TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The method (I) further comprises: precipitating an aluminum salt, where precipitating comprises evaporating sufficient water to cause the aluminum salt to precipitate; isolating the aluminum salt; washing isolated aluminum salt with a solvent sufficiently polar to selectively remove zinc-containing reaction products; redissolving isolated aluminum salt in water to form a homogenous solution; and adding additional nitrate to adjust the nitrate-to-aluminum ratio to obtain a substantially continuous and substantially smooth film when coating precursor solution is used to form a thin film. In the method, the step of forming a layer of precursor coating material comprises spin coating, spray coating, dip coating, knife edge coating or aerosol chemical vapor deposition. In method (III): the coating is a passivation coating or an optical coating. Preferred Components: The aqueous inorganic precursor composition has: an aluminum cation concentration of 0.01-3.5 M; and a polyatomic anion concentration of 0.1-2.5 times the aluminum cation concentration. The metal is zinc, aluminum, iron and/or copper. The layer of precursor coating material has an average thickness of 0.5-750 nm. The dielectric coating film limits electron-hole recombination rates in silicon. The dielectric aluminum oxide film has a refractive index between 1.45-1.65. The dielectric aluminum oxide film functions as an anti-reflection coating film and as an internal-reflection coating film. The dielectric film has: breakdown strength of greater than 1 MV/cm; and a relative dielectric constant of at least 5.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The solvent is an alcohol and/or ester, where the alcohol or ester has less than or equal to 10 carbon atoms comprising methanol, ethanol, propanol, isopropanol, ethyl ethanoate, methyl ethanoate, ethyl propanoate and/or methyl propanoate. EXAMPLE - Aluminum nitrate nonahydrate (Al(NO3)3.9H2O) powder was dissolved in water to make a aqueous aluminum (1.6 M) solution. Zinc power was then added to the solution to obtain a total metal concentration of 2.4 M (zinc: aluminum = 1:2). The solution was stirred mildly with a magnetic stir bar under atmospheric conditions, to obtain a clear solution after stirring for 5 hours. The solution was kept in an uncovered crystallizing dish in the fume cupboard for evaporation (-30 ml in 3 day). A polycrystalline powder was subsequently isolated. The polycrystalline powder was washed four times with isopropyl alcohol to remove zinc nitrate. The aluminum complex hydrate of formula ((Al13(OH)24(H2O)24(NO3)15) was separated from other reaction products (e.g. zinc nitrate and excess aluminum nitrate). The resultant powder was kept in ambient environment for 5 hours to obtain aluminum hydrate powder of formula ((Al1 -3(OH)24(H2O)24) (NO3)15.NH2O). The obtained aluminum hydrate powder was dissolved with aluminum nitrate nonahydrate (1:3-2:3), to obtain solution precursor for thin-film fabrication.