The role of double poison in the etching of potassium chloride crystals

Abstract

The authors give an experimental account of how additions of calcium chloride to the etchant, consisting of cadmium chloride and methanol, modifies the etch pits formed on the freshly cleaved surfaces of potassium chloride crystals. As the concentration of calcium chloride is increased in the etchant, the etched samples show the following essential features. A progressive increase in the degree of surface roughness. A gradual increase in the shallowness of etch pits. A systematic variation in the morphology of the etch pits and finally the orientation changes from the (100) directions to the (110) directions. Also, the effect of decreasing the cadmium chloride concentration in the etchant is observed. These observations suggest that calcium chloride inhibits the action of the poison, i.e. cadmium chloride, during etching.