| Abstract: | An investigation of the etching behaviour of cleaved octahedral faces of calcium fluoride crystals in sulphuric acid of different concentrations and at various temperatures is carried out. It is observed that the morphology of dislocation etch pits depends on the temperature and concentration of the acid. With an increase in the acid concentration, growth of whiskers, elongated platelets, hexagonal and dice-shaped elevations, spherulites and sheaves is observed. Temperature of the etchant also has an effect on their formation. By X-ray diffraction techniques, the compounds forming the whiskers and elongated platelets, and hexagonal and dice-shaped features are identified as CaSO4 · 2 H2O and CaSO4, respectively. The mechanism of the growth of CaSO4 · 2 H2O and CaSO4 and the change in the morphology of selective etch pit are discussed. |
