1992 Volume 56 Issue 6 Pages 722-728
The Y-base high-TC oxide superconductors have been synthesized by an organic acid salt thermal decomposition process. This process allows the addition or substitution of other elements easily and quantitatively. The precursor powder less than 10 μm in diameter have been obtained by this process.
The effects of Ag addition and Zr substitution for Y on superconducting properties and structures of high-TC YBa2Cu3O7−x (123) oxide were studied. TC ’s of 92 K have been obtained after a relatively short sintering in the 123 specimen. The addition of 10∼30 mass%Ag decreases the optimum sintering temperature to achieve highest TC by ∼50°C. The 5 at%Zr substitution for Y produces much smaller 123 grains with uniform grain size. Both the Ag addition and the Zr substitution enhance the JC (77 K) of the 123 specimen by a factor of several. The refinement of 123 grains and the dispersion of fine Ag particles seem to attribute to the enhancement in JC.
Furthermore, effects of simultaneous substitution of Zr and addition of Ag were also studied. The decrease of optimum sintering temperature is observed like Ag-added 123 specimens. A JC (77 K) of 300 A/cm2 has been obtained after the sintering at 880°C for 4 h. The Zr substitution reduces the rapid decrease of JC by the prolonged sintering in the Ag-added specimen.
The X-ray diffraction analyses were performed on these specimens. The diffraction peaks of 123-phase and Ag are obtained in the Ag-added specimens, while those of 123-phase and orthorhombic ZrO2 are obtained in the Zr-substituted specimens.
