Structure, Mössbauer, electrical, and γ-ray attenuation-properties of magnesium zinc ferrite synthesized co-precipitation method

For technical and radioprotection causes, it has become essential to find new trends of smart materials which used as protection from ionizing radiation. To overcome the undesirable properties in lead aprons and provide the proper or better shielding properties against ionizing radiation, the tendency is now going to use ferrite as a shielding material. The co-precipitation method was utilized to prevent any foreign phases in the investigated MZN nano-ferrite. X-ray diffraction (XRD) and Fourier transmission infrared spectroscopy (FTIR) methods were used to analyze the manufactured sample. As proven by XRD and FTIR, the studied materials have their unique spinel phase with cubic structure Fd3m space group. The DC resistivity of Mg–Zn ferrite was carried out in the temperature range (77–295 K), and its dependence on temperature indicates that there are different charge transport mechanisms. The Mössbauer spectra analysis confirmed that the ferrimagnetic to superparamagnetic phase transition behaviour depends on Zn concentration. The incorporation of Zn to MZF enhanced the nano-ferrite density, whereas the addition of different Zn-oxides reduced the density for nano-ferrite samples. This variation in density changed the radiation shielding results. The sample containing high Zn (MZF-0.5) gives us better results in radiation shielding properties at low gamma, so this sample is superior in shielding results for charged particles at low energy. Finally, the possibility to use MZN nano-ferrite with various content in different ionizing radiation shielding fields can be concluded.


Materials and methods
In the presence investigation of Mg (1−x) Zn x Fe 2 O 4 samples where (x = 0.0, 0.10, 0.20, 0.30, 0.40 and 0.50) ferrite system were prepared using the Co-precipitation method 29,30 . The starting materials were MgCl 2 ·6H 2 O, ZnCl 2 , and FeCL 3 ·6H 2 O (1:2 molar-ratio) by addition 25% amonia-solution. The whole substance utilized was brought in from Oxford Lab and was of very high chemical purity (99.99%). Reagent. The ferrite system was prepared in a typical reaction, The volume of the reaction mixture was combined under magnetic stirring during a continual gradual addition of 25 ml to a 25% ammonia solution, with the heating continuing for thirty minutes. A black precipitate was decanted and washed with 500 ml distilled water in a changing magnetic field (Scheme 1).
The linear attenuation coefficients (µ) of ferrite samples have been measured experimentally using the narrow beam method in conjunction with a Pb-collimator. The collimated photons, which have varying energy, have interacted with several types of glass samples. Radiation measurements were performed with a NaI (Tl)scintillation detector (Oxford model) with a 3-3-in. detection window, which was coupled to a multichannel analyzer 31 . The radioactive sources that were employed in the experiment were Ba-133 (81 and 356 keV, 1 µCi), Cs-137 (662 keV, 5 µCi), Co-60 (1173 and 1332 keV, 10 µCi), and Th-233 (911 and 2614 keV, 20 µCi). Figure 1 depicts the experimental setup, which includes the source, sample, and detector. The area beneath photopeak has been used to determine the photon intensity without and with absorber for each gamma-line in the experiment. The uncertainties were fewer than 1% of the total number of uncertainties. The spectra were analyzed utilize the Genie-2000 software, which was developed by Canberra.
The structural and lattice parameter of Mg (1−x) Zn x Fe 2 O 4 samples were determined based on the full width at half maximum-FWHM (β), Bragg angle (θ in radians), and Miller indices of each plane (h k l) of the diffraction peak. With the help of the following equations, we can determine the interplanar distance (d′), microstrain (ɛ), interchain separation (R), the crystallite size (d), dislocation density (δ), and distortion parameters (g) 36 :     37 . This decrease can be attributed to replacing Mg 2+ ion with a smaller ionic radius (0.066 nm) with Zn 2+ ion with a larger ionic radius (0.082 nm). Also, the unusual density behavior that grows up to x = 0.3 and then decreases may be attributed to the replacement of lighter Mg by heavier Zn atoms and the distribution of zinc concentration among sublattice and, therefore, the influence of condensation on the crystal structure 38 . The assessed values in Table 1 show that the Mg-Zn ferrite composition significantly reduces both XRD and bulk density. This is related to the replacement of Mg 2+ ion with lower ionic radius (0.066 nm) by Zn 2+ ion with a larger ionic radius (0.082 nm) Zn 2+ ions in a spinel ferrite, on the other hand, have a significant affinity for tetrahedral interstitial spaces (A-sites) and may therefore replace both Mg 2+ and Fe 3+ ions in A-sites as given from The cation distribution. All of this demonstrates that the proportion of vacancies in the materials is increasing, which has an impact on packing density. Figure 4 illustrates the FTIR spectra in the wavenumber range (400-1500 cm −1 ) at room temperature for Mg (1−x) Zn x Fe 2 O 4 samples prepared using the co-precipitation method. It can notice that the higher frequency  The force constants (FC) at the A and B-sites, which are dependent on the vibrational frequencies, are (F Octa ), and (F Tetra ), respectively, as given in Table 2. It can be seen that the force constant at the tetrahedral site is more extensive than that at the octahedral sites. The reduction in the force constant at the tetrahedral site after Zn 2+ substitution in MgFe 2 O 4 indicates that Zn 2+ ions occupy the tetrahedral sites. F = 4πc 2 v 2 µ was used to calculate the force constant of vibrating bonds, where c is the speed of light in space (cm/s), is the wavenumber of frequency, and is the decreased mass of Fe 3+ and O 2− ions, which is given by µ = m o * m Fe m o +m Fe

.
It can show from Fig. 5 that there is an overlapping in the absorption band in FTIR spectra for all samples. Therefore, for more analysis and getting profound information about the changes in the structure and position of the absorption band which occur through the investigated samples by using means of the deconvoluted spectra via several Gaussians peaks ≈ (8-14 peaks). All the getting parameters which getting from FTIR deconvoluted peaks are illustrated in Table 3. Figure 6a,b show the dependence of electrical resistivity and conductivity for Mg (1−x) Zn x Fe 2 O 4 ferrite system upon temperature ranges (77-295 K). It can clearly be noticed that the existence of two linear regions characterizes each conductivity curve which, can be attributed to the presence of different charge transport mechanisms 41,42 . The ln(σ) versus 1000/T plot shows a mono-linearity relationship to estimate the activation energy across the entire temperature range. Therefore, the activation energy (E a ) was determined using the Arrhenius equation where the corresponding ln(σT) against 1000/T plot shows an approximately linear relationship as shown in Eq. (9) [43][44][45] .

Electrical properties.
In this equation, ρ o is the resistivity at room temperature, E is the activation energy in electron volts, k is the Boltzmann's constant, 8.625 × l0 -5 eV/K, and T is the absolute temperature. There were two parallel conductivity processes with differing activation energies that were responsible for the change in slope in all curves. This shift in slope is often seen at temperatures that are close to the Curie temperature of the samples (Tc) [46][47][48] .
It was possible to compute the activation-energy of each sample within the observed temperature range at the slope of linear plots of resistivity. According to the results, the activation energy was determined to be ranged 0.21-0.76 eV, as shown in Table 4 and Fig. 7. It was discovered that increasing the Zn content in the system Mg (1−x) Zn x Fe 2 O 4 ferrite up to x = 0.2 resulted in an increase in activation energy, and then decreases can be attributed to the theory of can be attributed to the presence of different charge transport mechanisms and the decrease this can be attributed to the theory of a change in activation energy is due to the splitting of the conduction band and the valence bands below (Tc) the higher value of activation energy at higher concentration of Zn indicate the strong blocking of the conduction mechanism between Fe 3+ and Fe 2+ ions 48 .
Mösbauer spectroscopy. For all samples weighing 0.015 g, homogenous and well milled Mössbauer spectroscopy measurements were performed. The sequential decay of the 57 Co source produced 14.4 keV rays (5 mCi). All measurements were performed over a speed range of ± 10 mm s at room temperature (RT), and spectral data were fitted using Lorentzian line shapes. The Mösbauer spectra of Mg 1−x Zn x Fe 2 O 4 were acquired at (RT) and fitted using were fitted using Lorentzian line shapes (Fig. 8). Illustrated the hyperfine parameters, isomer shift (I.S.), magnetic hyperfine field (Hhf), quadrupole shift (Q.S.), relative area (A0), and line width (Г). Analyzing the Mösbauer spectra for all recorded spectra (x = 0-0.5) is characteristic by splitting doublets, which attributed to the presence of Fe 3+ ion at the tetrahedral and octahedral site and confirmed the superparamagnetic behavior of the Mg-Zn ferrite samples 49,50 .
A single sextet (B) in addition to superparamagnetic doublet were observed; this indicates relaxation effects, i.e., the presence of ions only in the octahedral B site whereas the magnetic sextet of A site vanishes. However, The fitted parameters given in (Table 5)  www.nature.com/scientificreports/ decrease as the Zn-content increases in B site. Attributed to the increase in the weak paramagnetic character (Zn ions) while the ferromagnetic character is decreasing (Fe ion), i.e., weakens the inter sublattice (AB) interactions between Fe ions. As the particle sizes are small, the crystallization will be imperfect. The ΔE Q values decrease with increasing Zn content indicating less local distortion at the B sites of ferrite structure 54 . The growth of superparamagnetic doublet due to decreased particle size with increasing Zn content which means a reduction in the bulk magnetization. Due to a large number of nonmagnetic nearest neighbors, the central doublet can be attributed to the magnetically isolated ions which do not contribute to the long-range magnetic ordering 55,56 .
Radiation shielding properties. Transmissions (T) have been calculated using the following formula based on photon intensities (I) and glass thickness (t) for a variety of ferrite samples at various energies 57,58 :    Table 4. ρ (at Rt); T c (K), E a1 (eV) (from Ln ρ) and E a2 (eV) (from Ln σ*T) of investigated nano-ferrite samples.     Fig. 13. There was an exception to this rule in Fig. 13, where mass attenuation values for all samples except for that at 0.081 MeV decrease as Zn content increases from 0 to 0.5 wt%. This may attribute to dominate the Compton scattering in this energy region. Where the probability of a Compton reaction occurring is proportional to Z and photon energy (E) according to Z/E.

X ρ (at Rt) T c (K) Activation energy E a1 (eV) (from Ln ρ) Activation energy E a2 (eV) (from
Radiation shielding design relies heavily on the (T 0.5 ) half-value layer. The thickness of the material required to reduce the incident photon intensity to 50% of its starting value is referred to as this characteristic 60

Conclusion
Magnesium Zinc ferrite was successfully synthesized using the Co-precipitation method and characterized using XRD and FTIR techniques. The XRD patterns confirm the formation of a single phase. XRD data was employed to explore structural properties such as Lattice parameter a exp (Å), crystallite size t (nm), interplanar distance d (nm), X-ray density d x (g/cm 3 ), Bulk density d B (g/cm 3 ), Porosity P (%), Interchain separation R (nm), microstrain (ɛ), dislocation density δ (nm -2 ), and distortion parameters (g). it was found strongly depending on structural parameters with replacement Zn with Mg ions. From FTIR spectra, both ν 1 and ν 2 vibration frequencies for tetrahedral and octahedral sites increased in the range of 609-624 cm −1 and 461-482 cm −1 , respectively, which further employed to calculate force constants. The magnetic hyperfine field and isomer shift strongly depending on Zn in the Mg-ferrite composition. Adding Zn to Magnesium Zinc ferrite MZF-nano-ferrite enhanced density and improved the gamma shielding properties. The µm properties were determined experimentally at 0.

Data availability
All data generated or analysed during this study are included in this published article.