Preliminary Investigation of Flash Sintering of Li_1.5Al_0.5Ge_1.5(PO₄)₃ Solid Electrolyte

Abstract

The effect of alternating current electric field on the densification behavior and microstructural evolution in flash sintering of Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP) is investigated in this study. With an increase in the applied electric field, the onset temperature of flash sintering was lowered and the density of the sintered sample was decreased. Maximum density of 90% was obtained under 50 V_rms/cm and 30 mA_rms/mm². Based on X-ray diffraction results, the crystal phase of the sample has a NASICON-type phase, and no phase transformation was observed in the samples after flash sintering. Spherical-shaped holes were observed in the sample flash-sintered at the higher electric field. A well-developed structure with faceted grains was observed in the high magnification image at the spherical holes. It was suggested that thermal runaway during flash sintering caused a partial melt in the sample while the recrystallization of LAGP from the melt caused the formation of large spherical holes.