Preparation and electrical properties of garnet-type Li6BaLa2Ta2O12 lithium solid electrolyte thin films prepared by pulsed laser deposition

The growth of Li-ion conducting Li6BaLa2Ta2O12 garnet-type thin films by pulsed laser deposition (PLD) is reported. Li6BaLa2Ta2O12 was synthesized as target material by a high temperature solid-state reaction. Thin films were grown on Mg0(100) by ablation of the respective bulk target material consisting of Li6BaLa2Ta2O12 with 5 mol% excess of Li2O to compensate lithium loss during thin film growth. X-ray diffraction revealed a garnet-type structure of the prepared thin films. The bulk material showed electrical conductivity of up to sigma= 5.0 . 10(-5) S cm(-1) at 25 C, whereas the Li6BaLa2Ta2O12 garnet-type films exhibit a lower conductivity of a = 2 . 10(-6) S cm(-1) at 25 C, which is comparable to the ionic conductivity of UPON being about sigma = 2 . 10(-6) S cm(-1) at the same temperature. The activation energy Ea of bulk and thin film samples results in 0.44 eV and 0.42 eV, respectively, as determined by temperature-dependent conductivity measurements. Ohara glass-ceramic was successfully protected against reduction by deposition of a thin garnet-type film on top of the glass ceramic. The partial electronic conductivity of the bulk material was determined by the Wagner-Hebb-polarization technique. The electronic partial conductivity took values between sigma(e1) = 2.87 .10(-13) S cm(-1) and sigma(e1) = 3.47 . 10(-10) S cm(-1) in the range of the polarization voltage U = 2.8 V to U = 4.3 V, resulting in low electronic transference numbers between t(e1) = 5.74 . 10(-9) and t(el) = 6.76 .10(-5). (c) 2014 Elsevier B.V. All rights reserved.