Investigation of alteration in physical properties of dysprosium orthochromite instigated through cobalt doping

Abstract

Abstract We report the systematic investigations on DyCr1–xCoxO3 (0 ≤ x ≤ 0.3) samples prepared through sol-gel auto combustion process. Rietveld refinement of the powder x-ray diffraction patterns assures the formation of mono-phase orthorhombic structure with space group Pbnm. In order to get an obvious view about the effect of substitution of Cr3+ with Co3+ ions on crystallographic parameters of these samples, the tilt angles, cell and orthorhombic distortions were calculated. The average crystallite sizes and lattice strain as computed from the Williamson-Hall analysis are found to rise with the increase in Co content. The porosity of the synthesized samples lies in between ∼30 and 38%. The Fourier transform infrared (FTIR) spectra of these samples affirm the formation of desired crystal structure. Field emission scanning electron microscopy (FESEM) images exhibit the existence of polycrystalline microstructure. The energy dispersive x-ray (EDX) analysis assures the elemental compositions of the prepared samples. UV/Visible spectroscopy is utilized to estimate the energy band gap, Urbach energy and threshold wavelength. The energy band gap reduces whereas Urbach energy and threshold wavelength enhance on increasing the cobalt content. Dielectric responses of these samples have been analysed in view of “universal dielectric response” model. AC conductivity increases with the increase in frequency and that affirm the small polaron hopping type of conduction mechanism in the investigated frequency range. The relaxation peaks appear in imaginary part of impedance spectra shift toward lower frequencies with the increase in Co concentration which indicates the higher values of relaxation time in the doped samples. Differential thermal analysis reveals the structural transitions and improved thermal stability of the Co doped samples.