Grain growth in the GdBa2Cu307-g high Tcsuperconductor was investigated. The composition Gd1.09Ba1.91Cu307-8 within the solid solubility region, was selected for the present grain growth study. Differential thermal analysis did not reveal any thermal event except the incongruent melting point, which is indicative of the absence of a liquid second phase during grain growth. The final densities of isothermally annealed samples ranged from 91.3% to 93.7% of theoretical density. The microstructure observation showed a greater grain aspect ratio in this material than in YBa2Cu307-δ. The average grain aspect ratio was about 4.7. A very low grain growth exponent of 0.07 was found in the isothermal annealing temperature range from 965 °C to 1020 °C. By comparison with the results on the YBa2Cu307-δ system previously reported, it was concluded that the grain growth kinetics in these materials are strongly controlled by the anisotropy of the grain boundary energy. The activation energy of grain growth was calculated to be about 77 kJ/mole.
Bibliographical noteFunding Information:
The authors would like to thank Dr. Hayne Palmour III and Dr. D. Haase for valuable discussions. The authors also thank Dr. J. L. Routbort in the Argonne National Laboratory for the provision of some activation energy data. The experimental assistance from Ms. D. Readier is appreciated. This work was supported by a grant from the Office of Basic Energy Science, Department of Energy, under Grant No. DE-FG05-88ER45359. Further financial support was received through the subcontract No. 87X-SG688V from Martin Marietta Energy Systems, Department of Energy, ORNL, HTSC Pilot Center.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering