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

•Li-ion conducting garnet-type Li6BaLa2Ta2O12 was prepared.•Li6BaLa2Ta2O12 was deposited for the first time as thin film by PLD.•The electric conductivity of bulk and thin film garnets is compared.•The electronic conductivity of LBLTO is studied by Hebb-Wagner polarization

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 MgO(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 σ = 5.0 ⋅ 10− 5 S cm− 1 at 25 °C, whereas the Li6BaLa2Ta2O12 garnet-type films exhibit a lower conductivity of σ = 2 ⋅ 10− 6 S cm− 1 at 25 °C, which is comparable to the ionic conductivity of LiPON being about σ = 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 σel = 2.87 ⋅ 10− 13 S cm− 1 and σel = 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 tel = 5.74 ⋅ 10− 9 and tel = 6.76 ⋅ 10− 6.