ZR-91 NUCLEAR-QUADRUPOLE COUPLING IN ZIRCON (ZRSIO4)

The first measurement of 91Zr nuclear quadrupole coupling in a solid is reported. The nuclear quadrupole coupling constant (e2qQ/h) and chemical shift anisotropy ( sigma ax) for 91Zr, and the chemical shift anisotropy for 29Si, have been determined for zircon (ZrSiO4) from high-field NMR single-crystal rotation patterns. A striking variation of 91Zr linewidth with crystal orientation in the field was observed and explained in terms of local variations in the (001) tetragonal axis orientation due to crystal mosaic structure as well as a distribution of local electric-field gradients due to defects.