Scandium coordination in solid oxides and stabilized zirconia:: 45Sc NMR

Sc-45 NMR isotropic chemical shifts and quadrupole coupling constants of several scandium-containing solid oxides have been measured. Both parameters prove to be sensitive to local structure. In particular, in these materials the Sc-45 isotropic chemical shift appears to be dominated by the first neighbor coordination environment, i.e., the coordination number. The difference in the isotropic shifts between six-coordinated and eight-coordinated scandium is more than 150 ppm, suggesting that this parameter may be especially useful in studying the scandium coordination in oxide materials, disordered solids in particular. Quadrupole coupling constants are sensitive to the nature of the second coordination cation, although many other structural details may play a role. The chemical shift correlation was applied to scandia-stabilized zirconia, (ZrO2)(0.92)(Sc2O3)(0.08), and the mean coordination number obtained appears to be close to seven, which suggests the possibility of two scandium cations pairing with one vacancy.