71Ga and 69Ga nuclear magnetic resonance study of beta-Ga2O3: resolution of four- and six-fold coordinated Ga sites in static conditions.

71Ga and 69Ga nuclear magnetic resonance (NMR) spectra have been obtained for beta-Ga2O3 at magnetic fields of 11.7 and 7.0 T with a combination of static and spinning samples and using echo techniques. Isotropic chemical shifts and well constrained electric field gradient (EFG) tensors were measured for the GaIV and GaVI sites in beta-Ga2O3 and are reported for the first time. Due to its high quadrupolar coupling constant the GaIV site in beta-Ga2O3 is only resolved in static conditions. Analysis of spectral discontinuities obtained for different isotopes and magnetic field strengths and a method of readily obtaining very broad spectra without point by point acquisition demonstrate an approach that should be very useful in constraining the chemical shifts and quadrupole parameters involved in solid-state gallium NMR spectra.