A method for preparing nanocrystalline ceramic thin films, particularly at low firing temperatures <1000.degree. C. The method for preparing ceramic thin films comprises preparing a seed gel of metal oxide, dissolving a source compound for cations of the oxide's metal constituents in the solution, then adding a polymerizable organic solvent to the solution and heating to form a polymeric precursor having uniformly dispersed gel seeds within a solid gel structure whereby any voids within the structure are filled with metal cation-containing polymeric precursor. The polymeric precursor is free of precipitates. A surface of a substrate is then coated with at least one layer of the gel-seeded polymeric precursor to form a uniform film of gel-seeded polymeric precursor wherein the film has a thickness of 100 nm to 200 nm per layer. The film is then sintered to convert the film to a nanocrystalline ceramic thin film having a thickness of 100 nm to 1 .mu.m and being substantially free of defects.
 The invention was made with government support under contract no. DE-AC05-00OR22725 awarded by the United States Department of Energy to UT-Battelle, LLC., and the government has certain rights in the invention.