Details
Original language | English |
---|---|
Pages (from-to) | 49-61 |
Number of pages | 13 |
Journal | Physics and Chemistry of Glasses: European Journal of Glass Science and Technology Part B |
Volume | 60 |
Issue number | 2 |
Publication status | Published - 1 Apr 2019 |
Abstract
Dissolved water has major impact on the physical and chemical properties of phosphate glasses. In the present study we have investigated the structural response to water incorporation for glasses in the system Li2O-MgO-Al2O3-P2O5. Glasses containing 0-8 wt% H2O were synthesised at 500 MPa confining pressure in internally heated gas pressure vessels at 1323 K (LMP, Al-poor glass) and 1423 K (LMAP, Al-enriched glass). Water contents of glasses were determined by pyrolysis and subsequent Karl-Fischer titration (KFT) and/or by infrared spectroscopy. Density varies nonlinearly with water content implying large structural changes when adding up to 2 wt% H2O to the dry glass. Glass transition temperatures measured by differential thermal analysis (DTA) continuously decrease with water content. The trend can be explained by depolymerisation of the phosphate network. Near-infrared spectroscopy shows that even in Al poor glasses only a minority of dissolved water is present as H2O molecules, but the largest amount is present as OH groups formed by hydrolysis of P-O-P bonds. The network is stabilised by aluminium which is predominantly six-coordinated in these glasses as shown by27Al MAS NMR spectroscopy. With increase of Al in the glasses, breaking up of the phosphate network through hydrolysis is depressed, i.e. much lower OH contents are formed at same total water content. Network depolymerisation upon addition of H2O is evident also from31P MAS NMR spectroscopy. While phosphate tetraheda are crosslinked by two to three bridging oxygen in dry glasses, diphosphate groups are dominant in glasses containing 8 wt% H2O.
ASJC Scopus subject areas
- Materials Science(all)
- Electronic, Optical and Magnetic Materials
- Physics and Astronomy(all)
- Condensed Matter Physics
- Chemistry(all)
- Physical and Theoretical Chemistry
- Materials Science(all)
- Materials Chemistry
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In: Physics and Chemistry of Glasses: European Journal of Glass Science and Technology Part B, Vol. 60, No. 2, 01.04.2019, p. 49-61.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Structural investigation of hydrous phosphate glasses
AU - Balzer, Robert
AU - Behrens, Harald
AU - Reinsch, Stefan
AU - Fechtelkord, Michael
N1 - Funding Information: This research was supported by the German Science Foundation (DFG) within the priority program SPP1594. The author thanks two anonymous reviewers for their constructive comments, which helped to improve to the quality of this paper.
PY - 2019/4/1
Y1 - 2019/4/1
N2 - Dissolved water has major impact on the physical and chemical properties of phosphate glasses. In the present study we have investigated the structural response to water incorporation for glasses in the system Li2O-MgO-Al2O3-P2O5. Glasses containing 0-8 wt% H2O were synthesised at 500 MPa confining pressure in internally heated gas pressure vessels at 1323 K (LMP, Al-poor glass) and 1423 K (LMAP, Al-enriched glass). Water contents of glasses were determined by pyrolysis and subsequent Karl-Fischer titration (KFT) and/or by infrared spectroscopy. Density varies nonlinearly with water content implying large structural changes when adding up to 2 wt% H2O to the dry glass. Glass transition temperatures measured by differential thermal analysis (DTA) continuously decrease with water content. The trend can be explained by depolymerisation of the phosphate network. Near-infrared spectroscopy shows that even in Al poor glasses only a minority of dissolved water is present as H2O molecules, but the largest amount is present as OH groups formed by hydrolysis of P-O-P bonds. The network is stabilised by aluminium which is predominantly six-coordinated in these glasses as shown by27Al MAS NMR spectroscopy. With increase of Al in the glasses, breaking up of the phosphate network through hydrolysis is depressed, i.e. much lower OH contents are formed at same total water content. Network depolymerisation upon addition of H2O is evident also from31P MAS NMR spectroscopy. While phosphate tetraheda are crosslinked by two to three bridging oxygen in dry glasses, diphosphate groups are dominant in glasses containing 8 wt% H2O.
AB - Dissolved water has major impact on the physical and chemical properties of phosphate glasses. In the present study we have investigated the structural response to water incorporation for glasses in the system Li2O-MgO-Al2O3-P2O5. Glasses containing 0-8 wt% H2O were synthesised at 500 MPa confining pressure in internally heated gas pressure vessels at 1323 K (LMP, Al-poor glass) and 1423 K (LMAP, Al-enriched glass). Water contents of glasses were determined by pyrolysis and subsequent Karl-Fischer titration (KFT) and/or by infrared spectroscopy. Density varies nonlinearly with water content implying large structural changes when adding up to 2 wt% H2O to the dry glass. Glass transition temperatures measured by differential thermal analysis (DTA) continuously decrease with water content. The trend can be explained by depolymerisation of the phosphate network. Near-infrared spectroscopy shows that even in Al poor glasses only a minority of dissolved water is present as H2O molecules, but the largest amount is present as OH groups formed by hydrolysis of P-O-P bonds. The network is stabilised by aluminium which is predominantly six-coordinated in these glasses as shown by27Al MAS NMR spectroscopy. With increase of Al in the glasses, breaking up of the phosphate network through hydrolysis is depressed, i.e. much lower OH contents are formed at same total water content. Network depolymerisation upon addition of H2O is evident also from31P MAS NMR spectroscopy. While phosphate tetraheda are crosslinked by two to three bridging oxygen in dry glasses, diphosphate groups are dominant in glasses containing 8 wt% H2O.
UR - http://www.scopus.com/inward/record.url?scp=85066089277&partnerID=8YFLogxK
U2 - 10.13036/17533562.60.2.041
DO - 10.13036/17533562.60.2.041
M3 - Article
AN - SCOPUS:85066089277
VL - 60
SP - 49
EP - 61
JO - Physics and Chemistry of Glasses: European Journal of Glass Science and Technology Part B
JF - Physics and Chemistry of Glasses: European Journal of Glass Science and Technology Part B
SN - 1753-3562
IS - 2
ER -