Chawon Hwang

Effects of heat treatment on morphology and crystallization of glass and film containing a large amount of CdO

AbstractThe authors report the effects of heat treatment on the morphological and crystallization behaviors of photoresponsive 65CdO-17.5B2O3-17.5SiO2 (mol. %) bulk glass and its film. The bulk glass exhibited clear phaseseparation morphology when heat treated at 575°C for 1 h, and started to crystallize preferentially into phases with high CdO contents after heat treatment at 595°C. Heat treatment of the films at 575°C for 2 h resulted in simultaneous phase separation and crystallization. The morphology of the film heat treated at 575°C was found to comprise discontinuous CdO-poor phases formed in the matrix of a CdO-rich phase; however, these discontinuous phases became interconnected upon subsequent heat treatment at temperatures over 575°C. Various phases were formed concurrently by crystallization, with relatively large crystals of high CdO content preferentially forming in the CdO-rich phase, whereas small crystals of low CdO content formed in the CdO-poor phase. It was found that the main crystals of the heat-treated films transformed into crystal phases with higher CdO contents with increasing heat-treatment temperature, and this is likely caused by the change in composition related to phase separation.