Fast-Ion Transport in the NASICON Analog Na sub 3 Sc sub 2 (PO Sub 4 ) sub 3 : Structure and Conductivity

摘要

The room temperature modification of stoichiometric NASICON(Sc) is monoclinic Cc. At 64 exp 0 C there is a first order transition to a normal-conducting rhombohedral form R anti 3c. Na(1) sites are fully occupied whereas Na(2) sites are partially occupied. At 167 exp 0 C there is a transition to a superionic phase, but the structure remains rhombohedral R anti 3c. Vacancies are now shared equally by Na(1) and Na(2) sites. Fast Na-ion motion in stoichiometric Na sub 3 Sc sub 2 (PO sub 4 ) sub 3 arises from vacancy motion in a dogleg path between Na(1) and Na(2) sites. (ERA citation 08:041640)