RESUMO
Pristine and Dy substituted MnFe2O4,MnFe2-xDyxO4(x= 0.00, 0.02, 0.04, 0.06, 0.08 & 0.10) were successfully synthesized by sol-gel method to investigate the dielectric properties of the system. MnFe2O4exhibits a high dielectric permittivity of order 104which is further augmented by 60% through Dy substitution. This is owing to the rise in interfacial polarization resulting from localized states, dipolar polarization arising from the multiple valence states of Fe and Mn ions, atomic polarization due to structural distortion induced by strain, and electronic polarization stemming from the concentration of free charge carriers. The enhancement of induced strain, mixed valence ratio of Fe2+/Fe3+and Mn4+/Mn2+, localized states, and free charge carrier concentration are confirmed from the XRD, XPS, and optical studies, respectively. The dielectric relaxation mechanism of MnFe2-xDyxO4follows a modified Havriliak-Negami relaxation model with conductivity contribution. Complex impedance analyses further validate the contribution of grain-grain boundary mechanisms to the dielectric properties confirmed through Nyquist plots. A comprehensive analysis of conductivity reveals the significant impact of Dy substitution on the electrical conductivity of MnFe2O4. This influence is strongly related to the variations in the concentration of free charge carriers within the MnFe2-xDyxO4system. The understanding of the underlying physics governing the dielectric properties of Dy-substituted MnFe2O4not only enhances the fundamental knowledge of material behavior but also opens new avenues for the design and optimization of advanced electronic and communication devices.
RESUMO
Polycrystalline GdFe1-xNixO3(x = 0.00, 0.02, 0.04) samples was synthesised using a glycine assisted sol-gel method to investigate the enhanced magnetic and electric properties of Ni substituted GdFeO3systems. TG-DSC analysis of prepared samples confirms that GdFe1-xNixO3have good thermal stability in high temperatures. The system has been stabilized in an orthorhombic structure with space group Pbnm.The elemental composition of GdFe1-xNixO3has been estimated from EDAX spectrum. The results showed oxygen deficiency on increasing the Ni substitution and it has been supported by Rietveld refinement. FE-SEM images and Brunauer-Emmett-Teller analysis reveals that GdFe1-xNixO3is a highly porous material and its porosity and specific area increases with Ni substitution. Magnetic measurements indicates that the system exhibited ferrimagnetic behaviour at low temperatures and canted antiferromagnetic behaviour at room temperature. Forx = 0.04 Ni content, magnetization reversal for applied field of 25 Oe has been observed. Increased coercivity of GdFeO3with Ni substitution has been attributed to the grain size effect. From electrical point of view, dielectric permittivity of GdFeO3has been enhanced with Ni substitution. This enhancement has been attributed to the cumulative effects of hopping of Fe2+-Fe3+ions, grain-grain boundary contribution, and space charge polarization. The role of grain-grain boundary contribution is evident from electric modulus spectrum. The space charge effect has been realized in both impedance spectrum and dielectric loss. Temperature-dependent dielectric studies were conducted to understand the mechanisms and various aspects that contribute to the dielectric enhancement. A highly lossy capacitive nature in theP-Eloop also suggests space charge effects due to Ni substitution in Fe sites. Availability of free charge carrier concentration is correlated with the optical properties of GdFe1-xNixO3. The decrease of optical band gap (2.5-2.21 eV) on increasing Ni content suggests the increasing electronic contribution in the system.