Effect of Sintering Temperature on structural, morphological and magnetic properties of Mn0.3Co0.2Zn0.5Fe2O4 Ferrite

In the course of recent years, our society is dealing with extreme issues related to energy storage in small dimensions. However, the development of energy storage systems is lingering behind the fast progression in electrical-powered industries. Convenient electronic gadgets like cell phones, PCs, smartwatches, and so forth request the utilization of energy storage components which has lightweight, flexible, cost-effective, and environmentally friendly in nature [1]. The conventional capacitor and battery have been broadly utilized as energy storage devices inferable from the minimal expense and better execution [2]. Considering the genuine energy demands of recent portable electronic devices, hybrid vehicles, and consumer electronics, an energy storage device such as conventional capacitors and batteries can't satisfy the demands completely. In addition, the conventional capacitors and battery both have their astounding benefits and negative marks. Compared with the batteries, the conventional capacitors have relatively high power densities and low energy density. On the other hand, a battery has a higher energy density and lower power density than a conventional capacitor [3]. With the quick development in the advancement of portable electronics devices, there has been a continually expanding interest for alternative energy storage devices which can bridge the gap between conventional capacitors and battery, and have a high energy density, power density, long cycle life, and fast charge-discharge rates than conventional capacitor and battery. The supercapacitor is a potential alternative means that have higher energy density than a conventional capacitor, higher power density than a battery, fast charge-discharge rates, long cycle, and shelf life [4]. By and by, rather than a battery and conventional capacitors, supercapacitors have been broadly used as portable electronic devices, memory backup systems, hybrid vehicles, and consumer electronics [5]. The electrochemical performance of supercapacitors exceptionally relies upon the active material, substrate, and electrolyte utilized in it.             Ruthenium oxide (RuO2) is one of the best-known electrode materials (active material) which yields a high value of specific capacitance, high electrical conductivity, and reversible charge-discharge properties but there arise some difficulties in the use of ruthenium oxide as an electrode material because it is highly toxic and too much expensive [6]. These above difficulties can be developed by the use of the potential candidate spinel ferrite (MFe2O4, M = Fe, Co, Ni, Cu, Mn, Zn, etc.) material/doped spinel ferrite (active material) for superior electrochemical activity as compared to single metal oxide because of the large scale production, low cost, flexibility in the structure and morphology, and eco-friendly nature. However, increasing supercapacitor performance is very much challenging.             As compared with the literature in this field, there is no result on the synthesis and effect of sintering temperature on the structural, morphological, magnetic, and electrochemical properties of Mn0.3Co0.2Zn0.5Fe2O4 ferrite nanoparticles.             In the present study, our main objective is to synthesize Mn0.3Co0.2Zn0.5Fe2O4 ferrite nanoparticles at different sintering temperatures (750, 950, and 1150 OC) with a simple sol-gel technique Fig. 1 involving less energy and low-cost metallic salt as raw materials. Various characterization techniques viz. XRD, FTIR, FESEM, EDX, and VSM were performed for investigating the structural, morphological, and magnetic properties of the ferrite nanoparticles. Taking in view of these above results the electrochemical properties can be further studied for energy storage applications.  Fig. 1. Sol-gel auto combustion method for synthesis of Mn0.3Co0.2Zn0.5Fe2O4 ferrite nanoparticles at different sintering temperatures (750, 950, and 1150 OC).               From all the synthesized samples the single-phase spinel structure with cubic symmetry (Fd-3m space group) was observed for the sample sintered at 1150 OC which was assured by the XRD studies as shown in Fig. 2. The crystallite sizes estimated utilizing Scherrer's formula affirms the nanocrystalline nature of the incorporated samples as reported in Table 1. Fig. 2. X-ray diffraction pattern of Mn0.3Co0.2Zn0.5Fe2O4 samples. Table 1. The interlayer spacing (d), lattice constant (a0), unit cell volume (V), and crystallite size (D) of Mn0.3Co0.2Zn0.5Fe2O4 samples. Sintering Temperature ( OC ) d (A) a0  (A) V (A)3 D (nm) 750 2.544 8.437 600.70 18.1 950 2.545 8.440 601.25 29.3 1050 2.549 8.454 604.23 50.2             FTIR spectra shown in Fig. 3 affirm the formation of spinel structure at 1150 0C by the appearance of characteristic vibrational bands near 400 and 600 cm-1 which corresponds to the octahedral or B-site and tetrahedral or A-site respectively [7]. Fig. 3. FTIR spectra of Mn0.3Co0.2Zn0.5Fe2O4 samples.             FESEM micrograph measures particle size (average) in the nanoscale range by using ImageJ software and reveals the presence of grains that were agglomerated and having porous morphology as presented in Fig. 4. Fig. 4. FESEM micrograph and particle size histogram of Mn0.3Co0.2Zn0.5Fe2O4 sample.               The stoichiometric proportions of the synthesized sample were confirmed by the EDX spectra as shown by Fig. 5. Fig. 5. EDX spectra of Mn0.3Co0.2Zn0.5Fe2O4 sample at 1150 OC.               The M-H curve of the incorporated sample (Fig. 6) shows an S-shaped hysteresis curve which reveals characteristics similar to that of the ferromagnetic material [8]. VSM study reveals the increment in the saturation magnetization with the increase in the sintering temperature. The magnetic soft nature of the incorporated samples due to the low coercivity makes them suitable for electromagnetic radiation material [9] and power application [10]. The squareness ratio for all the synthesized samples was found to be less than 0.5 which reveals the interaction of nanoparticles by magnetostatic interactions [11]. Fig. 6. M-H curve of Mn0.3Co0.2Zn0.5Fe2O4 sample.