NMR investigation of mechanically milled nanostructured GaF3powders

High-energy ball milling is suitable for the preparation of nanostructured powders. First, high-resolution, solid-state nuclear magnetic resonance (NMR) investigations of 19 F, 69 Ga and 71 Ga in ball-milled ionic GaF 3 are presented. The quadrupolar parameter and the isotropic chemical shift distributions are determined for the three nuclei. The quadrupolar parameter distributions give clear evidence of two main structurally different phases in mechanically milled GaF 3 . A discussion based upon molecular dynamics simulations allows us to distinguish these two phases according to the size of the distortion of the GaF 6 octahedral units: the lowest distortion is related to crystalline grains and the highest one to grain boundaries. It is thus concluded that NMR is a technique well adapted to the quantification and characterization of these two phases.