Samarium substituted M-type Sr hexaferrites: The structural, magnetic and electrochemical properties for supercapacitor applications.

In the current project the samarium substituted strontium hexaferrites with general formula SrSm x Fe 12-x O 19 (where x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5) nanocrystalline powder have been successfully synthesized employing sol-gel auto-combustion route. The fabricated samples have been sintered at 1200 °C for 2 h. The structural, functional group, morphological, elemental, optical, magnetic, dielectric and electrochemical properties have been studied by X-Ray diffractometer, Fourier transformer infrared spectroscopy, scanning electron microscopy, Energy dispersive X-Ray, UV–visible, vibrating sample magnetometer, Inductor capacitor and resistor meter and cyclic voltammetry, galvanostatic charging discharging respectively. The structural analysis confirms the formation of the single-phase Magnetoplumbite structure of all the samples. The crystallite size decreases with increasing Sm+3 ions concentration. The characteristic bands of hexagonal structure present in the range of 400–660 cm−1 which correspond to metal–oxygen (M − O) stretching and vibrational bonds. The bandgap increases from 4.21 to 4.86 eV. The magnetic properties reveal the clear ferromagnetic M − H curve in which the value of coercivity increases and saturation magnetization decreases. The dielectric constant and tangential loss of the material both decrease with increasing frequency. Conversely, the ac conductivity of the material increases with increasing applied frequency. This is the natural behavior of ferrites. This behavior can be attributed to the polarization and orientation of the dipoles within the material in response to the applied electric field. The observed increase in σ at higher frequencies suggests that the material may be useful in applications where high-frequency electrical properties are desired such as in the development of high-speed electronic devices. The specific capacitance increases monotonically up to 1020 F g −1 with increasing Sm+3 concentration. The samarium substituted hexaferrites are recommended to fabricate the high energy density charge storage devices such as supercapacitors. [ABSTRACT FROM AUTHOR]