Quartz: Anomalous weakness of synthetic crystals

Abstract

The strength of a synthetic quartz crystal drops rapidly at 400°C, and at 600°C is a hundredfold lower than at 300°C. Large plastic deformations can be produced without fracture. The predominant mechanism of deformation is translation gliding. The preferred explanation for this anomalous weakness is that this synthetic quartz contains water which has hydrolyzed the silicon-oxygen bonds. The silanol groups so formed are presumed to be rendered sufficiently mobile by elevating the temperature to 400°C so that they align themselves in dislocation lines and move through the crystal with the dislocation under the small applied shear stress.