Structural characterization of fluorophosphate glasses using NMR methodologies

Author(s)

Raphaell Júnnio Moreira Silva

• Document type: Master's Dissertation
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Instituto de Física de São Carlos (IFSC/BT)
• Defense date: 2014-06-09

Examining board members

Hellmut Eckert; Ubirajara Pereira Rodrigues Filho; José Fábian Schneider

• Advisor: Hellmut Eckert

Abstract

In this work was studied the development of structure/property correlations for new fluorophosphate glasses compositions: [80Ba(PO3)2 - 20Al(PO3)3]1-x[80BaF2 - 20AlF3]x(0 ≤ x ≤ 40 - mol%). Most suitable techniques for the structural analysis in case of disordered and amorphous material are Nuclear Magnetic Resonance (NMR) Spectroscopy and Raman scattering. Results from X-ray diffraction (XRD) and differential thermal analysis (DTA) reveal that amorphous samples were obtained for all glass compositions up to x ≤ 30. However, the fluorine quantification via 19F MAS NMR suggests significant fluoride loss and/or fluoride/oxide replacement. Both 31P and Raman results indicate gradual conversion of Q2m units to Q1m units with increasing the fluorine concentration. 19F MAS NMR spectra indicate fluorine atoms in two different chemical environments bonded wither covalently to P-atoms or located in a mixed Al/Ba environment. The P-F assignment is confirmed by 19F{31P}-REDOR experiments. 27Al NMR spectra shows dominantly six-coordinated aluminium, and the 27Al{31P}-REDOR data suggest nearly exclusive coordination of Al with phosphate species. The dipolar coupling constant obtained by 31P{31P}-DRENAR are roughly consistent with 31P spectral deconvolution suggesting the presence of Q1and Q2 species. (AU)

• FAPESP's process: 12/16297-0 - The effect of fluoride ions on the local environment of rare-earth dopants in luminescent oxyfluoride glasses and ceramics: structural studies by magnetic resonance methods
• Grantee: Raphaell Junnio Moreira Silva
• Support Opportunities: Scholarships in Brazil - Master