Fabrication of garnet solid electrolytes via sputtering for solid-state batteries

Abstract

In this study, the deposition of Li₇La₃Zr₂O₁₂ (LLZO) thin films onto MgO substrates was successfully achieved using the radio frequency magnetron sputtering technique. The deposition process was carried out at various substrate temperatures to investigate their influence on the film properties The as-deposited films were initially amorphous; however, they could be crystallized into the cubic phase by increasing the deposition temperature above 100 °C. Upon raising the deposition temperature to 200 °C, the peaks in the X-ray diffraction pattern became sharper and more intense, indicating an increase in the volume fraction and crystallite size of LLZO. At 200 °C, the film consisted predominantly of the conductive crystalline LLZO phase, resulting in a remarkably high ionic conductivity of about 10⁻⁴ S cm⁻¹. The film deposited at 300 °C exhibited the second phase, i.e., the La₂Zr₂O₇ phase, which resulted from excessive lithium losses. These findings highlight the importance of controlling the deposition temperature to achieve the desired crystalline phase and optimize the electrical properties of LLZO thin films.