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Fabrication of Li1+xAlxGe2-x(PO4)3 thin films by sputtering for solid electrolytes

DOI: 10.1016/j.ssi.2020.115397 DOI Help

Authors: T. Mousavi (University of Oxford; The Faraday Institution) , X. Chen (Shanghai Jiao Tong University) , C. Doerrer (University of Oxford) , B. Jagger (University of Oxford) , S. C. Speller (University of Oxford; The Faraday Institution) , C. R. M. Grovenor (University of Oxford; The Faraday Institution)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Solid State Ionics , VOL 354

State: Published (Approved)
Published: October 2020
Diamond Proposal Number(s): 21686

Abstract: Li1+xAlxGe2-x(PO4)3 (LAGP) thin films have been grown on sapphire substrates by RF magnetron sputtering and post annealing. The effects of varying sputtering parameters such as power and pressure were studied, and the deposited films were characterized to investigate how the ionic conductivity values depend on the microstructure. The composition of as-sputtered films was found to be more strongly influenced by power than the pressure. The films deposited at lower powers, which results in lower deposition rates, have compositions similar to that of the target. Heating the substrates during deposition is found to minimise the formation of pinhole defects in films subsequently annealed at higher temperatures. Post annealing leads to a gradual transformation from the as-sputtered amorphous phase to crystalline LAGP thin films. At high annealing temperatures (above 700 °C) both porosity and the GeO2 impurity phase appear in the films and result in lower ionic conductivities. We have optimised the processing conditions to achieve ionic conductivities in excess of 10−4 Scm−1 and activation energies as low as 0.31 eV in films only 1 μm thick, suggesting that LAGP could offer attractive properties as a thin film battery electrolyte material.

Journal Keywords: Solid-electrolyte; Thin films; Sputtering; LAGP

Subject Areas: Materials, Chemistry, Energy

Instruments: I11-High Resolution Powder Diffraction