NASICON-type compounds with the formula, Na3Si2Zr1.88Y0.12O12, were prepared so as have various microstructures. The samples were fired at 1190 to 1235C, for 2 to 80h. The results revealed an appreciable effect of the processing conditions upon the microstructure; which altered both the grains and grain boundaries. It was found that the conductivity was controlled mainly by the grain boundary contribution, which depended

strongly upon the grain size and the density of grain boundaries. A maximum conductivity of about 0.0027S/cm at room temperature was found for samples that had been sintered at 1220C for 40h.

Influence of Microstructure on the Electrical Properties of NASICON Materials. R.O.Fuentes, F.M.Figueiredo, F.M.B.Marques, J.I.Franco: Solid State Ionics, 2001, 140[1-2], 173-9