| 研究実績の概要 |
Lithium garnet-type oxides Li7-xLa3Zr2-xNbxO12 (LLZNbO, x=0-1) were prepared by a sol-gel process at low temperatures. Then, glass additives, LiO2-B2O3-SiO2 glass and BaO-B2O3-SiO2 glass, were used to stimulate the sintering of the ceramic electrolyte retaining the cubic phase stable at low temperatures.
The cubic garnet phase was formed by a heat-treatment of sol-gel derived precursor powders at 600 - 700 degree C. The presursor powders and glass additives, 53LiO2･31B2O3･12SiO2 (mol%) (LiO2-B2O3-SiO2 glass) or 35BaO･10CaO･5Al2O3･15B2O3･10SiO2 (mol%) (BaO-B2O3-SiO2 glass) were pressed into pellets and sintered at 900 degree C.
The relatative density of 86% was achieved by the sintering with glass additives at 900 degree C. In the composites sintered with the BaO-B2O3-SiO2 glass, the presence of La2Zr2O7 was detected at concentration higher of 4 wt%, while the single cubic phase was obtained for the composites sintered with the LiO2-B2O3-SiO2 glass.
The ionic conductivity of the obtained composite was 8x10^-5 S/cm at 30 degree C using 4 wt.% of LiO2-B2O3-SiO2 glass. The conductivity is 20% lower than the material reported by the solid state reaction process, but the heat treatment used is about 300 degree C lower than that required by the conventional solid state reaction process. This represents an important contribution to further application of the LLZNbO solid electlolyte to all-solid-state battery.
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