A synthesis and crystal chemical study of the fast ion conductor Li 7-3 xGaxLa3 Zr2O12 with x = 0.08 to 0.84

Abstract

Fast-conducting phase-pure cubic Ga-bearing Li7La 3Zr2O12 was obtained using solid-state synthesis methods with 0.08 to 0.52 Ga3+ pfu in the garnet. An upper limit of 0.72 Ga3+ pfu in garnet was obtained, but the synthesis was accompanied by small amounts of La2Zr2O12 and LiGaO3. The synthetic products were characterized by X-ray powder diffraction, electron microprobe and SEM analyses, ICP-OES measurements, and 71Ga MAS NMR spectroscopy. The unit-cell parameter, a0, of the various garnets does not vary significantly as a function of Ga 3+ content, with a value of about 12.984(4) Å. Full chemical analyses for the solid solutions were obtained giving: Li7.08Ga 0.06La2.93Zr2.02O12, Li 6.50Ga0.15La2.96Zr2.05O 12, Li6.48Ga0.23La2.93Zr 2.04O12, Li5.93Ga0.36La 2.94Zr2.01O12, Li5.38Ga 0.53La2.96Zr1.99O12, Li 4.82Ga0.60La2.96Zr2.00O 12, and Li4.53Ga0.72La2.94Zr 1.98O12. The NMR spectra are interpreted as indicating that Ga3+ mainly occurs in a distorted 4-fold coordinated environment that probably corresponds to the general 96h crystallographic site of garnet. © 2014 American Chemical Society.