Date of Award
January 2016
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Physics & Astrophysics
First Advisor
Kanishka Marasinghe
Abstract
In the first part of this work, the atomic-scale structure around rare-earth (RE = Pr, Nd, Eu, Dy, and Er) cations (RE3+) in rare-earth sodium ultraphosphate (REUP) glasses were investigated using RE LIII-edge (RE = Nd, Er, Dy, and Eu) and K-edge (RE = Pr and Dy) Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. (RE2O3)x(Na2O)y(P2O5)1-x-y glasses in the compositional range 0 ≤ x ≤ 0.14 and 0.3 ≤ x + y ≤ 0.4 were studied. For the nearest oxygen shell, the RE-oxygen (RE-O) coordination number decreases from 10.8 to 6.5 with increasing RE content for Pr-, Nd-, Dy-, and Er-doped sodium ultraphosphate glasses. For Eu-doped samples, the Eu-O coordination number was between 7.5 and 8.8. Also, the RE-O mean distance ranges were between 2.43–2.45 Ȧ, 2.40–2.43 Ȧ, 2.36–2.38 Ȧ, 2.30–2.35 Ȧ, and 2.28–2.30 Ȧ for Pr-, Nd-, Eu-, Dy-, and Er-doped samples, respectively.
In the second part, a series of Zr-doped (3–10 mol%) lithium silicate (ZRLS) glass-ceramics and their parent glasses and a series of Zr-doped (2–6 mol% ZrO2) lithium borate (ZRLB) glasses were investigated using Zr K-edge EXAFS and X-ray Absorption Near Edge Structure (XANES) spectroscopy. Immediate coordination environments of all ZRLS glasses are remarkably similar for different compositions. For the nearest oxygen shell, the Zr-O coordination number ranges were between 6.1 and 6.3 for nucleated and crystallized samples, respectively. Also, the Zr-O mean distance remains similar around 2.10 Ȧ. For these glasses, the composition dependence of structural parameters was small. Small changes in the coordination environment were observed for ZRLS glass-ceramics after thermal treatments.
In contrast, Zr coordination environment in ZRLB glasses appear to depend appreciably on the Zr concentration. For the nearest oxygen shell, the Zr-O coordination number increased from 6.1 to 6.8 and the Zr-O distance decreased from 2.18 Ȧ to 2.14 Ȧ with decreasing ZrO2 content.
Recommended Citation
Yoo, Changhyeon, "X-Ray Absorption Spectroscopy Studies Of The Atomic Structure Of Zirconium-Doped Lithium Silicate Glasses And Glass-Ceramics, Zirconium-Doped Lithium Borate Glasses, And Vitreous Rare-Earth Phosphates" (2016). Theses and Dissertations. 2090.
https://commons.und.edu/theses/2090