A novel, simple, and feasible route for synthesizing air-stable, water-soluble tantalum precursors has been developed using moisture-insensitive Ta2O5 as a starting source of the Ta element, based on the conventional basic flux method. Various analytical techniques have been used to characterize the formation mechanism, purity, and thermal decomposition features of these Ta precursors including tantalum oxalate, tantalum peroxo-tartarate, and tantalum peroxo-citrate. These Ta precursor solutions have a higher Ta ion purity over 99.0 wt% and a lone shelf life. Using home-made Ta precursors, photocatalyst powders of 1 mol% Ta-doped ZnO and ferroelectric films of SrBi2Ta2O9 on Pt/TiO2/SiO2/Si substrates have been prepared by a modified polymerizable complex (PC) route. Ta-doped ZnO powders from polymeric precursors show hexagonal wurtzite structures with uniform smaller grain sizes of 25 nm and a larger specific surface area of 32 m(2)/g. Moreover, they exhibit excellent photocatalytical activity under visible light irradiation compared with pure ZnO powders. PC-derived SrBi2Ta2O9 films also show comparable ferroelectric and dielectric properties with those from the metalorganic decomposition method. All these qualities indicate that water-soluble Ta precursors are potential and competitive candidates for photocatalyst and ferroelectric applications.