Aqueous peroxotitanium acid solution derived from the TiO2 fluorinated using F-2 gas was used for the preparation of nano-sized BaTiO3 particles in this study. The prepared aqueous peroxotitanium acid solution having a homogeneous pale yellow-green was very stable even for 1 year. Nano-sized BaTiO3 particles were synthesized under different pH values (3-8) by a reaction between the prepared peroxotitanium acid and the Ba(OH)(2) through a co-precipitation method. Depending on pH values, the prepared BaTiO3 particles had two kinds of phases; ferroelectric phase (tetragonal, pH 3-7) and para-electric phase (cubic, pH 8). Namely, with increasing the pH values, average particle sizes of BaTiO3 were decreased from 300 nm to 40 nm and it affected a dielectric constant of BaTiO3. The dielectric constant (4200) of BaTiO3 with 75 nm prepared using the peroxotitanium acid solution was 3 times higher than that with 300 nm of BaTiO3. (C) 2014 Elsevier B.V. All rights reserved.