Synthesis and Physico-Chemical Characterizations of the Lithium-Substituted NASICONS Series with General Formula Li_2.8Zr_2−ySi_1.8−4yP_1.2+4yO₁₂ where (0 ≤ y ≤ 0.45)

The lithium-substituted NASICONS materials, with general formula Li_2.8Zr_2−ySi_1.8−4yP_1.2+4yO₁₂ where 0 ≤ y ≤ 0.45, were synthesized by the sol–gel method which consisted in calcinig the preliminary precursors at temperatures higher than their crystallization temperatures. The calcined powders have been characterized by physico-chemical techniques: coupled DTA-TGA, XRD and CIS. The coupled DTA-TGA was used to determine the crystallization temperatures and leading to the estimation of the calcined temperatures. The XRD analyses show the obtaining of only the single phase without any detection of other phases as: ZrO₂, SiO₂, Li₂O, ZrSiO₄, Li₃PO₄, Li₂SiO₃ or Li₂ZrO₃, according to their JCPDS file cards and suggest that the decrease in the zirconium concentration does not modify the stability of the lithium-substituted NASICONS, whereas the complex impedance spectroscopy results have highlighted the best total electric conductivity for y value equal to 0.225.