Crystallization behavior of bismuth oxide nano-glass studied via in situ transmission electron microscopy

The substitution of bismuth oxide for lead in glass and decreasing the particle size of glass powders to the nanoscale have both attracted considerable interest as techniques for decreasing the maximum firing temperature and alleviating environmental problems. However, crystallization during firing is an issue that needs to be solved. In this study, we investigated the sintering behavior of nanosized bismuth oxide glass and the mechanism of its crystallization. The crystallization behavior during sintering was analyzed by hot-stage microscopy. The microscopic sintering interaction between individual nanoglass particles was observed by in situ transmission electron microscopy. The glass softening and densification starting temperatures were dramatically decreased when decreasing the particle size from micro to nanoscale. Based on this study, the bloating of nanostructured bismuth oxide glass starts at 370 °C. This corresponds with the dissociation temperature of bismuth oxide. Therefore, the bloating phenomenon during the sintering of the nanoglass powder is attributed to the thermal dissociation of bismuth oxide.