Dislocations in ammonium perchlorate

Abstract

The formation of etch pits on the cleavage surfaces of ammonium perchlorate single crystals has been studied by optical and electron microscopy. Ethyl and butyl alcohols and their mixtures were the most satisfactory etchants. Well defined etch pits could not be detected on the c face which dissolves very rapidly, going through three separate stages: numerous round etch pits appear, followed by elongated roughly parallel curved channels, which finally become connected, leaving nearly circular flat-topped ‘hills’ with clearly delineated terraced sides. However, when the crystals are etched in butyl alcohol, well defined rectangular pits are formed on the m face having either a 3:1 or 4:1 length-to-width ratio; they resemble elongated stepped or terraced pyramids, and are always orientated with their long sides parallel to the [001] direction.

Some of the etch pits on the cleavage surfaces were found to be distributed randomly while others are clearly aligned in specific crystal directions. Strained crystals exhibit slip bands and the various possible systems were deduced by computing, from the crystal structure, the most likely low-index slip planes and slip directions which are consistent with the observed etch pit alignments and slip bands.