IONIC-CONDUCTIVITY OF THE NA1+XM-X(111)ZR2-X(PO4)3 SYSTEMS (M = AL, GA, CR, FE, SC, IN, Y, YB)

The existence and ionic conductivity of solid solutions Na1+xMxIIIZr2-x(PO4)3 with Nasicon-like structure have been investigated and the results compared with literature data. A limited range of solid solutions is formed with MIII = aluminium, gallium, yttrium, ytterbium, whereas a continuous series is obtained for MIII = chromium, iron, scandium, indium. The pure end member Na3ln2(PO4)3 is reported for the first time; according to powder diffraction data, it is hexagonal with a = 0.8966(1) and c = 2.2104(4) nm. The small monoclinic distortion already known for MIII = chromium, iron and scandium is restricted to x values very close to 2. Ionic conductivity measurements show that for a given value of x, the mobility of the Na+ ions is strongly influenced both by the ionic radius and the type of electronic structure of the MIII ion. However, no simple correlation can be found. © 1990 Chapman and Hall Ltd.