Some aspects of photon emission of polycrystalline ceramics during fracture

Abstract The photon emission during fracture was investigated on MgO, A12O3, Si3N4 and ZrO2 ceramics, soda-lime glass and an A12O3 single crystal. The single-edge notched beam test was carried out, and the emitted photons were detected by a photomultiplier tube in the pulse-counting regime. At fracture, the photon emission increased rapidly and then decayed with a characteristic time. The peak count strongly depended on material. The grain size also had a great influence on the emission, because the emission was controlled by the crack extension path. In the case of the alumina single crystal, the photon emission showed distinct crystal orientation dependence. The wavelength distribution of the photons was measured for the MgO using different photomultiplier tubes and optical filters. This indicated that ultraviolet or purple light was emitted at fracture and subsequently red or infrared light continued for several hundreds of milliseconds. Based on the results, the photon emission mechanism was discussed.