Dissolution Kinetics and Etch Pit Morphology of CaF2 Single Crystals

The effect of temperature and concentration of HCl aqeous solutions on the etching behaviour on the face {111} of CaF₂ single crystals is investigated. It has been observed that the shape and the evolution of etch pits and the values of dissolution rate depend on the etching conditions. From the plots of logarithm of dissolution rate versus inverse of absolute temperature the values of activation energy and the pre-exponential factor for the dissolution process are computed. It has been found that the value of the activation energy and of the pre-exponential factor do not remain constant with acid concentration, but exhibit a minimum for the concentration of 6 N.