Growth Shape of YBa₂Cu₃O_6+x Single Crystal Fabricated by the Pulling Method

Abstract

Continuous growth of YBa₂Cu₃O_6+x(Y123) single crystal was achieved by the modified pulling method. The largest size of the Y123 single crystal obtained reaches 20 mm square under 1-atmosphere oxygen partial pressure and 24 mm square for the NdBa₂Cu₃O_6+x(Nd123) single crystal in air. Clear spiral growth patterns were observed on the crystal/liquid interface by AFM and STM. The growth model of the crystal was explained by the BCF model. The grown crystal was usually covered with a slow growth rate face such as a low index face, and the obtained crystal shape was cubic. Recently, we fabricated a round cornered Y123 single crystal by keeping the growth temperature around the peritectic temperature. A seed crystal was at first remelted at its corner, followed by growth of the round cornered crystal. Along the vertical axis, the crystal corner became wavy. The remelting process was explained by the free energy difference between the flat and square interfaces. Growth shapes of the round corner were explained by temperature-dependent growth rate anisotropy.