Isothermal electrical resistance relaxation studies were used to investigate the variation of microstructure and O diffusion behaviour in melt-texture grown YBCO bulk. Post-annealing below 550C for an as-grown sample does not seriously influence the grown defects except for O deficiency, and the variation of electric resistivity during oxygenation below 550C was attributed to the variation of O content in the Y123 matrix. Post-annealing at 930C reduced obviously the rate of the electric resistivity relaxation and the final value of the fully saturated electric resistivity due to the oxygenation at lower temperatures, which was attributed to the rearrangement of as-grown defects that were also partly annealed out, in the Y123 matrix at high temperature. The isothermal electric resistance relaxation due to O uptake at 350-500C for MTG-YBCO bulk after post-annealing at 930C was systematically investigated. The chemical diffusion parameters of O were estimated under certain assumptions. Compared with reported data for Y123, the diffusion activation energy was in the low value range and the apparent chemical diffusion coefficient was in the high value range for MTG-YBCO. This was all attributed to the grown defects and their variation in MTG-YBCO.

Electric Resistance Relaxation and Oxygen Diffusion in Melt-Texture Grown YBCO Bulk Post-Annealed at High Temperature. H.Zhang, H.Ye, K.Du, X.Y.Huang, Z.H.Wang: Semiconductor Science and Technology, 2002, 15, 1268-74