• journal_title：American Mineralogist
• Contributor：Daniel R. Neuville ; Grant S. Henderson ; Laurent Cormier ; Dominique Massiot
• Publisher：Mineralogical Society of America
• Date：2010-
• Format：text/html
• Language：en
• Identifier：10.2138/am.2010.3465
• journal_abbrev：American Mineralogist
• issn：0003-004X
• volume：95
• issue：10
• firstpage：1580
• section：†

Calcium aluminate glasses are important materials where AlO_4/2⁻ is the only network former. Aluminum in crystals or glasses between CaO and Al₂O₃ can have different environments as a function of the CaO/Al₂O₃ ratio. Using X-ray absorption at the Al K- and L-edges, Raman and ²⁷Al NMR spectroscopies, we have determined the structural surroundings of Al in glasses, crystals, and melts in this binary system. Aluminum is in octahedral coordination at high-Al₂O₃ content (>80 mol%) and essentially in fourfold coordination with 4 bridging O atoms (BOs) at Al₂O₃ contents between 30 and 75 mol%. At around 25 mol% Al₂O₃, Al is in tetrahedral coordination with two BOs. The presence of higher-coordinated species at high-Al₂O₃ contents and their absence at low Al₂O₃ imply different viscous flow mechanisms for high- and low-concentration Al₂O₃ networks.