Long-term stability of ceramics in liquid lithium

Two candidate materials for insulating coatings in a lithium-cooled fusion reactor have been exposed to lithium in 1000 h isothermal tests from 400-80 0 degreesC to determine their maximum compatibility temperature. Bulk sampl es of AIN + 5 wt%Y2O3 showed significant mass loss at 600 degreesC and high er temperatures. The amount of attack was reduced when AIN + 0.04 wt%Y was tested. Characterization by Auger spectroscopy of a AIN + 0.04 wt%Y specime n exposed at 600 degreesC indicated the possibility of a lithium aluminate compound formation. Bulk, polycrystalline specimens of CaO (99.9% purity) s howed mass losses above 500 degreesC indicating a possible dissolution prob lem that had not been observed in previous short-term screening tests and i s not predicted based on thermodynamic calculations. Doping of the lithium with oxygen tin the case of CaO) did not appear effective in reducing the m ass loss at 600 degreesC. (C) 2001 Published by Elsevier Science B.V.