Electrical properties of sol–gel processed NASICON having new compositions

High-conductivity and high-density samples with new compositions in the NASICON-type electrolyte series, i.e., the Na3Zr2−(x/4)Si2−xP1+xO12 system, with x=0(A), 0.667(B), and 1.333(C) were synthesized using a mixed inorganic–organic sol–gel process. The sinterability was improved with increasing the x value, but the conductivity decreased. Highly dense samples were obtained by sintering at 1100°C. The conductivity decreased with decreasing the c lattice parameter of the hexagonal structure. Nevertheless, the CO2 gas sensors using the highly dense B and C samples showed good EMF response which is very close to the theoretical value.