CRYSTAL-CHEMISTRY AND IONIC-CONDUCTIVITY OF SOLID-SOLUTIONS AGTI2-XZRX(PO4)3 AND AG1+XTI2-XMX(PO4)3 WITH MIII=SC,FE)

In order to obtain good solid silver ion conductors, Nasicon-type solid solutions have been prepared: AgTi2-xZrx(PO4)3 by direct synthesis and Ag1+xTi2-xMx(PO4)3 (M = Sc,Fe) by cationic exchange reaction from the Na homologous phases. Every solid solution is continuous for 0 less-than-or-equal-to x less-than-or-equal-to 2. The phase "Na-Ti-Fe" is monoclinic-pseudo rhombohedral, all others are rhombohedral (R3cBAR). At 300-degrees-C the maximum sigma-value is 8.10(-2) S.cm-1 and the minimum E(a)-value is 0.20 eV for the solid solution "Ag-Ti-Sc". Variations of ionic conductivity appear essentially correlated with the size of "bottlenecks" and the concentrations of silver and empty sites in the structure.