Wednesday, May 10, 2006

JPC B, Ashbrook and Farnan, 89Y MAS NMR of Y2Ti2-xSnxO7 Pyrochlores

J. Phys. Chem. B, ASAP Article 10.1021/jp060844q S1520-6106(06)00844-3

89Y Magic-Angle Spinning NMR of Y2Ti2-xSnxO7 Pyrochlores

Sharon E. Ashbrook,* Karl R. Whittle, Gregory R. Lumpkin, and Ian Farnan

School of Chemistry and EaStCHEM, University of St. Andrews, North Haugh, St. Andrews KY16 9ST, U.K., and Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, U.K.


The yttrium local environment in the series of pyrochlores Y2Ti2-xSnxO7 was studied using 89Y NMR. Oxides with the pyrochlore structure exhibit a range of interesting physical and chemical properties, resulting in many technological applications, including the encapsulation of lanthanide- and actinide-bearing radioactive waste. The use of the nonradioactive Y3+ cation provides a sensitive probe for any changes in the local structure and ordering with solid solution composition, through 89Y (I = 1/2) NMR. We confirm that a single pyrochlore phase is formed over the entire compositional range, with Y found only on the eight-coordinated A site. A significant (~15 ppm) chemical shift is observed for each Sn substituted into the Y second neighbor coordination environment. The spectral signal intensities of the possible combinations of Sn/Ti neighbors match those predicted statistically assuming a random distribution of Sn4+/Ti4+ on the six-coordinated pyrochlore B site.

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