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Separation of quadrupolar and paramagnetic shift interactions with TOP-STMAS/MQMAS in solid-state lighting phosphors
José P Carvalho1, Aleksander Jaworski1, Michael J Brady2
1Department of Materials and Environmental Chemistry, Stockholm University, Stockholm, Sweden.
Magnetic Resonance in Chemistry : MRC
|January 31, 2020
Summary
A novel processing method enhances solid-state nuclear magnetic resonance (NMR) analysis of paramagnetic materials. This technique improves spectral resolution for satellite-transition magic-angle spinning (STMAS) and multiple-quantum magic-angle spinning (MQMAS) data.
Area of Science:
- Solid-state Nuclear Magnetic Resonance (NMR) Spectroscopy
- Materials Science
- Quantum Chemistry
Background:
- Paramagnetic systems present challenges in NMR spectroscopy due to inhomogeneous broadening.
- Conventional processing of STMAS and MQMAS spectra has limitations in spectral width.
- Accurate characterization of local structures in doped materials is crucial.
Purpose of the Study:
- To introduce a new processing approach for STMAS and MQMAS data.
- To overcome limitations of conventional spectral processing in paramagnetic systems.
- To accurately determine quadrupolar parameters and understand local structures in lanthanide-doped YAGs.
Main Methods:
- Development of a processing method based on the two-dimensional one-pulse (TOP) technique.
- Application of a double shearing transformation to separate quadrupolar anisotropy and paramagnetic shift interactions.
- Experimental application to Al-27 solid-state NMR of lanthanide-doped Yttrium Aluminum Garnets (YAGs).
Main Results:
- Successful separation of second-rank quadrupolar anisotropy and paramagnetic shift interactions.
- Overcoming the spectral width limitation in the indirect dimension of MQMAS and STMAS.
- Extraction of quadrupolar parameters for both shifted and unshifted Al sites in doped YAGs.
Conclusions:
- The new TOP-based method provides enhanced spectral resolution for paramagnetic systems.
- The extracted quadrupolar parameters aid in understanding the local structure of lanthanide substituents in YAG.
- Integration with DFT calculations offers deeper insights into material properties.
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