Effect of crystal orientation on lapping and polishing processes of natural quartz

Lapping and polishing processes of natural quartz are investigated in relation to crystalline orientation and applied normal stress. Weight loss measurements and surface profilometry were carried out in X-, Y-, Z- and AT-cut samples. It is shown that the relationship found between material removal rate and stress depends on specimen orientation. This behavior is discussed in relation to fracture toughness and scratch hardness anisotropy. Scanning electron microscopy (SEM) shows that microcracking is the main mechanism involved with material removal in lapping whereas plastic deformation is observed on surfaces polished with high normal stresses. Surface profiles and SEM micrographs show that roughness of lapped surfaces decreases with increasing the normal stress but an opposite behavior is observed in polished surfaces