Transmission electron microscopy in MgO single crystals containing a high concentration of hydrogen

Abstract

Cavities in MgO with high hydrogen concentration were studied by transmission electron microscopy. The size of the cavities analysed ranges between 0.1 μm and 1.1 μm, and their concentration and average size is found to depend on the hydrogen content. The cavities are lenticular, octahedral or cubo-octahedral in shape, and their distribution is very inhomogeneous. Microstructures of deformed samples revealed dislocations anchored in the cavities. In lithium-doped MgO samples, Li₂O precipitates are observed after oxidation-reduction treatments. MgO: Li crystals reduced in graphite exhibit a long-lived green phosphorescence.