Structural and dielectric properties of A(Fe1/2Ta1/2)O3 [A=Ba, Sr, Ca]

Abstract The complex perovskite oxide barium iron tantalate (BFT), BaFe 1/2 Ta 1/2 O 3 , strontium iron tantalate (SFT), SrFe 1/2 Ta 1/2 O 3 and calcium iron tantalate (CFT), CaFe 1/2 Ta 1/2 O 3 are synthesized by a solid-state reaction technique. Rietveld refinement of the X-ray diffraction data of the samples shows that BFT and SFT crystallize in cubic structure, with lattice parameter a = 4.06 A for BFT and 3.959 A for SFT, whereas CFT crystallizes in orthorhombic structure having lattice parameters a = 5.443 A, b = 5.542 A and c = 7.757 A. 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.