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Illustration of the studied glass ceramics in this work
Illustration of the studied glass ceramics in this work

Andris Antuzevics defend PhD thesis "Local Structure of s-State Rare Earth Ions in Fluorides and Oxyfluoride Glass Ceramics"

06.12.2017

December 12, at 11:00 Zellu Street 25, 233 auditorium

In this work local structure of S-state rare earth ions (Gd3+ and Eu2+) is investigated with electron paramagnetic resonance (EPR) spectroscopy technique in ScF3 and BaY2F8 single crystals as well as in oxyfluoride glass ceramics containing MeF2 (Me = Ca, Ba, Sr) crystallites.

EPR spectra parameters at different temperatures for gadolinium in ScF3 – crystal with negative thermal expansion coefficient – indicate a positive expansion of the centre local structure with temperature. The Gd3+ centre of BaY2F8 crystal can be described with a set of low symmetry EPR spectra parameters.

As S-state ions embed the crystalline phase of oxyfluoride glass ceramics, the glassy U-type spectrum is superimposed by an intensive EPR spectra fine structure at g = 1.99. Good agreement between the experimental and simulated spectra can be achieved by taking the defect centre parameters of the corresponding single crystals. EPR spectra of glass ceramics with europium contain information about the valence state of ions as well as Eu2+ local structure.