Structure and properties of cerium phosphate and silicophosphate glasses

We report on the fabrication, properties, and structure of cerium pyrophosphate glasses and partially substituted cerium silicophosphates. In those glasses, cerium occurs predominantly as Ce(III). A combination of dynamic nuclear magnetic resonance and electrical impedance spectroscopy is used to overcome the problem of assessing cerium speciation. While optical spectroscopy is unable to quantify the ratio of Ce(III)/Ce(IV) due to spectral overlap, proxy observations of the effect of silica-for-cerium substitution on optical extinction and the shape and width of the UV band gap corroborate vibrational spectroscopic data of the structural roles of cerium and silica. While silica bonding to phosphate units appears to stabilize Ce(IV), it also impedes the polaron transport, leading to higher polaron activation energy and lower electronic conductivity. On the other hand, Ce(III) is stabilized by coordinating to P = O.

Automated summary

We investigate the properties and structure of cerium pyrophosphate glasses and partially substituted cerium silicophosphates. The majority of cerium in these glasses is in the Ce(III) state. A combination of dynamic nuclear magnetic resonance and electrical impedance spectroscopy is utilized to determine the cerium speciation. Optical spectroscopy is limited in quantifying the ratio of Ce(III)/Ce(IV), but the effects of silica-for-cerium substitution on optical extinction and the UV band gap provide supporting evidence from vibrational spectroscopy. The stabilization of Ce(IV) by silica bonding to phosphate units restricts polaron transport, resulting in higher polaron activation energy and lower electronic conductivity. Meanwhile, Ce(III) is stabilized by coordinating to P = O.