Cavity formation at cleavage cracks in KBr:Sn

When crystals of KBr are heated in an atmosphere of SnBr2 and nitrogen, lines of cavities are found near cleavage cracks. The cavities are formed at cleavage steps in regions of the cleavage cracks which have closed up before or during the heat treatment. In some cases, enhanced lumiriescencc emission is associated with the lines of cavities.