Synthesis and conductivity studies of Li1.5Al0.5Ge1.5(PO4)3 solid electrolyte

This paper describes the preparation of a lithium ion conducting solid electrolyte with the composition Li1.5Al0.5Ge1.5(PO4)3 by a new liquid-phase method with the use of the water-soluble salts Al(NO3)3 · 9H2O, LiNO3 · 3H2O, and (NH4)2HPO4 and the germano-oxalic acid H2[Ge(C2O4)3]. The synthesized materials have been characterized by X-ray diffraction, differential scanning calorimetry, thermogravimetry, and impedance spectroscopy. The results demonstrate that sintering of the synthesized amorphous powders at a temperature of 650°C leads to the formation of phase-pure Li1.5Al0.5Ge1.5(PO4)3. The ionic conductivity of the electrolyte measured at frequencies from 10 Hz to 2 MHz using pellets with an 86% relative density was 4.2 × 10–4 S/cm.