MAS-NMR at very high temperatures

Area of Science:

• Solid-state chemistry
• Materials science
• Spectroscopy

Background:

• High-temperature solid-state Nuclear Magnetic Resonance (NMR) is crucial for understanding material properties under extreme conditions.
• Previous MAS-NMR studies were limited by the challenges of achieving and accurately measuring temperatures above 1000 K.

Purpose of the Study:

• To develop and validate a method for performing MAS-NMR experiments at temperatures approaching 1200 K.
• To establish a reliable internal thermometer for accurate temperature measurement in high-temperature MAS-NMR.

Main Methods:

• Utilized a carbon dioxide (CO(2)) laser as the primary heating device for the MAS-NMR probe.
• Developed an internal NMR thermometer leveraging the temperature-dependent spin-lattice relaxation (T1) data of Lithium lanthanum titanate (Li(0.24)La(0.54)TiO(3)).
• Calibrated the temperature using the known melting point of Lithium borate (Li(2)B(4)O(7)) at 1191 K, monitored via (7)Li-MAS-NMR.

Main Results:

• Successfully achieved and maintained stable temperatures up to 1191 K under MAS conditions.
• Demonstrated the accuracy of the internal NMR thermometer by correlating it with the melting point of Li(2)B(4)O(7).
• Successfully followed the phase transition (melting) of Li(2)B(4)O(7) using (7)Li-MAS-NMR at 1191 K.

Conclusions:

• The developed CO(2) laser heating system combined with the (7)Li-based NMR thermometer enables reliable high-temperature MAS-NMR studies.
• This methodology opens new avenues for investigating material behavior and phase transitions at extreme temperatures using NMR spectroscopy.