Abstract:

Glasses with composition 80TeO2 - 5Bi2O3 - 15WO3 (mol %) were studied as host for crystals structure grown under thermal treatments. It was observed that the dispersion of the size of the crystals can be controlled by subjecting the samples to two-step heat treatment – first during 24-hour at 340 ° C near of the glass transition temperature (Tg) and another about 40 ° C above the Tg. With an 80-hour thermal treatment at 40 ° C above the Tg, crystals with approximately 30 µm of size was observed. The treatment at the same temperature but during 24 hours it was observed that the crystals size was about 3 µm. Nanostructures with size about 80 - 100 nm were observed in samples subjected to the same type of heat treatment, but with minor time intervals - 5 hours at 40 °C above the Tg. The crystalline phase - Bi2O3 - was identified by powder X-ray diffraction (XRD), and the crystal size was evaluated using a scanning electron microscope (SEM) and also using atomic force microscopy (AFM). Images of the largest crystals have also been made using optical microscopy. It was also possible to observe that during the pouring of melting glass, there was the pulling of fiber with a diameter of 140 µm. The results of this study indicate that it is possible to grow nanoscale structures, thermally stimulated, into 80TeO2 - 5Bi2O3 - 15WO3 glasses.