Phase evolution during reactive flash sintering of Li6.25Al0.25La3Zr2O12 starting from a chemically prepared powder. Issue 8 (July 2021) - Avila, Viviana
Highlights: Li6.25 Al0.25 La3 Zr2 O12 ceramics were produced by reactive flash sintering (RFS), starting from a chemically prepared precursor powder. Single-phase dense samples were obtained in just 30 s with an electric field of 50 V cm −1 and a current limit of 150 mA mm −2 . The ceramics displayed the cubic garnet structure and a bulk ionic conductivity of 0.18 mScm −1 at room temperature. Phase evolution during RFS is studied by in-situ synchrotron XRD and compared with conventional heating processing. Reaction pathway during RFS is different, which can be used for stabilizing phases that are not thermodynamically favored. Abstract: Reactive flash sintering (RFS) of a chemically prepared multiphase precursor powder was performed to fabricate Li6.25 Al0.25 La3 Zr2 O12 (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 Al-LLZO matrix by conventional heating. On the other hand, RFS promoted the growth of the intermediate La2 Zr2 O7, 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.