Cation Effects on Anion Distributions in Aluminophosphate Glasses

Alkali aluminophosphate glasses, including those in the system x Al 2 O 3 ·(1− x )CsPO 3 (0 ≤ x ≤ 0.25), were examined by high‐performance liquid chromatography (HPLC), infrared (IR), and 27 Al magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopies. Phosphate anions become progressively shorter with the addition of alumina to a metaphosphate glass. Al 3+ ions are initially incorporated into the structure in octahedral sites, but the average Al coordination number (CN) decreases with increasing alumina content and tetrahedral species are the preferred moiety when [O]/[P] > 3.5. Al[4] sites appear to be associated with monophosphate (Q 0 ) anions. The role of modifier size on aluminophosphate structure is investigated. At low alumina content (<15 mol%), the disproportionation of pyrophosphate anions into triphosphate and orthophosphate anions is responsible for the lower average Al CN of cesium aluminophosphate glasses compared with sodium aluminophosphate glasses.