Structural Relaxation in Polyanionic Sodium Fluorophosphate Glasses
Structural heterogeneity is a common feature of all glasses, however, little is known about the underlying contributions of chemical fluctuations and modulations in free volume in concrete glass forming systems. In this investigation, we relate the dynamics of structural relaxation of (100-x)NaPO3-x...
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Frontiers Media S.A.
2019-07-01
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| Series: | Frontiers in Materials |
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| Online Access: | https://www.frontiersin.org/article/10.3389/fmats.2019.00165/full |
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| author | Courtney Calahoo Jelena Petrovic Quyen Huyen Le Ulrike Werner-Zwanziger Josef Zwanziger Lothar Wondraczek |
| author_facet | Courtney Calahoo Jelena Petrovic Quyen Huyen Le Ulrike Werner-Zwanziger Josef Zwanziger Lothar Wondraczek |
| author_sort | Courtney Calahoo |
| collection | DOAJ |
| description | Structural heterogeneity is a common feature of all glasses, however, little is known about the underlying contributions of chemical fluctuations and modulations in free volume in concrete glass forming systems. In this investigation, we relate the dynamics of structural relaxation of (100-x)NaPO3-xAlF3 glasses to their heterogeneous structure as determined from multinuclear magnetic resonance spectroscopic analysis. For this, we evaluate differential scanning calorimetry (DSC) data using the integral isoconversional method to determine the variation in activation energy, Ea, of the glass transition as a function of temperature and conversion progress. Specific heat measurements from DSC allow for the determination of the effective size of the cooperatively rearranging region (CRR). From 31P, 19F, and 27Al NMR, we observe that the introduction of AlF3 into the NaPO3 network increases the average connectivity (i.e., the number of heteronuclear Al—O—P bonds), rationalizing the higher Ea determined from the DSC measurements. We find highly constrained regions of Al(OP)4F2 with Al—F—Al cross-linking (high Ea) and, simultaneously, more flexible regions of phosphate chains containing P—F··(Na+)n bonds (low Ea); this results in a topologically and dynamically heterogeneous structure as evidenced by the increased variability in Ea with higher AlF3 content. The decreasing size of the CRR reflects the increased heterogeneity: at low AlF3 the CRR is large, while at high AlF3 (high heterogeneity), the CRR is significantly smaller (by a factor of 103). Finally, we relate the heterogeneity to other macroscopic properties, such as Tg and mechanical properties. |
| first_indexed | 2024-12-22T05:18:14Z |
| format | Article |
| id | doaj.art-08d4f82aa7ba44ea94c27a7b956da28d |
| institution | Directory Open Access Journal |
| issn | 2296-8016 |
| language | English |
| last_indexed | 2024-12-22T05:18:14Z |
| publishDate | 2019-07-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Materials |
| spelling | doaj.art-08d4f82aa7ba44ea94c27a7b956da28d2022-12-21T18:37:48ZengFrontiers Media S.A.Frontiers in Materials2296-80162019-07-01610.3389/fmats.2019.00165460904Structural Relaxation in Polyanionic Sodium Fluorophosphate GlassesCourtney Calahoo0Jelena Petrovic1Quyen Huyen Le2Ulrike Werner-Zwanziger3Josef Zwanziger4Lothar Wondraczek5Otto Schott Institute of Materials Research, University of Jena, Jena, GermanyOtto Schott Institute of Materials Research, University of Jena, Jena, GermanyOtto Schott Institute of Materials Research, University of Jena, Jena, GermanyDepartment of Chemistry, Dalhousie University, Halifax, NS, CanadaDepartment of Chemistry, Dalhousie University, Halifax, NS, CanadaOtto Schott Institute of Materials Research, University of Jena, Jena, GermanyStructural heterogeneity is a common feature of all glasses, however, little is known about the underlying contributions of chemical fluctuations and modulations in free volume in concrete glass forming systems. In this investigation, we relate the dynamics of structural relaxation of (100-x)NaPO3-xAlF3 glasses to their heterogeneous structure as determined from multinuclear magnetic resonance spectroscopic analysis. For this, we evaluate differential scanning calorimetry (DSC) data using the integral isoconversional method to determine the variation in activation energy, Ea, of the glass transition as a function of temperature and conversion progress. Specific heat measurements from DSC allow for the determination of the effective size of the cooperatively rearranging region (CRR). From 31P, 19F, and 27Al NMR, we observe that the introduction of AlF3 into the NaPO3 network increases the average connectivity (i.e., the number of heteronuclear Al—O—P bonds), rationalizing the higher Ea determined from the DSC measurements. We find highly constrained regions of Al(OP)4F2 with Al—F—Al cross-linking (high Ea) and, simultaneously, more flexible regions of phosphate chains containing P—F··(Na+)n bonds (low Ea); this results in a topologically and dynamically heterogeneous structure as evidenced by the increased variability in Ea with higher AlF3 content. The decreasing size of the CRR reflects the increased heterogeneity: at low AlF3 the CRR is large, while at high AlF3 (high heterogeneity), the CRR is significantly smaller (by a factor of 103). Finally, we relate the heterogeneity to other macroscopic properties, such as Tg and mechanical properties.https://www.frontiersin.org/article/10.3389/fmats.2019.00165/fullstructural relaxationfluorophosphate glassionic glassstructural heterogeneitythermal analysisstructure-property relationship |
| spellingShingle | Courtney Calahoo Jelena Petrovic Quyen Huyen Le Ulrike Werner-Zwanziger Josef Zwanziger Lothar Wondraczek Structural Relaxation in Polyanionic Sodium Fluorophosphate Glasses Frontiers in Materials structural relaxation fluorophosphate glass ionic glass structural heterogeneity thermal analysis structure-property relationship |
| title | Structural Relaxation in Polyanionic Sodium Fluorophosphate Glasses |
| title_full | Structural Relaxation in Polyanionic Sodium Fluorophosphate Glasses |
| title_fullStr | Structural Relaxation in Polyanionic Sodium Fluorophosphate Glasses |
| title_full_unstemmed | Structural Relaxation in Polyanionic Sodium Fluorophosphate Glasses |
| title_short | Structural Relaxation in Polyanionic Sodium Fluorophosphate Glasses |
| title_sort | structural relaxation in polyanionic sodium fluorophosphate glasses |
| topic | structural relaxation fluorophosphate glass ionic glass structural heterogeneity thermal analysis structure-property relationship |
| url | https://www.frontiersin.org/article/10.3389/fmats.2019.00165/full |
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