Crystallization in lead tungsten fluorophosphate glasses

Abstract

The glass forming ability was investigated in the codoped Er 3+ /Yb 3+ ternary system NaPO 3 -WO 3 -PbF 2 with increasing amounts of PbF 2. It has been found that glass samples can be obtained for PbF 2 contents ranging from 0 mole% to 50 mole% for the codoped samples and an undoped sample containing 60% of lead fluoride could also be vitrified. Thermal properties of the most PbF 2 concentrated glasses exhibit strong dependence of the composition with a decrease of the glass transition temperatures and thermal stabilities against devitrification with increasing the lead fluoride content. These glass samples were heat-treated near the crystallization peaks and the X-ray diffraction measurements pointed out that the dominant phase which precipitates from the glass samples containing 40% and 50% of PbF 2 is the lead fluorophosphate phase Pb 5 F(PO 4) 3 whereas the sample containing 60% of PbF 2 exhibits a preferential bulk crystallization of cubic lead fluoride β-PbF 2.