Phase Analysis of Solid-State Electrolytes (Li<sub>7-x</sub>La<sub>3</sub>Zr<sub>2-x</sub>Ta<sub>x</sub>O<sub>12</sub>) according to Ta Doping Amount via High-Resolution X-Ray Powder Diffraction.
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초록
내용
Garnet-type LLZTO (Li7-xLa3Zr2-xTaxO12, x=Ta doping amount) is a solid electrolyte with a low-conductivity tetragonal and high-conductivity cubic structure. It is well known that it has the tetragonal structure at x=0 (Ta-free) and the cubic structure at x=0.4 (Ta-doped). However, the crystal structure behaviors of LLZTO with compositions between x=0 and x=0.4 are not well understood. Herein, by employing synchrotron XRD, we characterized the crystal structure of LLZTO according to the Ta doping amount (x=0.1, 0.15, 0.2, 0.25, 0.4) through Rietveld refinement. At 0 < x < 0.2, the lattice parameter difference between the tetragonal a- and c-axis is more than 0.5 Å but at 0.2 < x < 0.4, the difference is less than 0.1 Å. This confirms that when Ta is doped, it exists as a pseudo-cubic rather than tetragonal, before becoming a full cubic structure. In future work, we will investigate in detail how these crystallographic features affect the electrochemical properties.