抄録
The phase transformation of REBa2Cu3O7-x (RE=Nd, Gd, Dy) was investigated using isothermal heat-treatment and continuous cooling in air. During continuous cooling, the REBa2Cu3O7-x (RE=123) superconducting phase with well-distributed REBa2Cu3O7-x (RE=211) was obtained at a cooling rate of 0.001°C /s. Single phase RE-123 (Nd, Gd, Dy) was stable at 1050°C, 1000°C, and 950°C during isothermal heat-treatment, respectively. Above these temperatures the RE-211 phase existed within the RE-123 grains. The RE-123, RE-211, BaCu2O2, and CuO phases coexisted at 50°C below the partial melting temperature for each respective rare-earth RE-123. The variations in the phase transformation and lattice parameters on the rare-earth elements were explained by the different ionic radiis of the elements. The superconducting properties of each specimen heat-treated at the optimum condition were compared with the magnetic characteristics.
