Effect of oxygen pressure on structure and ionic conductivity of epitaxial Li0.33La0.55TiO3 solid electrolyte thin films produced by pulsed laser deposition
Leonid A. Bendersky, Bharathi Kamala, Haiyan Tan, Saya Takeuchi, Haoting Shen, Jongmoon Shin, I. Takeuchi
We report on the ionic conductivity and the effect of oxygen partial pressure during the growth of Li0.33La0.55TiO3 (LLTO) epitaxial films grown on SrTiO3 (STO) (100) and (111) substrates and explore some distinct conductivity behavior. The films are intended for fundamental studies of the films behavior as solid electrolytes for all-solid Li-ion batteries. The LLTO films exhibit epitaxial (100) and (111) orientations with perovskite-based structure. Room temperature ionic conductivity of LLTO films grown on STO (100) and STO (111) substrates decrease from 4.3 x 10-5 S/cm to 3.10 x 10-5 S/cm and 1.8 x 10-4 to 2.6 x 10-5 S/cm with increasing oxygen partial pressure (during the film growth) from 1.33 Pa to 26,66 PA,respectively. Real (Z΄) and imaginary (Z΄΄) parts of impedance as a function of frequency at different temperatures show the existence of relaxation processes and their distribution in LLTO films. Complex impedance plots at different temperatures indicate that the conductivity in this material is predominantly due to the intrinsic bulk. dc conductivity of all the LLTO films increases exponentially with increasing temperature. Activation energy (Ea) for all the films were calculated from the temperature dependent conductivity measurements employing the Arrhenius relationship and are seen to be between 0.30 - 0.40 eV, agreeing well with the reported bulk grain activation energy values. LLTO films grown at 1.33 Pa to 26.66 Pa are seen to have conductivity in the order of 10-5 S/cm indicates that these films can be used as a solid electrolyte in high power all solid-state batteries.