Sol-Gel Synthesis, Sintering And Electrical Properties Of Nasicon Having New Compositions, Na3zr2-(X/4)Si2-Xp1+Xo12

Powders and pellets of new NASICON compositions have been synthesized using a mixed inorganic-organic sol-gel synthesis, by the preliminary formation of a pre-hydrolized TEOS xerogel. The investigated compositions can be described by the general formula Na3Zr2-(x/4)Si2-xP1+xO12 obtained by keeping constant (= 3) the Na concentration at the optimum value reported for ionic conductivity, with x = 0 (the usual NASICON composition), 0.667, and 1.333. The xerogels were calcined at various temperatures in the range 400-800 degrees C. The samples were analyzed by TG/DTA, BET measurements, XRD, EDS, and SEM. The powders were sintered into pellets at 1100 degrees C. The sinterability increased with increasing the x value. This is attributed to the presence of a glassy phase and the occurrence of liquid phase sintering. The electrical conductivity of the NASICON sintered bodies, measured by a.c. impedance spectroscopy, is correlated with the lattice parameters of the hexagonal structure, and increased with increasing the x value.