Solid-state NMR study of the anionic conductor Ca-doped Y2Ti2O7

Abstract

Doping the pyrochlore (Y₂Ti₂O₇) with the Ca²⁺ has been reported to improve the oxygen ionic conductivity (S. Kramer, M. Spears and H. L. Tuller, Solid State Ionics, 1994, 72, 59–66). ¹⁷O and ⁸⁹Y solid-state NMR has been used in work reported here to probe the local environment of the oxygen and yttrium sites in these materials. Although the conductivity of these materials is only moderate, variable-temperature, one-dimensional ¹⁷O NMR experiments and two-dimensional ¹⁷O magnetization exchange spectroscopy show that oxygen-ion jumps occur between the oxygen sites nearby titanium. Motion at ambient temperatures involves the O1 and local environments created by the Ca²⁺ doping; motion does not involve the O2 oxygen site coordinated to four yttrium ions.