The structure of alkali silicate glasses and melts: A multi-spectroscopic approach by Cedrick A. O'Shaughnessy A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy in Geology Graduate Department of Earth Sciences University of Toronto c Copyright 2019 by Cedrick A. O'Shaughnessy Abstract The structure of alkali silicate glasses and melts: A multi-spectroscopic approach Cedrick A. O'Shaughnessy Doctor of Philosophy in Geology Graduate Department of Earth Sciences University of Toronto 2019 The structure of alkali silicate glasses and melts is investigated using a multi-spectroscopic approach. Raman spectroscopy is used to characterize the local to intermediate range order within the glasses. We show that the distribution of rings varies as a function of composition, with 3-membered rings gaining importance with increasing alkali content. We apply a newly developed model for the fitting of the high n frequency envelope related to SiO4 symmetric stretch vibrations of Q species. These fits are interpreted using the idea of modifier bound bridging oxygen. The proportions of the different Qn species vary with alkali concentration with Q4 species breaking down to form lower order Qn species with increasing alkali 2 content. The Q peak appears at increasingly higher concentrations of M2O with increasing cation size. This leads us to believe that cations with a higher charge density cluster more readily than cations with a lower charge density. At the ∼20 mol. % composition we see a change in the silicate network, as shown by the absence of a Q4 peak and the proportion of 3-membered rings. The unique behaviour of lithium was investigated using X-ray absorption near-edge structure spec- troscopy. We conducted experiments on a variety of lithium-bearing salts, minerals and glasses (LS: lithium silicate and LMS: lithium alkaline-earth silicate glasses) in order to characterize the lithium bonding environment. The Li K -edge position depends on the electronegativity of the element to which it is bound. The intensity of the first peak varies, depending on the existence of a 2p electron and can be used to evaluate the degree of ionicity of the bond. Crystalline lithium metasilicate has a sharp, strong intensity absorption edge whereas the lithium silicate glasses all have a weak intensity edge feature, similar to that of lithium carbonate. The area of the absorption edge peak increases with the lithium content of the LS glasses. The LMS glasses edge peak changes drastically depending on the alkaline- earth present. The peak area of the LMS glasses decreases with increasing charge density from barium to magnesium. We believe that the presence of Mg leads to more covalent-like Li−O bonds. ii To my loving wife and best friend, Joanna. iii Acknowledgements This thesis would not have been possible without the generosity of the researchers and laboratory facilities where I carried out this research. Daniel Neuville from the Geomaterials laboratory of the Institut de Physique du Globe de Paris who hosted me for months during the summer time. Wayne Nesbitt and Michael Bancroft from the University of Western Ontario were so helpful and generous of their time in which we had great discussions. Lucia Zuin and Tom Reiger were fantastic help on all our visits to the Canadian Light Source. My fellow graduate students, Ben, Heidi, Alex, Simon, and many others I thank you for all the help and friendship. From the office to the GSU, it really was a great time! A huge thank you to my family, Mom & Dad, you've always been there to guide me and more importantly, believe in me. Jola i Mariusz, dziekuje bardzo! Joanna, countless times you have been there to help me get through this. I cannot express how grateful I am to you for your never ending support. I love you so very much! We did it! Finally, to Grant Henderson, who gave me all of these opportunities, and pushed me to keep plugging away. From your gentle encouragements to your more forceful ones, I truly appreciate all the help and advice you've given me. Thanks a lot Mr. Sunshine! Sincerely, thank you all. iv Contents 1 Introduction 1 1.1 Structural models of silicate glasses...............................1 1.1.1 Continuous Random Network (CRN) model......................2 1.1.2 Modified Random Network (MRN) Model.......................3 1.1.3 Central-force network models..............................3 1.1.4 Phase separation.....................................4 1.2 Raman spectroscopy.......................................5 1.2.1 The Raman spectra of silicate glasses.........................5 1.3 X-ray absorption spectroscopy..................................8 1.3.1 XANES of silicate glasses................................9 1.4 Contribution of this thesis.................................... 10 2 Structure-property relations of caesium silicate glasses from room temperature to 1400 K: implications from density and Raman spectroscopy 11 2.1 Introduction............................................ 12 2.2 Methods.............................................. 14 2.2.1 Glass synthesis...................................... 14 2.2.2 Raman spectroscopy................................... 15 2.3 Results............................................... 16 2.3.1 Room temperature Raman spectroscopy........................ 16 2.3.2 High-temperature Raman spectroscopy........................ 18 2.4 Discussion............................................. 19 2.4.1 The Boson peak..................................... 19 2.4.2 The D1 and D2 bands: 495 and 606 cm−1 ....................... 20 2.4.3 The C peak (770 cm−1)................................. 22 2.4.4 The high frequency region (850-1250 cm−1)...................... 24 2.4.5 Insights from high-temperature Raman spectra.................... 29 2.5 Conclusions............................................ 32 3 The structure of high-silica alkali silicate glasses: Revisited 34 3.1 Introduction............................................ 35 3.2 Methods.............................................. 41 3.2.1 Glass synthesis...................................... 42 3.2.2 Raman spectroscopy................................... 42 v Experimental measurements............................... 42 The fitting of Raman spectra.............................. 42 3.3 Results............................................... 44 3.3.1 Density and molar volume of alkali silicate glasses.................. 44 3.3.2 Raman spectra of alkali silicate glasses......................... 45 The behaviour of the D1 and D2 bands (495 and 600 cm−1)............. 45 The symmetric stretch region (Qn species: 850-1300 cm−1)............. 45 3.4 Discussion............................................. 52 3.4.1 The D1 and D2 bands (495 and 600 cm−1)...................... 52 The relative intensity of the D1-D2 bands in alkali silicate glasses.......... 52 The splitting of the D1-D2 bands in alkali silicate glasses.............. 54 Implications from Percolation theory.......................... 54 3.4.2 The high frequency peak (800-1300 cm−1)....................... 61 The polarizability of Q4 species............................. 61 The asymmetry of the Q3 band............................. 61 The appearance and increase of Q2 species: implications for the silicate glass network 62 3.5 Conclusions............................................ 63 3.5.1 Defect bands and their behaviour............................ 63 3.5.2 Q4 band properties.................................... 63 3.5.3 The Q3 band asymmetry: M−BO interactions & Qn;ijkl clustering......... 63 3.5.4 Q2 species and the clustering of alkalis in silicate glasses............... 63 3.5.5 Implications for the structural model of alkali silicate glasses............ 64 3.6 Acknowledgments......................................... 64 4 A Li K -edge XANES study of salts and minerals 76 4.1 Introduction............................................ 77 4.2 Methods.............................................. 78 4.2.1 Mineral samples..................................... 78 4.2.2 X-ray Absorption Near-Edge Structure (XANES) Spectroscopy........... 78 4.3 Results............................................... 80 4.3.1 Lithium salts and metasilicate............................. 81 Lithium chloride (LiCl)................................. 81 Lithium sulphate (Li2SO4)............................... 81 Lithium metasilicate (Li2SiO3)............................. 82 Lithium carbonate (Li2CO3).............................. 82 4.3.2 Lithium aluminosilicates minerals (LAS)........................ 83 Eucryptite (LiAlSiO4).................................. 83 Spodumene (LiAlSi2O6)................................. 83 Petalite (LiAlSi4O10)................................... 85 4.3.3 Lithium phosphates (PO4)............................... 85 Montebrasite (LiAl(PO4)(OH))............................. 85 2+ Lithiophilite (LiMn PO4)............................... 85 4.3.4 Complex lithium-bearing silicates: phyllosilicates and cyclosilicates......... 86 Elbaite (Na(Li;Al)3Al6(Si6O18)(BO3)(OH)3(OH)).................. 87 vi Lepidolite (KLi2Al · (Si4O10)(F;OH)2)......................... 88 2+ Zinnwaldite (KLiFe Al(AlSi3O10)(F;OH)2)...................... 88 2+ 2+ Neptunite (LiNa2K(Fe ;Mn )2Ti2(Si8O24))..................... 88 4.4 Discussion............................................. 89 4.4.1 Lithium salts and metasilicate............................. 89 4.4.2 Bond length distortion in lithium aluminosilicate minerals.............. 90 4.4.3 Complex silicates....................................