Etching Studies of Beryllium Oxide Crystals

Chemical etching behaviour of BeO crystals was investigated for selected etchants ranging from basic to acidic in nature. Surface-emergent defects (dislocations, enclosed platinum crystals, point-defect concentrations, surface mechanical damage, twin boundaries) give rise to recognisable etch figures that are characteristic of etchant, defect type, and orientation of emergence face. Gross etching rates (in the absence of surface-emergent defects) are strongly anisotropic for both basic and acidic etchants, reflecting the crystallographic polarity of the BeO crystal structure; intermediate etchants give nearly isotropic etching. The details of gross and figure etching are described.