Spin Coating of a Ca(Ti,Fe)O3 Dense Film on a Porous Substrate for Electrochemical Permeation of Oxygen

A dense Ca(Ti_0.75Fe_0.25)O_3−α (Ca(Ti,Fe)O₃) film, which is a mixed conductor of oxide ions and electrons/holes, was prepared on a porous CaTiO₃ substrate by a spin-coating method. The calcined Ca(Ti,Fe)O₃ powder with 2–3 μm grain sizes was mixed with a dispersant in ethanol to form the slurry for spin coating. A uniform Ca(Ti,Fe)O₃ green film was obtained at 1000–1500 rpm on the rotating porous CaTiO₃ substrate, which had an average pore diameter of a few micrometers. The optimum sintering conditions for the spin-coated films were a soaking temperature of 1235°C and a holding time of 2 h, in air. A dense, sintered Ca(Ti,Fe)O₃ film }20–50 μm thick was prepared by repeating the coatingsintering process. The gas-tight film prepared on the porous substrate exhibited higher electrochemical permeation of oxygen at an operating temperature of 1000°C compared with that of thicker, sintered Ca(Ti,Fe)O₃ disks.