Plastic deformation of a glass-ceramic

Abstract

Large plastic deformations have been produced in a glass-ceramic derived from the SiO₂–Li₂O–ZnO system, and the nature of the deformed phases has been studied using the combined techniques of x-ray diffraction, replica and thin foil electron microscopy and electron diffraction. Typical deformation structures have not been observed in the crystalline phases which are α-quartz, lithium disilicate and lithium zinc silicate. Consequently, it is concluded that any crystal deformation required in order to accommodate shear in the glassy phase, must be accompanied by recrystallization. The lithium disilicate grains contain plates, ∼ 100 Å thick, of ‘foreign’ material which is attributed to lithium zinc silicate. The variation of plastic deformation with temperature is discussed in terms of the present observations.