Abstract
The crystals of high-Tc oxide-superconductors YBCO are grown from the melt at higher temperatures. It is quite disadvantageous that the melt reacts with the crucibles in contact and contaminates the crystals. For the purpose to grow pure crystals a self-sustaining Verneuil method by laser-heating is examined. Unfortunately the oxide superconductors do not grow congruently from the melt. Therefore, further heat treatment is necessary to recover High-Tc phases.
As for YBCO crystals the boule is capped with a melt in excess of BaCu2O3 where the target crystals grow. This is a flux method in principle. The finished boule is heated at 910°C to melt away the flux to take out crystals. With an interference contrast microscope, it is confirmed that the crystal has grown by step growth process. The steps are rather heavily bunched. The domain structures have no correlation with the step structures. This suggests that the crystal growth is regular, while the domains are formed at the phase transition from the tetragonal to the orthorhombic phase after the crystal growth.
