BIBECHANA 18 (2) (2021) 80-86 80 Morphological analysis of Cu substituted Ni\Zn in Ni-Zn ferrites D. Parajuli 1, 2*, K. Samatha1 1Department of Physics, Andhra University, Visakhapatnam, India 2Department of Physics, Tri-Chandra Multiple Campus, Tribhuvan University, Nepal *Email: deepenparaj@gmail.com Article Information: Received: January 20, 2021 Accepted: May 6, 2021 Keywords: Spinel Ni-Zn ferrite SEM-EDS Critical concentration Nucleation ABSTRACT Cu substituted Ni in Ni0.5-xCuxZn0.5Fe2O4 (x = 0, 0.05, 0.1, 0.15 and 0.2) samples and Cu substituted Zn in Ni0.5Zn0.5−xCuxFe2O4 (x = 0, 0.05, 0.1, 0.15 and 0.2) is synthesized using the sol-gel auto-combustion process. Recently, we have carried out their structural analysis using XRD and FTIR and found a cubic spinel structure. In this paper, we have studied their morphological and compositional structure with the help of a Scanning Electron Microscope (SEM) attached with an Energy Dispersive Spectrometer (EDS). The comparative study shows that the grain size of Cu substituted Ni is greater than Cu substituted Zn in Ni-Zn ferrite. These smaller grain-sized ferrites is preferred for many microstructural applications. Depending on the available magnetic field, sintering temperature, and atmosphere, they can have different nucleation, and hence their application mode is different. They can have a critical concentration that can tune their properties. The EDS attached with the SEM confirmed the proper composition of samples. DOI: https://doi.org/10.3126/bibechana.v18i2.34383 This work is licensed under the Creative Commons CC BY-NC License. https://creativecommons.org/licenses/by-nc/4.0/ 1. Introduction ><< These spinel nanomaterials or ferrites are useful in the fields like microwave devices, ultra-high- density magnetic encoding, coating, etc. [1-3]. They have a crystallographic structure that can bring feasible change in their microstructure and electromagnetic characteristics. If the magnetic properties of those nanomaterials can be controlled then they can be exploited in advanced applications. Most of the spinel ferrite materials have an M2+Fe23+O42- type of structure, where, M is a Transitional Metal Cation. M is on the tetrahedral site and Fe on the octahedral site of the spinel. The study of the shape and material properties of different compositions of the Ni-Cu-Zn ferrite system is increasing these days [4-7]. Magnetic nanoparticles of Cu2+ added nickel-zinc magnetic oxides are commonly utilized in magnetic components for example rotary DY core, transformer, and magnetic inductive core. Similarly, the smaller grains coalesced together forming fine, mailto:deepenparaj@gmail.com https://doi.org/10.3126/bibechana.v18i2.34383 https://creativecommons.org/licenses/by-nc/4.0/ http://nepjol.info/index.php/BIBECHANA D. Parajuli , K. Samatha / BIBECHANA 18 (2) (2021) 80-86 81 larger and non-uniform grains thereby decreasing intergranular porosity on the addition of Cu+2 contents. This property leads them applicable in high-frequency devices [8, 9]. The agglomeration indicates the strong interactions between the particles and grain growth during sintering [10] However, the cadmium substitution on decreases the grain size thereby decreasing dc electrical resistivity. Similarly, the magnetic saturation is decreased indicating the BB interaction i.e. interaction within the B site [11]. Recently, we have carried out the structural analysis using XRD and FTIR of Cu substituted Ni0.5-xCuxZn0.5Fe2O4 (x = 0, 0.05, 0.1, 0.15 and 0.2) samples and Cu substituted Zn in Ni0.5Zn0.5−xCuxFe2O4 (x = 0, 0.05, 0.1, 0.15 and 0.2) and found cubic spinel structure [12]. In the present study, it is planned to formulate nanoparticles of Cu substituted Ni and Cu substituted Zn in Ni-Zn ferrites containing iron oxide as their main components using the sol-gel auto combustion method. The structure and micro- texture of the material with appropriate heat treatment are analyzed. 2. Experimental Techniques and Materials Copper Substituted Nickel-Zinc nanoparticles are prepared by the sol-gel auto-combustion method. 99.99% pure Nickel nitrate, Copper nitrate, Zinc nitrate, Iron nitrate, and citric acid monohydrate with the molecular formula (Ni (NO3)2·6H2O), Cu (No3)3·H2O, (Zn (NO3)2·6H2O), (Fe (NO3)3·9H2O) and (C6H8O7.H2O) respectively, as the starting materials. They are mixed in such a ratio that Ni0.5- xCuxZn0.5Fe2O4 (x = 0.0, 0.05, 0.1, 0.15 and 0.2) samples are prepared. The metal nitrates and citric acid were mixed in a molar ratio of 1:1 and were dissolved in the distilled water to get a clear solution. The solution was made neutral by adding liquid ammonia. The solution was then stirred in a magnetic stirrer maintained at 100oC for 4 hr, decanted, and dried at normal temperature for 40 hr. The flakes thus obtained were combusted and converted into a powder. The powder was sintered in a muffle furnace at 800 °C for 4 h at 5o/min. Similarly, Ni0.5Zn0.5−xCuxFe2O4 (x = 0, 0.05, 0.1, 0.15, and 0.2) are prepared with the same process in sintering temperature 900 °C in the air for 4 h and then followed by a natural cooling to room temperature. The surface morphology studies of all sintered pellets were characterized on a ZEISS scanning electron microscope with accelerating voltage 10 kV available in Analytical Research Laboratory, Andhra University, India. For making pallets, few drops of polyvinyl alcohol were mixed with the powder for shaping them into disc-like pallets after pressing them in a die under the hydraulic press of 5 tons. The pallets were then made as an electrode by sintering them in 800oC in a muffle furnace and polishing their flat sides with gold. 3. Results A. Morphological Study ` i. Morphological of Cu substituted Ni in Ni-Zn ferrite The microstructural images like grain size, pores, inclusions, grain boundaries, particle size, homogeneity, defects, etc. can be obtained with the help of a Scanning Electron microscope. The smaller grain size with low porosity controls the unnecessary spin waves production which is essential for microwave devices. In the same way, the large grain size supports the mobility of the domain wall resulting in high permeability with low coercive value. Similarly, the eddy current losses are checked by the grain boundaries acting as current barriers. The SEM images (from Figure 1(a) to (e)) show that the nickel, copper, and zinc are not miscible and the average size of the grain is ranging from 0.2 to 0.4μm. The grains sizes are nearly equal to in the previous report [13]. ii. Morphological of Cu substituted Zn in Ni- Zn ferrite The microstructural morphological study to investigate the grain size, uniformity, and shape of the Cu substituted Zn in Ni-Zn ferrite sintered at D. Parajuli , K. Samatha / BIBECHANA 18 (2) (2021) 80-86 82 900◦C was also done with the help of a ZEISS scanning electron microscope with accelerating voltage 10 kV as shown in Figure 2 (a-e). The figures show that the grain size is found to increase with copper content up to x=0.15 and then decreases for additional concentration similar to the previous reports [14, 15]. The turning point is called critical concentration. The electric and magnetic properties [16] of nanomaterials are significant for the uniform grain size and boundaries [17] measured by the linear intercept method. From the micrographs, the cupper content has improved the homogeneous spherical grain and low agglomeration similar to the result of Sundararajan et al. [15]. The grain size was found to be in the ranges from 130 to 246 nm with 130 nm for base composition, 183 nm for x=0.20, and the highest average grain size is 246 nm for x=0.15 similar to the previous results [18]. B. Compositional Study: Energy Dispersive Spectroscopy (EDS) Method The elemental composition of the Ni-Zn ferrites was confirmed with the help of EDS and found the presence of O, Fe, Ni, and Zn as shown in Figure 3. 4. Discussion Generally, the single grain is the composition of several crystals. The grain size depends on the sintering temperature and atmosphere [19]. They can be from very small colloidal particles, clay, silt, sand, gravel, cobbles to boulders. SEM study deals with the grain size of the materials which has a significant role in its electric, magnetic, mechanical properties, etc. Further, Ferrite grain size increase with temperature due to higher nucleation and copper content. As an example, ferrite grain size below 2mm transformed to cementite rather than pearlite as being small-sized austenite [20]. To get the size below 1mm, severe plastic deformation (SPD) process can be used which change the plate- shaped pearlite into a spherical cementite particle. This reduction in ferrite grain size from 5 to 1 μm increases the yield strength by 260 MPa. So, grain size reduction enhances the mechanical properties of the material. Further, the larger grain size is best for core loss, magnetic induction, and ac permeability in the weak magnetic field. For the smaller grain size, a larger field is needed for good performance [21]. Moreover, the size reduction produces the quantum confinement effect which we have studied in Metal Oxide Semiconductor especially ZnO and CdO The quantum confinement effects are significant in antibacterial activities. [22-23]. (a) (b) D. Parajuli , K. Samatha / BIBECHANA 18 (2) (2021) 80-86 83 (a) (c) (c) (d) (e) Fig. 1: (a) to (e): FESEM images for of Ni0.5- xCuxZn0.5Fe2O4 (x = 0.0, 0.05, 0.1, 0.15 and 0.2) ferrites (b) D. Parajuli , K. Samatha / BIBECHANA 18 (2) (2021) 80-86 84 (d) (e) Fig. 2: (a-e): SEM micrographs of Ni0.5Zn0.5−xCuxFe2O4 (x = 0, 0.05, 0.1, 0.15 and 0.2) ferrites Fig. 3: EDS counts and elemental weight for Ni0.5Zn0.5Fe2O4 ferrite NPs 5. Conclusions SEM micrograph of Cu substituted Ni in Ni-Zn ferrite reveals the microstructural growth along with heat action and the average size of the grain is ranging from 0.2 to 0.4μm or 200nm to 400nm. Cu substituted Zn in Ni-Zn ferrite makes it easy for sintering thereby improving grain formation, shape, and densification. SEM micrograph shows the increased grain size up to x=0.15 and then decreased for the gradual increase in the concentrations. The turning concentration x= 0.15 is the critical concentration beyond which the size is decreased and agglomeration occurs. The grain size was found to be in the ranges from 130 to 246 nm with 130 nm for base composition, 183 nm for x=0.20, and the highest average grain size is 246 nm for x=0.15. The comparative study shows that the grain size of Cu substituted Ni is greater than Cu substituted Zn in Ni-Zn ferrite. The smaller grain size is preferred for microstructural applications. The EDS attached with the SEM has given the proper composition of samples. The effect of grain size on the electric and magnetic properties will be discussed in the next paper. (e) D. Parajuli , K. 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Contents lists available at ScienceDirect Results in Physics, Results in Physics, 19 (2020) 103508. https://doi.org/10.1016/j.rinp.2020.103508 https://doi.org/10.1016/j.physb.2005.03.010 https://doi.org/10.1088/0022-3727/41/18/185005 https://doi.org/10.1142/S0217984917503183 http://dx.doi.org/10.1155/2015/615739 https://doi.org/10.1371/journal.pone.0001869 https://doi.org/10.1007/BF02833752 https://doi.org/10.1007/s10854-020-05135-3 https://doi.org/10.1016/j.rinp.2020.103508 Copper Substituted Nickel-Zinc nanoparticles are p A.Morphological Study `