Fast Na+-ion transport in skeleton structures

Skeleton structures have been explored experimentally for fast Na+-ion transport. A skeleton structure consists of a rigid skeletal array of atoms stabilized by electrons donated by alkali ions partially occupying sites in a three dimensionally linked interstitial space. Fast Na+-ion transport was demonstrated in several structures, and the system Na1+xZr2P3−xSixO12 has a Na+-ion resistivity at 300°C of ϱ300 ≲ 5Ω-cm for x ≈ 2, which is competitive with the best β″-alumina. An activation energy εa ≈ 0.29 eV is about 0.1 eV larger than that of β″-alumina.