New trivalent cationic conductors with a NASICON-type structure of the form, R1/3Zr2(PO4)3 (where R was a rare earth), were prepared by using a sol-gel method. It was found that, with increasing R3+ radius, the lattice expanded and the conductivity decreased. The compound Sc1/3Zr2(PO4)3, which contained the smallest trivalent cation in the rare-earth series, exhibited the highest conductivity; as expected from the relationship between the migrating cation size and the lattice volume. Trivalent Sc3+-ion conduction in the corresponding solid electrolyte was demonstrated directly by means of direct-current electrolysis.

Trivalent Cation Conduction in R1/3Zr2(PO4)3 with the NASICON-Type Structure. S.Tamura, N.Imanaka, G.Adachi: Journal of Alloys and Compounds, 2001, 323-324, 540-4