Sol-gel route to porous lanthanum cobaltite (LaCoO₃) thin films

Sol-gel-derived LaCoO₃ thin films were deposited on yttria-stabilized zirconia (YSZ) substrates from a lanthanum isopropoxide-cobalt acetate (with 2-methoxyethanol) precursor solution. A chelating agent (2-ethylacetoacetate) and polyethylene glycol (PEG) were used to modify the above-mentioned precursor solution. The La-Co precursor solution was sufficiently viscous, and transparent LaCoO₃ gel films were prepared successfully using a spin-coating technique. Crystallization behavior and microstructure evolution were investigated using X-ray diffractometry (XRD) and scanning electron microscopy (SEM). A single-phase perovskite thin film with the grain size of approximately 50 nm was obtained by heat-treating the spin-coated gel film at a temperature of 600 °C. SEM observations revealed that the microstructure of LaCoO₃ thin films that were prepared from the precursor solution with PEG was porous, and the LaCoO₃ thin film maintained its porous microstructure to a temperature of 800 °C.