Colloid formation and laser-induced bleaching in fluorite

Colloid formation and subsequent laser-induced bleaching in fluorite has been studied by transmission electron microscopy and electron diffraction. At high incident electron-beam (e-beam) energies, Ca colloids with diameter similar to10 nm form a simple cubic superlattice with lattice parameter asimilar to18 nm. The colloids themselves are topotactic with the fluorite matrix forming low-energy interfaces close to a Sigma=21 special grain boundary in cubic materials. Laser irradiation using lambda=532 nm has been shown to effectively bleach the e-beam-irradiated samples returning the fluorite to its monocrystalline state. The bleached samples appear more resistant to further colloid formation. (C) 2004 American Institute of Physics.