Synthesis and characterization of substituted garnet and perovskite-based lithium-ion conducting solid electrolytes

Titanium, tantalum-substituted Li(7)La(3)Zr(2-x)A(x)O(12) (LLZO, A=Ta, Ti) garnets, and chromium-substituted La(2/3)-xLi3xTi1-yCryO3 (LLTO) perovskites were prepared by a conventional solid-state reaction and the Pechini processes. The desired crystal phases were obtained by varying the calcination temperature and time, as well as the substitution concentration. All samples indicated decomposition of the precursors when heated above 750 degrees C and formation of the desired phase after heat treatment at higher temperatures. Neutron diffraction data shows the formation of a predominant cubic phase in the case of Ta-LLZO, and monoclinic phase with minor impurity phases for Cr-LLTO. Ionic conductivity for Ti-LLZO (Li7La3Zr1.Ti-4(0).O-6(12)), Ta-LLZO (Li6.03La3Zr1.533Ta0.46O12), and Cr-LLTO (La(2/3)-xLi3xTi0.9Cr0.1O3) at room temperature were found to be 5.21x10(-6), 1.01x10(-6), and 1.2x10(-4) S cm(-1), respectively. The activation energies of the compounds were determined from the Arrhenius plot and were 0.44 eV (Ti-0.6-LLZO), 0.54 eV (Ta-0.5-LLZO), and 0.20 eV (Cr-0.1-LLTO).