Simultaneous measurements of the electron and photon emission accompanying fracture of single-crystal MgO

Abstract

We investigate the simultaneous emission of electrons and photons during the deformation and fracture of two types of high-purity single-crystal MgO. These crystals exhibit significant differences in optical opacity due to differences in void and precipitate concentrations. Measurements of the emission of visible photons during deformation and prior to failure of the crystals are presented, along with the time dependencies of the photon and electron emission during and after fracture. Correlations with fracture strength and fractographic features are also discussed.

Bending Strength Dependence of Fractoluminescence Intensity in Silica Glass, Single Crystal and Polycrystalline MgO

“…The FL decay does not directly reflect fracture process, that is, crack propagation process, because the specimens were fractured in an order of microsecond much faster than the gate time (1 ms). It is considered that the FL process involves electron transition from excited states to ground states 11,12) and/or diffusion-related processes, for example, the recombination of electrons and holes 13,17) . Therefore, the FL decay time probably depended on the lifetime of the excited electrons and/or the diffusion properties, and moreover the gate time of the measuring system might influence the measured decay curve.…”

“…However, only a few experimental results have been reported on the relation 13,15,16) . The purpose of this study is to clarify the relation in ceramics and glasses.…”

“…Dickinson et al observed strong photoluminescence (PL) from step edges and deformed areas on a cleaved surface of single crystal MgO 18) . It was reported that both of the PL and FL were originated from the same emission centers such as F or F + centers 7,11,13) . Therefore, the positive correlation in the single crystal MgO was attributed to the increase in the step density and deformed area on the fracture surface with increasing the released energy by the fracture.…”

“…The authors have also studied the FL in ceramics and glasses [7][8][9][10] . Although a lot of the FL mechanisms are proposed, for example, relaxation of color centers 7,[11][12][13] , gas discharge 8,14) , thermal radiation 7,14) and so on, the mechanism is not completely elucidated yet. For an application of the FL to prediction of the earthquake or to evaluation of fracture behavior, it is necessary to elucidate the FL mechanism completely and then to establish a quantitative model for the FL.…”

NDE Applications of Radio Wave Emission from Stress and Fracture

“…Usually, such experiments are performed under conditions of high or ultra-high vacuum. This type of particle emission has been extensively studied previously, most notably by Dickinson and his co-workers [2J - [7]. Except for previous studies of fracturing rock, performed in connection with early-warning detection of earthquakes [8], [9], and the work of Dickinson, little has been done to characterize the radio wave emission that attends material fractures.…”