The influence of fluorine addition on the crystal structure and electrical properties of a YBa2Cu3O7−δ oxide superconductor

The influence on crystal structure and electrical properties of fluorine ions replacing oxygen ions in the YBa2Cu3O7-δ lattice is observed by mixing BaF2 powder and calcining at 1193 K. Within a small limit, the increase of BaF2 addition gives a sharp rise to the lattice constant of the c-axis while excess addition over the limit causes almost no change in the lattice constant. This suggests that BaF2 dissolves in solid solution with the minute solubility limit which is estimated to be around x=0.15 in the form of YBa2Cu3O7-δFx. The zero-resistivity transition temperature is the highest at x=0.10.