Transmission Electron Microscope Study of Secondary Phases in Cr3+:LiCaAlF6Single Crystals

Cr3+‐doped LiCaAlF6single crystals, considered as promising laser materials, contain secondary phases of different sizes and shapes which can be observed as "needles" or "dust" by light microscopy. TEM investigations presented in this paper give evidence for precipitation as the reason for the so‐called microscopic "dust". The elongated shape of the so‐called "needles" seems to be a consequence of the microscopic growth of facets which become visible by the decoration of the facet boundaries with microscopic precipitates.