Photon emission during fracture of engineering ceramics and glasses

Photon emission (phE) often accompanies fracture of ceramics. The author has studied the phE for engineering ceramics and glasses to clarify its emission mechanisms. This paper reviews the recent studies to describe several factors contributing to the phE and to discuss phE mechanisms. Recently, it has been found that the phE is affected by surrounding gas, bending strength and fracture mode. The phE intensity depends on both of kind and pressure of surrounding gas. The dependence demonstrates that discharge of the gas is one of the origins of the phE. The positive correlation between bending strength and the phE intensity is observed for glass and single crystal ceramics, showing that the phE is associated with released energy by fracture. In polycrystalline ceramics, the phE intensity does not depend clearly on bending strength but on the proportion of transgranular fracture. This indicates that grain boundary has a large effect on the phE.