Structure of vitreous P 2O 5 and alkali phosphate glasses

Abstract

The structure of vitreous P 2O 5 (v-P 2O 5), sodium ultraphosphate glasses, (Na 2O) x (P 2O 5) 100− x ( x=10, 20), and alkali metaphosphate glasses, MePO 3 (Me=Li, Na, K, Rb and Cs), have been studied by neutron diffraction. Structural features in the neutron structure factors, S( Q), characteristic of intermediate-range ( Q ≲ 3 Å −1) order were identified. The feature of intermediate-range order in v-P 2O 5 is accounted for by the P 4O 10 molecule packing model. The addition of the alkali metal modifier, Na, has an effect on the intermediate-range structure due to destruction of the PO 4 network structure. Around x ∼ 50 a new peak appears at lower Q than the intermediate-range order peak, which is found in the S( Q)'s of all alkali metaphosphate glasses, which may be associated with extended-range order. The length scale of the extended-range order increases with Me + size. These phenomena can be explained by the affects of oxygen atoms, i.e. PO 4 chain-like units, ordering around the Me +.