Glass-ceramic Na fast ionic conductors based upon Na3+3x-yR1-xPySi3-yO9 were prepared, where R represented various rare-earths. It was found that the possible combinations of x and y became more limited, with regard to successful crystallization of the fast ionic conducting phase, as the ionic radius of R increased. On the other hand, the Na-conducting properties were enhanced in glass-ceramics where R had a large ionic radius.

K.Yamashita, T.Umegaki, M.Tanaka, T.Kakuta, T.Nojiri: Journal of the Electrochemical Society, 1996, 143[7], 2180-5