PRODUCTION OF SINGLE CRYSTAL OF OXIDE SUPERCONDUCTOR AND METHOD FOR CONTROLLING SUPERCONDUCTIVITY TRANSITION TEMPERATURE

摘要

PURPOSE:To obtain a high-quality single crystal of a Tl-contg. oxide superconductor having a sufficiently large size by mixing powder having a specified compsn. consisting of the oxides of Tl, Ba, Ca and Cu with KCl and/or NaCl as a flux, melting and slowly cooling the powdery mixture under specified conditions. CONSTITUTION:A powdery mixture having a compsn. represented by a formula Tl2O3+2BaO+(n-1)CaO+nCuO+x[(1-y)KCl+yNaCl] or a formula Tl2Ba2Can-1 Cun-O4+2n+x[(1-y)KCl+yNaCl] is melted at 700-950 deg.C and slowly cooled at =20 deg.C/hr rate to obtain a single crystal of an oxide superconductor represented by a formula Tl2Ba2Can-1CunO4+2n. In the formula, (n) is 2 or 3, 3=x=500 and 0=y=1. The superconductivity transition temp. of the superconductor is controlled by heat-treating the single crystal at 300-600 deg.C in oxygen under =400atm pressure.