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Structure of Rare-Earth Aluminosilicate Glasses Probed by Solid-State NMR Spectroscopy and Quantum Chemical Calculations
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).ORCID-id: 0000-0002-7156-559X
2016 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Aluminosilicate glasses incorporating rare earth elements feature highly beneficial physical and chemical properties, at the level beyond that accessible for compositions based on alkali and/or alkaline earth metals. Extraordinary hardness, high glass transition temperatures and indices of refraction, favorable coefficients of thermal expansion, as well as excellent chemical durability, result in many potential technological applications. However, in contrast to the systematically explored and commercially exploited aluminosilicate glasses that contain Na, K, and Ca elements, their rare earth counterparts were sparsely investigated, although exhibit several unique structural features.

This thesis explored the short- and medium-range structural organization of glasses belonging to the ternary RE2O3—Al2O3—SiO2 systems, where RE denotes one of the trivalent and diamagnetic rare earth metal ions of scandium (Sc), yttrium (Y), lanthanum (La), and lutetium (Lu). Comprehensive multinuclear solid-state nuclear magnetic resonance studies complemented with atomistic molecular dynamics computer simulations and quantum chemical calculations provided detailed insight into local environments of the glass networkforming elements (Si, Al), oxygen species, as well as the rare earth ions, thereby offering a deeper understanding of the glass structure.

sted, utgiver, år, opplag, sider
Stockholm: Department of Materials and Environmental Chemistry (MMK), Stockholm University , 2016.
HSV kategori
Forskningsprogram
fysikalisk kemi
Identifikatorer
URN: urn:nbn:se:su:diva-129112ISBN: 978-91-7649-398-4 (tryckt)OAI: oai:DiVA.org:su-129112DiVA, id: diva2:919657
Disputas
2016-06-07, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 14:00 (engelsk)
Opponent
Veileder
Merknad

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

Tilgjengelig fra: 2016-05-13 Laget: 2016-04-14 Sist oppdatert: 2019-12-12bibliografisk kontrollert
Delarbeid
1. Local structures and al/si ordering in lanthanum aluminosilicate glasses explored by advanced al 27 nmr experiments and molecular dynamics simulations
Åpne denne publikasjonen i ny fane eller vindu >>Local structures and al/si ordering in lanthanum aluminosilicate glasses explored by advanced al 27 nmr experiments and molecular dynamics simulations
Vise andre…
2012 (engelsk)Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 14, nr 45, s. 15866-15878Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The structures of 15 La-Al-Si-O glasses, whose compositions span 11-28 mol% La2O3, 11-30 mol% Al2O3, and 45-78 mol% SiO2, are explored over both short and intermediate length-scales by using a combination of solid-state Al-27 magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics (MD) simulations. MAS NMR reveals Al speciations dominated by AlO4 groups, with minor but significant fractions of AlO5 (5-10%) and AlO6 (less than or similar to 3%) polyhedra present in all La2O3-Al2O3-SiO2 glasses; the amounts of Al-[5] and Al-[6] coordinations increase for decreasing molar fraction of Si. The MD simulations reproduce this compositional trend, with the fractional populations of AlOp groups (p = 4, 5, 6) according well with the experimental results. The modeled La speciations mainly involve LaO6 and LaO7 polyhedra, giving a range of average La3+ coordination numbers between 6.0 and 6.6; the latter increases slightly for decreasing Si content of the sample. Besides the expected bridging and non-bridging O species, minor contributions of oxygen triclusters (<= 9%) and free O-2(-) ions (<= 4%) are observed in all MD data. The glass structures exhibit a pronounced Al/Si disorder; the MD simulations reveal essentially random SiO4-SiO4, SiO4-AlOp and AlOp-AlOq (p, q = 4, 5, 6) associations, including significant amounts of AlO4-AlO4 contacts, regardless of the n(Al)/n(Si) molar ratio of the glass. The strong violation of Al-[4]-Al-[4] avoidance is verified by 2D Al-27 NMR experimentation that correlates double-quantum and single-quantum coherences, here applied for the first time to aluminosilicate glasses, and evidencing AlOp-AlOq connectivities dominated by AlO4-AlO4 and AlO4-AlO5 pairs. The potential bearings from distinct fictive temperatures of the experimental and modeled glass structures are discussed.

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Identifikatorer
urn:nbn:se:su:diva-83973 (URN)10.1039/c2cp42858j (DOI)000310460400030 ()
Merknad

AuthorCount:5;

Tilgjengelig fra: 2012-12-17 Laget: 2012-12-17 Sist oppdatert: 2019-12-12bibliografisk kontrollert
2. Direct O-17 NMR experimental evidence for Al-NBO bonds in Si-rich and highly polymerized aluminosilicate glasses
Åpne denne publikasjonen i ny fane eller vindu >>Direct O-17 NMR experimental evidence for Al-NBO bonds in Si-rich and highly polymerized aluminosilicate glasses
2015 (engelsk)Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 17, nr 28, s. 18269-18272Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

By using solid-state O-17 NMR spectroscopy, we provide the first direct experimental evidence for bonds between Al and non-bridging oxygen (NBO) ions in aluminosilicate glasses based on rare-earth (RE) elements, where RE = {Lu, Sc, Y}. The presence of similar to 10% Al-NBO moieties out of all NBO species holds regardless of the precise glass composition, at odds with the conventional structural view that Al-NBO bonds are absent in highly polymerized and Si-rich aluminosilicate glass networks.

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urn:nbn:se:su:diva-119772 (URN)10.1039/c5cp02985f (DOI)000357808500005 ()
Tilgjengelig fra: 2015-08-24 Laget: 2015-08-24 Sist oppdatert: 2019-12-12bibliografisk kontrollert
3. The Bearings from Rare-Earth (RE=La, Lu, Sc, Y) Cations on the Oxygen Environments in Aluminosilicate Glasses: A Study by Solid-State 17O NMR, Molecular Dynamics Simulations and DFT Calculations
Åpne denne publikasjonen i ny fane eller vindu >>The Bearings from Rare-Earth (RE=La, Lu, Sc, Y) Cations on the Oxygen Environments in Aluminosilicate Glasses: A Study by Solid-State 17O NMR, Molecular Dynamics Simulations and DFT Calculations
(engelsk)Manuskript (preprint) (Annet vitenskapelig)
HSV kategori
Forskningsprogram
fysikalisk kemi
Identifikatorer
urn:nbn:se:su:diva-129064 (URN)
Tilgjengelig fra: 2016-04-13 Laget: 2016-04-13 Sist oppdatert: 2019-12-12bibliografisk kontrollert
4. Sc and Y Environments in Rare-Earth Aluminosilicate Glasses Unveiled by 45Sc and 89Y NMR Spectroscopy, MD Simulations, and DFT Calculations
Åpne denne publikasjonen i ny fane eller vindu >>Sc and Y Environments in Rare-Earth Aluminosilicate Glasses Unveiled by 45Sc and 89Y NMR Spectroscopy, MD Simulations, and DFT Calculations
(engelsk)Manuskript (preprint) (Annet vitenskapelig)
HSV kategori
Forskningsprogram
fysikalisk kemi
Identifikatorer
urn:nbn:se:su:diva-129065 (URN)
Tilgjengelig fra: 2016-04-13 Laget: 2016-04-13 Sist oppdatert: 2019-12-12bibliografisk kontrollert

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