals

Single crystals of oxide superconductor (ErBa 2 Cu 3 O 7−δ ) were grown from a liquid phase using an excess CuO+BaO as a flux. The crystals were square thin plates (3×3×0.1 mm 3 ) with large (001) faces on which various kinds of growth layers were developed including growth spirals. There was a certain correlation between Tc and the twinning. The measurements of Tc showed a large scatter in the value of Tc ranging from 65 to 90 K, in spite of a prolonged annealing and slow cooling in air or oxygen atmosphere. However, we found out for the first time a method to improve Tc by treating the solidified ingot in molten CrO 3 . It turned out that the value of Tc before this treatment was improved to the extent of 85 to 92 K