Abstract
Effects of annealing treatments on T-c of Ni-substituted YBa2Cu3O7-delta a have been studied. Ceramic samples of YBa2Cu3-xNixO7-delta (x = 0.00, 0.02, 0.05, and 0.10) prepared in l-atm oxygen atmosphere were annealed at 800-1000 degrees C in various atmospheres with different oxygen partial pressures, and subsequently oxygenated below 550 degrees C. The lower the oxygen partial pressure, the lower the T-c. For the samples with a fixed x but different T-c's, no appreciable difference in lattice parameters and oxygen contents was observed. The results clearly indicate that the T-c of Ni-substituted YBa2Cu3O7-delta can be controlled by changing the oxygen partial pressure during annealing treatment. It is likely that the distribution of Ni atoms between the chain and plane sites can be altered by the annealing treatment.