Method of manufacture of single phase ceramic superconductors
US5401712A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 18, 1992 |
| Grant date | Mar 28, 1995 |
| Priority date | — |
| Expiry date | Sep 18, 2012 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S505/782
Abstract
A ceramic superconductor is produced by close control of oxygen partial pressure during sintering of the material. The resulting microstructure of YBa.sub.2 Cu.sub.3 O.sub.x indicates that sintering kinetics are enhanced at reduced p(O.sub.2) and that because of second phase precipitates, grain growth is prevented. The density of specimens sintered at 910.degree. C. increased from 79 to 94% theoretical when p(O.sub.2) was decreased from 0.1 to 0.0001 MPa. The increase in density with decrease in p(O.sub.2) derives from enhanced sintering kinetics, due to increased defect concentration and decreased activation energy of the rate-controlling species undergoing diffusion. Sintering at 910.degree. C resulted in a fine-grain microstructure, with an average grain size of about 4 .mu.m. Post sintering annealing in a region of stability for the desired phase converts the second phases and limits grain growth. The method of pinning grain boundaries by small scale decompositive products and then annealing to convert its product to the desired phase can be used for other complex asides. Such a microstructure results in reduced microcracking, strengths as high as 230 MPa and high critical curr…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.