Synthesis, structural and optical properties of perovskites-type: Sr3Fe2+xMo1-xO9-3x/2 (x=0.30, 0.45, 0.60, 0.75 and 1.00)

Perovskite-type oxides Sr3Fe2+xMo1-xO9-3x/2 (x = 0.30, 0.45, 0.60 0.75, and 1.00) were synthesized in the polycrystalline form using a solid-state reaction route in the air. These materials have been studied at room temperature using the techniques of XRD, Mossbauer and UV-visible spectroscopies. The crystal structures were resolved by the Rietveld refinement method and revealed that this series adopts two phase transitions from a tetragonal I4/mcm phase (x = 0.30, 0.45 and 0.60) to a simple cubic Pm-3 m phase (x = 0.75), to another tetragonal P4/mmm phase (x = 1.00). The values of the isomer shift (IS) and quadrupole splitting (QS) confirm that the formal oxidation state of the iron contained in our compounds consist of mixed valence Fe3+ and Fe4+ cations for the octahedral environment. The M?ssbauer spectrum of the SrFe0.917Mo0.083O3-delta (x = 0.75) sample is consistent with the iron atom in a cubic lattice site. The direct band gap energy increases from 1.70 to 2.25 eV with increasing Fe content. Plots of optical parameters, such as absorption coefficient, refractive index, extinction coefficient, optical conductivity, real and imaginary parts of the dielectric function, electric modulus and complex impedance, were achieved in the photon energy range 1.54-4.94 eV by means of UV?vis spectrophotometry experiments. (C) 2021 Elsevier Ltd. All rights reserved.