Methylammonium lead chloride: A sensitive sample for an accurate NMR thermometer

A new solid-state nuclear magnetic resonance (NMR) thermometry sample is proposed. The Pb-207 NMR chemical shift of a lead halide perovskite, methylammonium lead chloride (MAPbCl(3)) is very sensitive to temperature, 0.905 +/- 0.010 ppm K-1. The response to temperature is linear over a wide temperature range, from its tetragonal to cubic phase transition at 178 K to >410 K, making it an ideal standard for temperature calibrations in this range. Because the 207Pb NMR lineshape for MAPbCl(3) appears symmetric, the sample is ideal for calibration of variable temperature NMR data acquired for spinning or non spinning samples. A frequency-ratio method is proposed for referencing 207Pb chemical shifts, based on the H-1 and C-13 frequencies of the methylammonium cation, which are used as an internal standard. Finally, this new NMR thermometer has been used to measure the degree of frictional heating as a function of spinning frequency for a series of MAS rotors ranging in outer diameter from 1.3 to 7.0 mm. As expected, the largest diameter rotors are more susceptible to frictional heating, but lower diameter rotors are subjected to higher frictional heating temperatures as they are typically spun at much higher spinning frequencies. (C) 2017 Elsevier Inc. All rights reserved.