Oxygen ion conductivity of (Yb0.9-x Tb (x) Ca-0.1)(2)Ti2O7-delta solid solutionsстатья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:We have studied terbium substitution for ytterbium in (Yb0.9 - x Tb (x) Ca-0.1)(2)Ti2O7 - delta (x = 0.1, 0.2, 0.3, 0.4) pyrochlore solid solutions synthesized through coprecipitation followed by firing at 1550A degrees C. The results indicate that only a small amount of terbium (less than 10%) can be incorporated into the pyrochlore structure of (Yb0.9Ca0.1)(2)Ti2O6.9 because of the large difference in ionic radius between the terbium and ytterbium cations: Delta r = r(Tb (CN 8) (3+) ) - r(Yb (CN 8) (3+) ) = 0.055 . The oxygen ion conductivity of the (Yb0.9 - x Tb (x) Ca-0.1)(2)Ti2O7 - delta solid solutions has been determined by impedance spectroscopy in air in the temperature range 300 to 900A degrees C. At high temperatures (t > 640A degrees C), their bulk conductivity was essentially independent of the Yb/Tb ratio. The observed decrease in density and microstructural changes were insignificant. At relatively low temperatures (t < 640A degrees C), the bulk conductivity decreased slightly, and the decrease depended little on terbium concentration.