Disordered Oxygen Vacancies Research Articles

Vacuum annealing treatment effects on structure and superconductivity in RBa 2Cu 3O 7−δ and YBa 2−xK xCu 3O 7−δ

We report the effects of heat treatment in a very low pressure at 800°C on the structure and superconducting properties of RBa 2Cu 3O 7−δ R=Y, Nd and Eu, and YBa 2−xK xCu 3O 7−δ. These systems undergo an orthorhombic (and superconducting) to amorphous (and non superconducting) transition, caused by large oxygen losses ( δ = 1.3−1.8) and disordering of oxygen vacancies. Then by a controlled technique we restored the oxygen content to a value of δ = 0 and the orthorhombic crystal structure and superconductivity were fully recovered. The substitution of barium with potassium is reported for the first time. The recovered NdBa 2Cu 3O 7−δ ( δ = 0.7) is superconducting with T C = 89 K.

Annealing treatment effects on structure and superconductivity in Y1Ba2Cu3O9−x

We report the effects of heat treatment and ambient on the structure and superconducting properties of Y1Ba2Cu3O9−x. The structure undergoes an orthorhombic-to-tetragonal transition on heating at about 700 °C, caused by oxygen loss and disordering of oxygen vacancies on the copper plane between the barium layers. Heat treatments that promote maximum ordering of the oxygen vacancies result in superior superconducting properties.