Chem. Mater. 45Sc NMR of Solid Oxides and Stablized Zirconia, Stebbins

Chem. Mater., 18 (16), 3855 -3859, 2006. 10.1021/cm060590lS0897-4756(06)00590-4
Web Release Date: July 7, 2006

Scandium Coordination in Solid Oxides and Stabilized Zirconia: ⁴⁵Sc NMR

Namjun Kim, Cheng-Han Hsieh, and Jonathan F. Stebbins

Departments of Geological and Environmental Sciences and Materials Science and Engineering, Stanford University, Stanford, California 94305

Abstract:

⁴⁵Sc 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 ⁴⁵Sc 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.