Enhanced Li⁺ Ionic Conduction and Relaxation Properties of Li_5+2xLa₃Ta_2-xGa_xO₁₂ Garnets

Abstract

In the current work, we studied the effect of Ga+3 substitutions on the Ta+5 sites in Li5+2xLa3Ta2-xGaxO12 (LLT-Ga) lithium conducting garnets (with x = 0.1–0.5) in order to enhance the ionic conductivity of these materials. The current materials are prepared by solid state reaction and their electrical properties are studied by impedance spectroscopy measurements. XRD data showed that cubic garnet phases are obtained for LLT-Ga garnets. The ionic conductivity increased by one order of magnitude for x = 0.3 composition with a value of ~4 × 10−5 S/cm compared to that of Li5La3Ta2O12 material. Moreover, the hopping frequency and the concentration of mobile Li+ ions were estimated from analysis of the conductivity spectra, and it was found that both the concentration and mobility of Li+ ions increased with increasing Ga+3 content in the materials. The dielectric and relaxation properties were studied in the dielectric permittivity and electric modulus formalisms. The current materials exhibited giant values of the dielectric constant of ε′ ~ 6500, originating from internal effects in the materials.

Keywords

• lithium conducting garnets
• ionic conduction
• conductivity relaxation
• dielectric properties