High-resolution electron microscopy of electron irradiation damage in apatite

Electron irradiation-induced damage of apatite was observed in situ during examination by transmission electron microscopy. Radiation damage of this type was identified by hexagonally-shaped patches, sometimes as small as 2 unit cells in diameter, with crystallographic edges indicating a faceted three-dimensional shape. A two-dimensional lattice contrast continued throughout the area of the patch. This type of damaging process was interpreted in terms of a radiation-induced voidage model resulting from anion displacement in the apatite crystal structure. After reasonably long periods (>20 mins) of intense electron beam irradiation, local amorphization and collapse of the apatite crystal structure occurred.