Gamma-Ray Shielding Effectiveness Of Ni-Cu-Zn Ferrite Ceramics: An Alternative To Conventional Shielding Materials

The escalating use of ionizing radiation in medical imaging, nuclear power, and industrial radiography has intensified the need for efficient, non-toxic radiation shielding materials. Traditionally, lead (Pb) and concrete have been the materials of choice. However, lead poses significant environmental and health risks due to its toxicity, while concrete is bulky and requires significant volume for effective attenuation [1]. With ever-increasing use of gamma rays in various fields such as industry, medicine and agriculture etc, the study of photon interaction with different composite materials has become a topic of prime importance for radiation physicists. Some parameters of dosimetric interest are the mass attenuation coefficient, effective atomic number, total photon interaction cross-section and total electronic cross-section. These parameters help in basic understanding of photon interaction with composite materials. The mass attenuation coefficient (µ/ρ) is a measure of number of photons interacting (scattered/absorbed) with target material. It is the fundamental tool to derive many other parameters for dosimetric interests such as mass energy absorption coefficient, molecular, atomic and electronic cross-sections, effective atomic number and density of the materials. Berger and Hubbell have developed a computer program XCOM [2], which is useful for calculation of mass attenuation coefficient and photon interaction cross-section for pure elements and their mixture theoretically in the energy range 1 keV to 100 GeV. Even then, the measurement of mass attenuation coefficient and other parameter is the subject of large interest for many researchers. The theoretical and experimental values of mass attenuation coefficient may or may not agree with each other because of the experimental procedure and conditions. Several researchers have used different composite materials such as Bakelite, cement high Tc superconductor etc, biologically important materials such as plant leaves, bones, proteins etc, for attenuation coefficient of photon [3-4].

Ferrite materials, specifically spinel ferrites (MFeâ‚‚Oâ‚„, where M = Ni, Cu, Zn), have emerged as promising Materials due to their high density, chemical stability, and cost-effectiveness. This study investigates the photon absorption capabilities of Ni0.3Zn0.5Cu0.2Fe2O4 synthesized via solid-state reaction. By evaluating their performance within the 0.360-1.33 MeV energy range-relevant to commonly used isotopes like Ba¹³³, ¹³â·Cs and ⁶⁰Co we analyze the relationship between composition, morphology, and attenuation effectiveness [5]. Among these magnetic materials, soft magnetic materials are used as inductive components in electromagnetic devices viz, transformers of large and small size, telecommunication systems, field sensors in magnetic recording, etc. would determine their suitability of applications in specific electromagnetic devices.  For the low magnetic loss, the high resistivity of the material is needed for various applications. In this regard, spinel ferrite is highly suited for their applications as soft magnetic materials because of low coercive field, high resistivity and low production cost [6]. Therefore, spinel ferrites are considered as a composite material in the present study. Recently, many researchers [7-9] have used the mixture rule in order to provide mass attenuation coefficients for multi-elements. To our knowledge very few researchers [10] have studied mass attenuation coefficient and effective atomic numbers for their use in shielding purpose, Hubbell [11] provided theoretical values of mass attenuation coefficients for various elements.

In the present work, we report our results on linear, mass attenuation coefficient, total atomic cross-section and total electronic cross-section of Ni_0.3Zn_0.5Cu_0.2Fe₂O₄ ferrite composite. The results are verified by Hubble’s mixture rule formula.

2. EXPERIMENTAL PROCEDURE

2.1 Synthesis

The Polycrystalline Niâ‚€.₃Cuâ‚€.â‚…Znâ‚€.â‚‚Feâ‚‚Oâ‚„ ferrite powders were synthesized using the conventional solid-state reaction method [12]. High-purity oxide powders AR grade (NiO, CuO, ZnO, and Feâ‚‚O₃) were stoichiometricly weighed and the constituent oxides of the respective ferrite were, mixed thoroughly. The mixture was well grinded for 3 hours using agate mortar and pestle. The homogeneous mixture is then pressed into a circular pellet of 10 mm diameter and about 2 mm thickness using a hydraulic press. The sample in the pellet form was pre-sintered at 950 ⁰C for 12 hour in a programmable furnace. The samples are then slowly cooled to room temperature at the rate 2 ⁰C per minute. The pre-sintered pellets were again crushed and reground to improve the homogeneity for 2 hours. The dried mixture is compressed in circular pellet form. The polyvinyl alcohol (PVA) was used as a binder. The pellet was then sintered at 1100 ⁰C for 24 hour and finally cooled slow to room temperature at the rate of 2⁰C per minute. The final product obtained in the form of pellet is hard, flat and crack free. The bulk density of prepared spinel ferrite composite Ni_0.3Zn_0.5Cu_0.2Fe₂O₄ is obtained by using mass volume relation is 4.070 gm cm^-3, and the molecular weight of the prepared sample is 238.66. At room temperature, X-ray diffraction (XRD) patterns of sample were obtained by using Philips X-ray diffractometer (Model PW 3710) using Cu-Kα radiations (λ = 1.5405 A⁰). The sample is taken in the form of right circular cylindrical pellets of uniform thickness. These pellets of uniform thicknesses were used to find the linear attenuation coefficient, mass attenuation coefficient of gamma radiation and related parameter for various energies. A narrow beam geometry technique was used to obtain the absorption of gamma radiations. All observations were taken on similar assembly using Scintillation counter and Na(Tl) detector. The linear attenuation coefficient (μ) was measured using a gamma-ray spectrometer equipped. Standard gamma sources (¹³â·Cs at 0.662 MeV and ⁶⁰Co at 1.17 and 1.33 MeV) were used. The intensity of the transmitted radiation was measured both with and without the sample.

3. RESULTS AND DISCUSSION

3.1 X-ray diffraction

The single phase cubic spinel structure of the spinel ferrite composite with the chemical formula Ni_0.3Zn_0.5Cu_0.2Fe₂O₄ has been confirmed by the powder X-ray diffraction technique (XRD). The phase purity and crystallinity were determined using X-ray Diffraction (XRD).

The XRD pattern was recorded on Philips X-ray diffractometer (Model-3710). The X-ray diffraction patterns were recorded using Cu-Kα range, at room temperature. The XRD pattern was recorded in the 2θ range of 20⁰ to 80⁰ with scanning rate 1⁰ per minute.

Fig-1 X-ray diffraction patterns of spinel ferrite composite Ni_0.3Zn_0.5Cu_0.2Fe₂O₄

The values of total mass attenuation coefficient as a function of photon energy and collimator size were calculated from the Hubbell’s mixture rule. The total mass attenuation coefficient for the different materials and energies are determined by the transmission. This process is described by the following equation:

       I = I_oe^-μt                                                            3

where I_o- photon intensity with energy E, without attenuation, I-photon with energy

E, intensity after attenuation

µ_m = µ/ρ (cm²/gm) i.e. mass attenuation coefficient and t (gm/cm²) sample mass thickness (mass per unit area). The total mass attenuation values for materials that are composed of multi elements is the sum of

(μ_m)_i, values of each constituents element by the following mixture rule [14]:

                                                                            4

where, w_i is the weight fraction of i^th element and (μ_m)_i is mass attenuation coefficient of the i^th element. For a material composed of multi-elements, the fraction by weight is given by:

                                                                   5

where, A_i is the atomic weight of the i^th element and n_i is the number of formula units [15].

The theoretically obtained values of mass attenuation coefficient are given in tables 1, 2, 3. A comparison of theoretical and experimental values shows good agreement for the collimator diameter 0.3 cm. The results indicate a clear decrease in μ as photon energy increases, which is consistent with the predominance of the Compton scattering effect in this energy range (0.36–1.33 MeV). The synthesized Ni-Cu-Zn ferrite samples show good agreement with XCOM theoretical values, validating the experimental setup. The attenuation is density-dependent; samples with higher sintering temperatures showed higher density and, consequently, higher μ values.

Table 3

Experimentally measured values of linear attenuation coefficient (µ), mass attenuation coefficient (µ/ρ), total photon interaction cross-section (σ_total), total electronic cross-section (σ_ele) and effective atomic number (Z_eff) for collimated photon beam of 0.4 cm diameter in the energy range (0.360 MeV-1.33 MeV) for Ni_0.3Zn_0.5Cu_0.2Fe₂O₄  ferrite composite.

There is small variation of 1 to 12 % in theoretical and experimental values of total mass attenuation for different collimator sizes. It is observed that, the deviation in experimental and theoretical values of mass attenuation coefficient increases with collimator diameter (0.2 cm to 0.4 cm). Similar observations of mass attenuation coefficient are reported in the literature [14].

3.4   Total photon interaction cross-section

The values of mass attenuation coefficient were used to calculate the total photon interaction cross-section (σ_tot) for the prepared Ni_0.3Zn_0.5Cu_0.2Fe₂O₄ composite material. Following relation was used to calculate the total photon interaction cross-section:

 (barn/atom)                           6

where, µ_m - mass absorption coefficient

1. Atomic weight of sample

N_A- Avogadro’s number 

The values of total photon interaction cross-section for Ni_0.3Zn_0.5Cu_0.2Fe₂O₄ composite spinel ferrite with varying collimator diameter are given in tables 1, 2, 3, and the variation of total photon interaction versus photon energy for collimator diameter 0.2 cm to 0.4 cm is shown in Tables. It is evident that as photon energy increases, the total photon interaction cross-section decreases.

3.5 Total electronic cross-section

The total electronic cross-section for Ni_0.3Zn_0.5Cu_0.2Fe₂O₄ composite spinel ferrite was calculated by using the following relation [16]:

                                             7

where, f_i – denotes the fractional abundance of i^th element with respect to number of atoms such that, f₁+ f₂+ f₃+……+ f_i

 Z_i – atomic number of i^th element.

The values of atomic mass of Ni_0.3Zn_0.5Cu_0.2Fe₂O₄ composite spinel ferrite was used to calculate the total electronic cross-section (σ_ele) and are listed in tables 1, 2, and 3 for varying diameter of collimator.

CONCLUSION

This study successfully synthesized Niâ‚€.₃Cuâ‚€.â‚…Znâ‚€.â‚‚Feâ‚‚Oâ‚„ ferrites using the solid-state reaction method. The evaluation of their radiation shielding properties reveals that these ferrites are effective attenuators of gamma radiation within the 0.360–1.33 MeV range. The close agreement between experimental findings and XCOM theoretical data for collimator diameter 0.3 confirms the validity of the synthesis process. Given their eco-friendly nature and performance, Ni-Cu-Zn ferrites represent a viable, sustainable alternative to lead-based shielding in specific industrial and medical applications where toxicity is a concern.

Ni-Cu-Zn ferrites demonstrate promising photon absorption; particularly Ni₀.₃Cu₀.₅Zn₀.₂Fe₂O₄ their tunable composition and structural stability make them viable for lightweight shielding in medical and aerospace applications. Future work will explore neutron shielding and mechanical durability.

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