SOLID-STATE PB-207 NMR OF LEAD(II) NITRATE - LOCALIZED HEATING EFFECTS AT HIGH MAGIC-ANGLE-SPINNING SPEEDS

Solid-state Pb-207 NMR spectra of lead(II) nitrate were found to be hi ghly sensitive to variations in temperature. The Pb-207 chemical shift exhibits a linear dependence on temperature with a positive slope of 0.70 +/- 0.02 ppm K-1, i.e. increases in temperature cause a change in chemical shift to higher frequency. This slope is within experimental error of the value obtained from parallel experiments on the static s olid, 0.72 +/- 0.06 ppm K-1. At higher magic angle spinning (MAS) spee ds and ambient probe temperature, the Pb-207 signal splits into severa l components owing to localized heating effects. These effects are mor e pronounced in rotors made from partially stabilized zirconia than th ose made from silicon nitride and are attributed to the poorer thermoc onductive properties of the zirconia ceramic. In the zirconia rotors, discrete thermal regions within the lead(II) nitrate sample were locat ed and differ by 5 K at 12 kHz MAS speeds. The response of the Pb-207 lead(II) nitrate signal to temperature variation suggests that it coul d be used for calibrating solid-state NMR probes.