Amorphous barium titanate (a-BaTiO3) thin films were deposited by the RF magnetron sputtering technique. The films were grown directly on copper substrates which were maintained at low temperature during deposition (water-cooled substrates). We studied the permittivity (dielectric constant and loss) in the 0.1 Hz-100 kHz range, from -100 to 225 degrees C. Leakage currents (DC conductivity) were also studied as a function of the applied field and temperature. At room temperature the dielectric constant is 18.5 (100 kHz), the dissipation factor is 4 x 10(-3) and the conductivity is 6 x 10(-16) S/cm (2.7 mu m thick films). A dielectric dispersion is observed at low frequencies that becomes pronounced when the temperature is increased. (c) 2005 Elsevier B.V. All rights reserved.