Ion-induced amorphization of murataite

Murataite A(4)B(2)C(7)O(22=x), where A = Na+, Ca2+, REE3+, An(3+/4+); B = Mn2+/3+, Zn2+; C = Ti4+, Fe3+, Al3+; 0less than or equal toxless than or equal to1, is an isometric, derivative of the fluorite-structure. Murataite is potentially suitable as a phase for the immobilization of rare earth (REE) and actinide elements (An). Murataite structures with three- (3C), five- (5C), and eight-fold (8C) multiples of the fluorite unit cell parameters have been identified. Radiation-induced amorphization of murataite has been investigated by 1 MeV Kr+ ion irradiation of three ceramic samples produced by melting in a resistive furnace and a cold crucible at 1400-1600 degreesC. The 1 MeV Kr+ ion irradiations were performed at room temperature using IVEM-Tandem Facility at Argonne National Laboratory. Radiation damage was observed by in-situ TEM. Initially, the irradiation caused disordering of the murataite structure. Murataite was rendered fully amorphous at a dose of (1.7similar to1.9) x 10(18) ion/m(2). The pyrochlore structure phase (2C) is more radiation resistant to ion irradiation-induced amorphization than the murataite structure. Combining results on murataite with those pyrochlore and fluorite, a generally increasing trend in the susceptibility to ion beam damage is found in the fluorite-related structures as a function of the increasing multiples of the fluorite unit cells.