Phase evolution during reactive flash sintering of Li6.25Al0.25La3Zr2O12 starting from a chemically prepared powder

摘要

Reactive flash sintering (RFS) of a chemically prepared multiphase precursor powder was performed to fabricate Li6.25Al0.25La3Zr2O12 (Al-LLZO) ceramics. This approach allowed for obtaining single-phase dense samples in a remarkably short processing time of 30 s, at a furnace temperature of 600 ?C, with an electric field of 50 V cm-1 and a current limit of 150 mA mm-2. The ceramics display high bulk conductivity of 0.18 mS cm-1 at room temperature. Furthermore, phase evolution is studied by in-situ X-ray diffraction during: i) conventional heating and ii) RFS under current rate mode. As expected, the intermediate phases progressively dissolved into the AlLLZO matrix by conventional heating. On the other hand, RFS promoted the growth of the intermediate La2Zr2O7, an effect that was overcome by the thermally driven formation of Al-LLZO at higher temperatures. The observed different reaction pathway suggests that RFS can be used for stabilizing phases that are not thermodynamically favored upon conventional heating.