The aim of the present work is to investigate newly sintered ceramics of gadolinium-substituted Aurivillius-type bismuth titanate, Bi2.5Gd1.5Ti3O12, by the impedance spectroscopy. The measurements were performed as a function of both frequency and temperature in the frequency range 20 Hz-1 MHz and in the temperature range 300 K-1050 K. The electrical conductivity and dielectric relaxation have been analyzed in terms of specific resistivity and electrical modulus. The onset of the ionic conductivity in the ceramic appears above the phase transition temperature, T-0 = 468 K. Activation energy for the conductivity was found to be Delta E-A = 0.98 eV, while conductivity in grains has Delta E-g = 0.93 eV. (C) 2010 Elsevier B.V. All rights reserved.