Proposal Title

Effects of Doped Rare Earth Ions on Encaged Radicals in C12A7:RE3+ A Combination Study of Photoluminescence and EPR Spectroscopy

Primary Faculty Mentor’s Name

Dr. Li Ma

Proposal Track

Student

Session Format

Poster

Abstract

Doped calcium aluminates (12CaO•7Al2O3 or C12A7) (C12A7:Eu3+ and C12A7:Mn2+) have been prepared using solid state reaction methods. The Eu3+ and Mn2+ dopants can both occupy the Ca2+ position of the C12A7 structure. Also, the unique cage-like structure of C12A7 allows superoxides, hydrogen ions and electrons to be trapped within it by changing the preparation or treatment conditions. The effects on these encaged ions/radicals on the local symmetries of Ca2+ have been observed from photoluminescence (PL) spectra of C12A7 doped with Eu3+, and from electron paramagnetic resonance (EPR) spectra of C12A7 doped with Mn2+. Encaged oxygen radicals have shown more distortions to the crystal field of C12A7 than those shown by encaged hydrogen ions or encaged electrons. The changes in the PL spectra can be observed because Eu3+ is a sensitive PL probe for rare earth doping site structure due to its purely magnetic and electric dipole transitions, allowing us to see the difference between superoxide, hydrogen ion, and electron centers. The hyperfine changes in the EPR spectra can be observed because Mn2+ is a sensitive paramagnetic probe, also allowing us to see the difference between the superoxide, hydrogen ion, and electron centers. The effects of different kinds of rare earth dopants (Ce3+, Eu3+, Er3+, and Yb3+) on the paramagnetic properties of the aforementioned encaged radicals, superoxide in particular, have been observed. The EPR spectra for Er3+ or Yb3+ doped C12A7 samples has shown clear broadening when compared to the EPR spectra for un-doped C12A7. Our future work on this topic will focus on investigating the interaction between the rare earth dopants and the encaged ions/radicals in C12A7, especially the effects of the periodic properties of the f-block elements by examining a trend in our observations. A combination of PL and EPR methods will provide efficient tools for the study.

Keywords

Electron spin resonance, Paramagnetic photoluminescence, ESR EPR PL spectroscopy, C12A7, Eu3+, Mn2+, Superoxide hydrogen ion

Location

Concourse/Atrium

Presentation Year

2014

Start Date

11-15-2014 9:40 AM

End Date

11-15-2014 10:55 AM

Publication Type and Release Option

Presentation (Open Access)

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Nov 15th, 9:40 AM Nov 15th, 10:55 AM

Effects of Doped Rare Earth Ions on Encaged Radicals in C12A7:RE3+ A Combination Study of Photoluminescence and EPR Spectroscopy

Concourse/Atrium

Doped calcium aluminates (12CaO•7Al2O3 or C12A7) (C12A7:Eu3+ and C12A7:Mn2+) have been prepared using solid state reaction methods. The Eu3+ and Mn2+ dopants can both occupy the Ca2+ position of the C12A7 structure. Also, the unique cage-like structure of C12A7 allows superoxides, hydrogen ions and electrons to be trapped within it by changing the preparation or treatment conditions. The effects on these encaged ions/radicals on the local symmetries of Ca2+ have been observed from photoluminescence (PL) spectra of C12A7 doped with Eu3+, and from electron paramagnetic resonance (EPR) spectra of C12A7 doped with Mn2+. Encaged oxygen radicals have shown more distortions to the crystal field of C12A7 than those shown by encaged hydrogen ions or encaged electrons. The changes in the PL spectra can be observed because Eu3+ is a sensitive PL probe for rare earth doping site structure due to its purely magnetic and electric dipole transitions, allowing us to see the difference between superoxide, hydrogen ion, and electron centers. The hyperfine changes in the EPR spectra can be observed because Mn2+ is a sensitive paramagnetic probe, also allowing us to see the difference between the superoxide, hydrogen ion, and electron centers. The effects of different kinds of rare earth dopants (Ce3+, Eu3+, Er3+, and Yb3+) on the paramagnetic properties of the aforementioned encaged radicals, superoxide in particular, have been observed. The EPR spectra for Er3+ or Yb3+ doped C12A7 samples has shown clear broadening when compared to the EPR spectra for un-doped C12A7. Our future work on this topic will focus on investigating the interaction between the rare earth dopants and the encaged ions/radicals in C12A7, especially the effects of the periodic properties of the f-block elements by examining a trend in our observations. A combination of PL and EPR methods will provide efficient tools for the study.