On the Possibility of Increasing the Ionic Conductivity of Ceramics Based on Lithium Titanium Phosphate with the NASICON Structure

In this work, a synthesis technique has been developed that made it possible to obtain highly conductive ceramics based on lithium–titanium phosphate of the composition Li1.2Al0.2Ge0.2Ti1.6(PO4)3 with a relative density of 97% and lithium-ion conductivity up to 1.4 × 10–3 S/cm at room temperature. It consisted of two successive high-temperature annealings with intermediate mechanochemical treatment of the precursor. Using impedance spectroscopy, it was shown that the value of the total lithium-ion conductivity approaches its bulk conductivity for this material. This conclusion is confirmed by NMR method with pulsed magnetic field gradient. The good sintering of the ceramics and its high density result in the suppression of grain boundary resistance, which negatively affects the conductive properties of most materials with the NASICON structure.