Sintering behavior and electrochemical properties of garnet-like lithium conductor Li6.25M0.25La3Zr2O12 (M: Al3+ and Ga3+)

• Published in: Solid state ionics 2017-11, Vol.311, p.69-74
• Main Authors: Matsuda, Yasuaki, Sakaida, Asami, Sugimoto, Kaoru, Mori, Daisuke, Takeda, Yasuo, Yamamoto, Osamu, Imanishi, Nobuyuki
• Format: Article
• Language: English
• Subjects: Garnet; Lithium conductor; Low-temperature synthesis; Sintering
• ISSN: 0167-2738; 1872-7689
• DOI: 10.1016/j.ssi.2017.09.014

The sintering behavior and electrochemical properties of garnet-like Li6.25M0.25La3Zr2O12 (M: Al3+ and Ga3+) were investigated. The sintering of Li6.25Al0.25La3Zr2O12 progressed at 1050°C. On the other hand, the densification of Li6.25Ga0.25La3Zr2O12 pellets progressed at lower temperatures above 950°C to yield relative densities of 93.9% after sintering at 1000°C. The temperatures at which the sintering of Li6.25M0.25La3Zr2O12 progressed are in good agreement with the temperatures where the liquid phases of Li-M-O compounds form. The sintering of these compounds was consistent with the change in the lattice parameter due to the replacement of Li+ for Al3+/Ga3+ in the structure. These results suggest that the cation diffusion between the grains and the grain boundaries due to the replacement of Li+ for Al3+/Ga3+ in the garnet-like structure improves the grain growth of these compounds. Dense pellets of Li6.25Ga0.25La3Zr2O12 were obtained by sintering at 1000°C for 12h without the use of mother powders, and the bulk and total conductivities obtained at 25°C were 1.6×10−3 and 9.6×10−4Scm−1, respectively. The activation energies for the bulk and total conductivities were 0.25 and 0.32eV, respectively. Li6.25Ga0.25La3Zr2O12 was stable in contact with lithium metal, even for a long period of 1month. •The sintering of Li6.25Al0.25La3Zr2O12 progressed at 1050°C.•The sintering of Li6.25Ga0.25La3Zr2O12 progressed above 950°C.•The grain growth of these compounds is enhanced at temperatures where the liquid phases of Li-M-O compounds form.•A sintered pellet of Li6.25Ga0.25La3Zr2O12 with a relative density of 93.9% was obtained by sintering at 1000°C for 12 h.•Cubic Li6.25Ga0.25La3Zr2O12 exhibited bulk and total conductivities of 1.6×10−3 and 9.6×10−4 S cm-1, respectively, at 25°C.•Li6.25Ga0.25La3Zr2O12 was stable in contact with lithium metal for a long period of one month.