New water-based sol-gel synthesis routes for LaNi0.6Fe0.4O3-δ thin films

Two synthesis routes for approximately 100 nm thick layers of LaNi0.6Fe0.4O3-δ (LNF64) are presented. Aqueous solutions of acetate or nitrate-precursors were deposited on Ce0.9Gd0.1O2-δ substrates by spin coating. After thermal annealing at 700 °C for 3 h, the thin films were characterized by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. The DC electrical conductivity of the LNF64 thin films was determined by four-point van der Pauw measurements as a function of temperature (20 ≤ T/°C ≤ 400) at 1 × 10− 3 ≤ pO2/bar ≤ 1. At the surface and cross section a nanocrystalline microstructure with grain sizes of approximately 50-100 nm was observed. The DC electrical conductivity of the thin films increases with increasing temperature and increasing pO2. A maximum electrical conductivity of 320 S/cm was found at 400 °C and pO2 = 1 bar which agrees with the literature data for LNF64 bulk samples.