LITHIUM SOL-GEL CERAMICS FOR TRITIUM BREEDING APPLICATION

Tritium release experiments are performed on different lithium sol-gel ceramics showing identical microstructures. For gamma-LiAlO2 type ceramics [Li4+xAl4-3xSi2xO8 (0 less than or equal to x less than or equal to 0.25)], the increase of the concentration of silicon atoms leads to a reduction of the temperature at which the tritium release curve reaches a maximum. This corresponds to a decrease of diffusion and desorption activation energies and can be related to the acidity of silanol groups which improves the tritium ion mobility. Compared to gamma-LiAlO2 type ceramics, the tritium release takes place at lower temperatures for lithium zirconate and titanate ceramics. Lithium titanate ceramics present a well resolved release peak, at 300 degrees C, associated with a very low value of the desorption energy. This could be related to the presence of reducing non-stoichiometry defects at the ceramic surface.