Evidence for the Coordination Number Change of Rare Earth Ions in Rare Earth Phosphate Glasses

Rare earth phosphate glasses of the composition Ln(PO3)3·KPO3 (Ln : rare earth ion) were prepared and their glass transition temperatures (Tg′s) were measured. From the Tg variation across the series, it is shown that the coordination number of rare earth ions changes, probably from nine to eight, in the middle of the series.