Temperature calibration for high-temperature MAS NMR to 913 K: 63Cu MAS NMR of CuBr and CuI, and 23Na MAS NMR of NaNbO3.

Abstract The solid-state phase transitions of CuBr, CuI and NaNbO 3 can be readily observed using 63 Cu and 23 Na high-temperature magic-angle spinning nuclear magnetic resonance spectroscopy. Temperature has large, linear effects on the peak maximum of 63 Cu in each solid phase of CuBr and CuI, and there is large jump in shift across each phase transition. The 23 Na MAS NMR peak intensities and the line widths in NaNbO 3 also clearly show its high-temperature transition to the cubic phase. These data can be used to calibrate high-temperature MAS NMR probes up to 913 K, which is two hundred degrees higher than the commonly-used temperature calibration based on the chemical shift of 207 Pb in Pb(NO 3 ) 2 .