OPTIMIZATION OF SINGLE-CRYSTAL PREPARATION OF BI2SR2CACU2OX SUPERCONDUCTOR BY THE TRAVELING SOLVENT FLOATING ZONE METHOD

Optimization of single crystal preparation of the Bi2.2(Sr, Ca)2.8Cu2.0Oysuperconductor by the travelling solvent floating zone method has been performed with the intention of obtaining large single crystals and improving the superconductive transition temperature, Tc. The composition ratio, Sr/Ca, and the oxygen partial pressure of growth atmosphere, Po2, were varied in the crystal growth. A single crystal typically obtained was a thin plate of the dimensions of 5 × 50 × 2 mm3. The thickness of the crystal was the largest in the crystal growth at Sr/Ca= 1.4, while no distinct change was observed in the resulting crystals in the range of 22-100 kPa. Electric and magnetic properties, the formal charge of copper ions and existence of ion defects are discussed. © 1990 IOP Publishing Ltd.