Secondary phase-separation of lead borate glass under different gravity conditions

The lead borate glass was melted and solidified under different gravity conditions, and microstructure of the samples was observed through SEM. The secondary phase-separation of the glasses were explored and the possible immisibility region existed in the lead borate system was suggested. Results show that the lead borate glass first phase separated into two glassy phases: lead-rich phase and borate-rich phase, which were both believed to continue the phase-separation (secondary phase-separation). The microstructure of the sample is very different, which is attributed to the pattern of secondary phase-separation. In addition to the known immiscibility region in the PbO-B₂O₃ system, there are at least two potential immiscibility regions existing, although the exact position can not be determined. It was also found that the position of the immiscibility regions is related to the gravity condition under which the secondary phase-separation happened.