REACTION BETWEEN THE SUPERCONDUCTING OXIDE YBCO AND AMMONIUM BIFLUORIDE

The Fluorination of YBCO with NH5F2 proceeded as a tarnishing reaction. The reaction at 300 °C finished in 3 h consuming quantitatively one hydrogen fluoride in NH5F2. Fluorine was introduced into YBCO by using NH5F2 less than 0.5 mole for 1.0 mole YBCO to give the orthorhombic YBCFxOy which was not distinguished from the structure of the original YBCO. Superconducting properties of the orthorhombic YBCFxOy were not observed above liquid nitrogen temperature. Addition of more than 0.5 mole NH5F2 brought about the destruction of the YBCO structure to form a passive layer on the surface of YBCO powder particles and left unreacted YBCO inside. No fluorinated product showed a superconducting transition temperature higher than the 93 ± 1 K of the original YBCO. © 1990.