The formation of ferroelectric BaBi2Ta2O9 (BBT) by a sol–gel process was studied by X-ray, Raman and infrared (IR) spectroscopy. Our results show that the formation of a Bi-layered phase proceeds via an intermediate fluorite-type phase. This method allows obtaining a BBT phase already at 750 °C. This temperature is about 150–200 °C lower than that required in the conventional solid-state reaction. Therefore, a material with smaller particle size can be obtained. Raman and IR studies of the obtained Bi-layered phase show that phonon properties of the synthesized particles are slightly different from those of the bulk material due to the size effect, defects and weak changes in local order. Temperature dependence of Raman and IR wavenumbers is consistent with the orthorhombic distortion of the BBT structure. Copyright © 2011 John Wiley & Sons, Ltd.