Interlayer for solid oxide cell

A method of forming an interlayer of a solid oxide cell unit on the surface of a substrate may include: providing a base interlayer solution comprising a solution of a soluble salt precursor of a metal oxide (crystalline) ceramic and crystalline nanoparticles, depositing the base interlayer solution onto the surface of the substrate, drying the base interlayer solution to define a nanocomposite sub-layer of the soluble salt precursor and nanoparticles, heating the sub-layer to decompose it and form a film of metal oxide comprising nanoparticles on the surface, and firing the substrate with the film on the metal surface, to form a nanocomposite crystalline layer.