Measurement of nanoscale local stress distribution in phase-separated glass using scanning transmission electron microscopy-cathodoluminescence

Phase-separated glass (PSG) is being used widely for manufacturing scientific apparatus and kitchenware, owing to its advantages of high hardness and heat resistance, which can be attributed to its sea- and island-like structures on the nanoscale. There is a growing demand in the glass industry for methods for evaluating and visualizing the local stress distribution in such glass materials at the nanoscale in order to elucidate their fracture mechanism and to obtain more information to develop even harder glass materials. In this study, we clarified the correlation between the local stress in this type of glass material and its associated nanoscale structure using a nanoelectron probe based on scanning transmission electron microscopy and cathodoluminescence. The peak shift of an emission line corresponding to an intentionally doped rare-earth element was measured based on the piezospectroscopic effect. We found that the sea- and island-like structures, whose origins can be attributed to the difference in the thermal expansion coefficients of the two phases, mutually push each other. This result was confirmed by a simple finite-element method simulation. The present result suggests that the local mechanical properties of PSG can be well described by a coherent elastic continuum consisting of the phases that evolve during thermal treatment.