The complex perovskite oxide barium iron tantalate (BFT), BaFe1/2Ta1/2O3. strontium iron tantalate (SFT). SrFe1/2Ta1/2O3 and calcium iron tantalate (CFT). CaFe1/2Ta1/2O3 are synthesized by a solid-state reaction technique. Rietveld refinement of the X-ray diffraction data of the samples shows that BET and SFT crystallize in cubic structure, with lattice parameter a = 4.06 angstrom for BFT and 3.959 angstrom for SFT, whereas CFT crystallizes in orthorhombic structure having lattice parameters a = 5.443 angstrom, b = 5.542 angstrom and c = 7.757 angstrom. Fourier transform infrared spectra show two primary phonon modes of the samples at around 450 cm(-1) and 620 cm(-1). The compounds show significant frequency dispersion in its dielectric properties. The complex impedance plane plots of the samples show that the relaxation (conduction) mechanism in these materials is purely a bulk effect arising from the semiconductive grains. The relaxation mechanism of the samples is modelled by Cole-Cole equation. The frequency dependent conductivity spectra are found to follow the power law. (C) 2011 Elsevier Ltd. All rights reserved.