Synthesis, Structural and Magnetic Characterization of Superparamagnetic Ni0.3Zn0.7Cr2−xFexO4 Oxides Obtained by Sol-Gel Method

Abstract

The sol-gel process was used to produce ferrite Ni0.3Zn0.7Cr2−xFexO4 compounds with x = 0, 0.4, and 1.6, which were then subsequently calcined at several temperatures up to 1448 K for 48 h in an air atmosphere. X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), and 57Fe Mössbauer spectrometry were used to examine the structure and magnetic characteristics of the produced nanoparticles. A single-phase pure Ni0.3Zn0.7Cr2−xFexO4 nanoparticle had formed. The cubic Fd3¯m spinel structure contained indexes for all diffraction peaks. The crystallite size is a perfect fit for a value of 165 ± 8 nm. Based on the Rietveld analysis and the VSM measurements, the low magnetization Ms of Ni0.3Zn0.7Cr2−xFexO4 samples was explained by the absence of ferromagnetic Ni2+ ions and the occupancy of Zn2+ ions with no magnetic moments in all tetrahedral locations. Moreover, because of the weak interactions between Fe3+ ions in the octahedral locations, the magnetization of the current nanocrystals is low or nonexistent. According to Mössbauer analyses, the complicated hyperfine structures are consistent with a number of different chemical atomic neighbors, such as Ni2+, Zn2+, Cr3+, and Fe3+ species that have various magnetic moments. A Fe-rich neighbor is known to have the highest values of the hyperfine field at Fe sites, while Ni- and Cr-rich neighbors are responsible for the intermediate values and Zn-rich neighbors are responsible for the quadrupolar component.

Optical, Dielectric, and Electrical Properties of Tungsten-Based Materials with the Formula Li(2−x)NaxWO4 (x = 0, 0.5, and 1.5)

“…Each diffractogram shows the following: the experimental points (black circles), the calculated curve (red line), the difference between the experimental and calculated profiles (blue line), and the Bragg positions (green line). We have been careful to follow the known sequence of steps in order to release different crystallographic parameters during the structural refining process of the three samples[36]. This confirms the refinement's stability when all the parameters become available.…”

“…The SEM images clearly show that the three compounds have a compact structu with just a few pores and a tendency for clustering together because of the humid en ronment that lithium creates. Also, these images demonstrate a homogeneous distribut of grains with sizes around 5 [36], 2.6, and 4 µm [35] for the three compositio Li0.5Na1.5WO4, Li1.5Na0.5WO4, and Li2WO4, respectively.…”

“…In fact, Figure 7a,b and Figure 8a,b show the temperature dependence of the relative dielectric constant with a fixed frequency for the compounds Li0.5Na1.5WO4 and Li1.5Na0.5WO4 [34], respectively. [36,38].…”

“…Figure 6. Differential scanning calorimetric of (a) Li 1.5 Na 0.5 WO 4 and (b) Li 0.5 Na 1.5 WO 4[36,38].…”