Phase-separation of lead borate glasses under different gravity conditions

Glasses with the composition 3.5PbO · 96.5B₂O₃ were melted and solidified through drop shaft experiment and ground experiment to explore the phase-separation of the glass under abnormal gravity condition. The composition homogeneity and the microstructure for different samples were compared. Results show that all the samples phase-separated into two different glass phases, the separated Pb-rich phase and the continuous B-rich phase, regardless of the gravity level in which the phase-separation happened. For the sample from experiment PB-1, the size of separated Pb-rich phase in the top is much smaller than that in the bottom. The big heterogeneity in composition along the vertical direction and obvious differences in microstructures for this sample could be attributed to the high gravity condition that the phase-separation occurred. There is no visible composition heterogeneity and the microstructure difference for the samples from experiments PB-2 and PB-G.