To obtain beta-phase dominant ferroelectric poly(vinylidene fluoride) (PVDF) homopolymer thin films on aluminum-coated silicon substrates, the retaining and loss of water were manipulated by introducing several hydrated and hygroscopic chemicals in the precursor solutions, including aluminum nitrate nonahydrate, aluminum chloride hexahydrate, chromium nitrate nonahydrate, tetra-n-butylammonium chloride, and one hygroscopic but nonhydrated chemical, ammonium acetate. Their ability of retaining water during the thermal annealing of the films and the relationship between water retaining and the effects on promoting the beta phase were investigated. The results showed an ideal scenario was that the added hydrated salts should be able to retain substantial amount of water during the PVDF crystallization to effectively promote the beta phase but completely dehydrate or decompose at the further elevated annealing temperature in order to obtain beta-phase dominant PVDF film without substantially incorporating water and deteriorating the electrical properties. As one of the hydrated chemicals well satisfying the above requirements, Al(NO3)(3)center dot 9H(2)O, of different amounts was introduced to the PVDF precursor solutions and the optimal resulting beta-phase dominant ferroelectric PVDF thin films exhibited smooth morphology, low dielectric loss, high remnant polarization of 89 mC/m(2), and large effective piezoelectric coefficient d(33) of -14.5 pm/V (under the clamping of the substrate). (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2410-2418, 2009