Introduction

Ionizing radiation, encompassing photons, protons, and alpha particles, finds widespread applications across various sectors like radiation therapy, nuclear physics, space, and even the field of nutrition, aiming to benefit humanity. However, it poses risks to humans and the surrounding environment, making radiation shielding an imperative consideration. While concrete and lead are universally utilized for ionizing radiation shielding (IRS), they exhibit numerous shortcomings, including a lack of transparency to visible light. Additionally, prolonged exposure to high ionizing radiation energies can cause structural cracks in concrete, and Pb, with its toxicity, heavy weight, and cost, presents further challenges. In light of these issues, scientists and researchers are actively exploring novel materials to replace the aforementioned traditional options, such as alloys1,2,3, ceramics4,5,6, rock or concrete7,8,9, glass–ceramics10,11,12, and glasses13,14,15,16,17,18,19. For instance, glasses find wide-ranging applications due to their ease of preparation and exceptional stability in harsh conditions. Their versatility allows for incorporating a diverse array of oxides through simple substitutions, resulting in an extensive selection of new materials. Glasses, in particular, are widely used in IRS, dosimetry, and lasers20,21,22,23. Glass formers such as phosphorus oxide (P2O5), tellurium oxide (TeO2), antimony oxide (Sb2O3), silicon oxide (SiO2), and boron oxide (B2O3) play important roles in the fabrication of various glass systems24,25,26,27,28. Boron oxide (B2O3) has exceptional features like high transparency, low melting temperature, and remarkable elemental solubility29. The mentioned formers cannot form glass on their own; cannot form glass; they require mixing with other oxides as modifiers. These modifiers play a crucial role in enhancing specific glasses' hygroscopic properties and stability, improving luminescence features, and adjusting the density of glass systems based on their intended applications. Heavy metal oxides such as Bi2O3 are used to improve the optical characteristics and density of glass, thereby improving its IRS properties. For example, Naseer et al. investigated the properties of gamma shielding for TeO2–B2O3–Bi2O3–ZnO composite, drawing comparisons with various concrete variants, commercially available glasses, and assorted glass specimens. The results revealed that the TeO2–B2O3–Bi2O3–ZnO glass demonstrated highly promising shielding capabilities, establishing it as a viable contender for shielding applications30. Halimah et al. investigated the effect of bismuth oxide (Bi2O3) on boro-tellurite glass systems31. The incorporation of Bi2O3 was discovered to improve the glass system's density and mass attenuation coefficient. As a result, their developed glass formulation demonstrated significantly superior radiation shielding properties compared to conventional materials.

This study produced a novel boro-bismuth glass system and enhanced it with varying concentrations of zinc oxide (ZnO) for its potential use in IRS applications. The study comprehensively analyzed the glass system's structural, optical, and IRS properties. The validation of physical properties and characterization by Fourier transform infrared (FTIR) and X-ray diffraction (XRD) were employed to investigate the structural aspects. Simulations were conducted to assess the radiation shielding capabilities using the MCNP-5 code, and the outcomes were cross-referenced with theoretical results derived from the Phy-X/PSD program to validate the findings. In addition to conducting a thorough examination of other essential parameters such as the half-value layer (HVL), mean free path (MFP), tenth-value layer (TVL), and effective atomic number (Zeff) were assessed.

Materials and methods

Glass fabrication

Four glass samples of 50Bi2O3-(50 − x)B2O3 were modified with various ratios of ZnO, whereas x distributions were 0, 5, 10, and 15 mol% and produced by melt quench procedure. Table 1 illustrates the ratios for each element in the current glass composition. The mole ratio was converted to the weight and mixed well for a homogenous powder. After that, the homogenous powder was introduced into the furnace at 1000 °C for half an hour to melt; during the melting procedure, the molten was moved regularly to discharge the bubbles and get homogenous glass which was annealed in another furnace at 350 °C for 3 h. After 3 h, the temperature for the annealing furnace was dropped to reach room temperature.

Table 1 Chemical composition of fabricated glasses.
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Computational radioanalytical software

In this study, we utilized the MCNP5 simulation software, which is well-known for its effectiveness in modeling interactions between gamma and X-ray and particles (electrons and neutrons) with specific materials under defined conditions. Previous research has already established the high efficiency of MCNP5 in assessing radiation shielding parameters32,33,34. To assess the radiation shielding properties for the newly produced samples, we conducted MCNP5 simulations within a 1 m radius sphere filled with dry air, as depicted in Fig. 1. The radiation source was a point source emitting mono-energetic beams positioned vertically on the glass sample's anterior face (along the x-axis direction). To ensure accurate results and eliminate any background radiation interference, precise guidance was provided to the irradiation process using Pb shielding collimators. The simulations were repeated for each sample (S1–S4), varying the mol% of ZnO, and each simulation was performed three times. We meticulously defined relevant data cards and commands, including beam direction (DIR), position (POS), type of particle (PAR), and energy (ERG). Numerous termination steps were implemented to minimize errors and variances, like applying the CUT-OFF option to exclude low-energy radiation (< 1 keV), simplifying the geometry, and raising the number of histories (NPS > 108). We employed a mesh tally (type F4) for energy detection to obtain the cumulative contributions in the designated detecting area.

Figure 1
figure 1

MCNP5 simulation setup (2-D view) of µ/ρ computations obtained from MCNP5 Visual Editor (version X_22S).

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All measurement parameters, such as sample size, distance from detector to source, collimation, and thickness were carefully set based on experimental data to ensure that the simulations accurately aligned with real-world conditions. The calculation shielding indies for the fabricated glasses were performed like equivalent atomic number (Zeq), tenth value layer (TVL), half-value layer (HVL), mass attenuation coefficient (MAC), mean free path (MFP), and fast neutron removal cross-section (FNRCS) were estimated utilizing well-known Phy-X/PSD software within the energy range of 0.015 to 15 MeV35. Phy-X/PSD software available at https://phy-x.net/PSD which has been developed for calculation of parameters relevant to radiation shielding and dosimetry in particular the previously mentioned respectively.

Characterization

Both XRD and FTIR instruments were utilized for the glass sample's structure, whereas Ital Structure APD 2000 diffractometer-XRD was employed to examine the amorphous trend of the synthesized samples. The diffractometer utilized a CuKα X-ray tube (λ = 1.542 Å) with a 40 kV and 20 mA anode current within a 2Ɵ range of 15° to 80°, and a 2°/minute scan rate. The Perkin Elmer instrument-FTIR instrument was used within the wavenumber range from 400 to 2000 cm−1 to reveal the functional group depicted in the fabricated glass samples. Concerning optical properties, UV-V was performed to determine the optical parameters of the glass samples within the range of 200–800 nm. Using the UV edge, various optical properties were calculated, including the bandgap (Eg), optical dielectric constant, molar polarizability (αM), refractive index (n), reflection loss (R), optical molar refractivity (RM), metallization, and electronegativity (χ)36.

Results and discussion

X-ray diffraction (XRD)

Figure 2 presents the XRD results for the Bi2O3–B2O3–ZnO glass system. It shows a broad peak centered at 28°, confirming the absence of long order and pointing to the amorphous behavior of glasses.

Figure 2
figure 2

XRD pattern of xZnO–(50 − x)B2O3–50Bi2O3 glasses.

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Optical properties

The optical properties for xZnO–(50 − x)B2O3–50Bi2O3 glasses were determined by using an absorption edge. The band gap (Eg) was calculated according to Mott and David's relation, and then the Tauc plot was used to extract the Eg values. Table 2 enlists the optical parameter results for all glasses. The relation between Eg and Urbach energy (EU) is also displayed in Fig. 3, where it is evident that while EU values climbed steadily, Eg values decreased as ZnO increased. The decrease in Eg values can be related to creating defects between the conduction and valance bands, such as non-bridging oxygen (NBO). These defects were affirmed according to EU values, which indicate an increase in the disorder with the addition of ZnO. The increase in refractive index values can be related to adding ZnO, which has high refractive index values. Figure 4 illustrates the metallization and the role of ZnO concentrations.

Table 2 Optical parameters of the xZnO–(50 − x)B2O3–50Bi2O3 glasses.
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Figure 3
figure 3

Variation of band gap and Urbach energy as a function of ZnO concentrations.

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Figure 4
figure 4

Variation of metallization criterion with energy gap.

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The addition of ZnO gradually increased the metallization, which showed the benefit of ZnO in improving electrical conductivity by increasing free electrons in the glass structure. The enhancement in reflection loss can be related to reducing energy reflection. At the same time, the increase in molar refractive enhances the polarizability, which is confirmed by the refractive index results. The increment in dielectric constant values with increasing ZnO indicates a rise in the ability to store electric energy in the glass system. The reduction in electronegativity is in line with reduction band gap values, which are meant to grow in the donor centers. Lastly, it can be noted that the decrease in inter-nuclear distance from 6.767 to 4.377 indicates the enhancement of the bond between the nuclei.

FTIR

The centers of the created peaks are shown in Table 3, along with descriptions drawn from the body of literature. The data in the table indicates that Zn+ and Bi3+ exist in tetrahedral and octahedral coordination states, respectively. As a result, Zn+ cations function as glass network formers (GNFs) and Bi3+ cations as glass network modifiers (GNMs) by occupying interstitial vacancies. Moreover, Table 3 shows the two major structural groups of borate glass, BO3 and BO4.

Table 3 Summary of the center and assignment of the observed peaks to the fabricated samples.
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The current results revealed two major distinctive bands, representing both BO4 and BO3 groups. Remarkably, the intensity of the BO3 band is high, while the intensity of the BO4 band is low. Upon scrutinizing all FTIR spectra for the various samples, it was discovered that a decrease in B2O3 content led to a decline in the intensity of BO4 and an increase in the intensity of BO3. This is explained by the fact that oxygen-low oxide (ZnO) has replaced oxygen-rich oxide (B2O3), resulting in a drop in the relative quantity of oxygen atoms. The transformation of BO4 groups into BO3 groups suggests that the glass matrix's degree of crystallinity has increased.

Radiation shielding properties

The simulated mass attenuation coefficient (MAC) for the fabricated glasses with different amounts of ZnO and B2O3 is summarized in Table 4. In the same table, we listed the theoretical MAC data (Phy-X results) for comparison. The obtained MAC values for the prepared glasses are plotted in Fig. 5. From Table 4 and Fig. 5, we can note that the simulated and Phy-X MAC results for the fabricated glasses are in good agreement, and this agreement is correct for any concentration of ZnO and B2O3. For example, the simulated and Phy-X MAC values at 0.15 MeV for the glass with 5 and 45 mol% of ZnO and B2O3 are 1.663 and 1.656 cm2/g, respectively, while for the same composition but at higher energy (5 MeV for example), they are 0.05 and 0.042 cm2/g. Moreover, the below equation was used to calculate the relative difference (RD%) in the simulation process:

Table 4 MAC at particular energies by using MCNP5 and Phy-X.
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Figure 5
figure 5

Changes in the mass attenuation coefficient (MAC) by Phy-X and MCNP5 as the gamma photon energy increased.

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$$RD\%=\frac{MCNP5-PhyX}{(MCNP5+PhyX)/2} x 100$$
(1)

As indicated in Table 4, the RD of MAC results lie in the range 0.106–2.941% for BBZ0, 0.105–4.348% for BBZ1, 0.105–3.398% for BBZ2, and 0.105–2.032% for BBZ3. These RD values are quite low, suggesting that the present MAC results for the synthesized glasses are highly precise. As shown in Fig. 5, the MAC value falls gradually exponentially as energy grows from 0.15 to 15 MeV. As can be noticed in Table 4 and Fig. 5, the MAC value is enhanced in proportion to the rising ZnO content. This rise in the MAC value can be proven by replacing B in the composite with an element with a higher atomic weight, specifically zinc.

The half-value layer (HVL) is a metric that defines the average thickness of the medium needed to reduce a radiation beam's intensity by 50%. The effective atomic number (Zeff) is used in the radiation shielding study of the medium containing elements with different atomic numbers. Both HVL and Zeff give a good indication of the radiation shielding performance of the medium, where high Zeff and low HVL are desirable in practical applications. In Fig. 6a, b, we figured the HVL for the prepared glasses at four energies E1 = 0.5 MeV, E2 = 1 MeV, E3 = 5 MeV, and E4 = 15 MeV. The HVL points to a rising trend as the energy increases from E1 to E3 and reaches the peak at E3, and then the HVL declines with a rise in the energy from E3 to E4. This thickness increases to around 1.6 cm at E2, so we can say it is suitable to use a double-layer sample from each composite, each with a thickness of 0.7 cm to shield the photons with an energy of 1 MeV. Besides, it can be seen that the HVL decreases as we move from BBZ0 to BBZ3, and this is correct at E1-E4. So, including ZnO instead of B2O3 reduced the HVL at any energy. This was mainly due to the increase in the amount of Zn and the decrease in the amount of B, which improved the glass density and then reduced the HVL. Different researchers found that the addition of high atomic number elements instead of low Z causes a decline in the HVL59,60.

Figure 6
figure 6

Zeff and HVL relation for the fabricated glasses at particular energies: E1 = 0.5 MeV, E2 = 1 MeV, E3 = 5 MeV, and E4 = 15 MeV.

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From the data in Fig. 6a, we may conclude that a thinner sample of glass coded as BBZ3 in this work shows better attenuation performance than BBZ0–BBZ2. Concerning Fig. 6b, we can see that the Zeff at E1 and E4 is higher than that at E2 and E3. At E2 and E3, the photons interact with the materials through Compton scattering. In general, the minimum Zeff values have occurred in the Compton scattering region, and for this reason, we found that the Zeff at E2 and E3 are lower than the Zeff at E1 and E4. The following data are the minimum values for the Zeff for the BBZ0-BBZ3 glasses and reported at (E2: 27.15, 27.96, 28.82, and 29.73), respectively. Meanwhile, at E4, the photons interact with the glass samples through pair production. This procedure relies on the atomic number of Z2, so we can see that the Zeff increases at E4. Moreover, at any of the selected energies (E1–E4), the Zeff shows a positive dependence on the amount of the ZnO content. The Zeff for BBZ3, which contains a high concentration of ZnO, is higher than the Zeff of the low ZnO content samples. From Fig. 6a, b, the high ZnO content plays a crucial function in increasing the shielding performance of the glasses and getting glass with lower thickness. In Fig. 7, we matched the HVL for BBZ3 with lead, RS 520 glass, and iron at 0.5, 1, and 5 MeV61. The comparison data shows that the HVL at 0.5 MeV for BBZ3 is higher than that of lead. This also means that the lead has a better attenuation attitude than BBZ3, which is expected due to the high density of lead. Also, this means that the lead has a better attenuation attitude than BBZ3 and this is expected due to the high density of lead. At 1 MeV, the HVL of BBZ3 is also less than the HVL of lead, and a similar result is found for E = 5 MeV. But, when we compare the HVL for BBZ3 with that of iron, we found that the HVL of BBZ3 is smaller than that for iron at 0.5, 1, and 5 MeV, which suggests that we need a lesser thickness of BBZ3 to attenuate 50% of the radiation in comparison with the thickness needed from the iron. The results in this figure also explain that the HVL of BBZ3 is lower than that of RS-520 glass, which is correct at the three selected energies. So, BBZ3 needs a smaller thickness to accomplish a similar level of shielding as iron and RS 520 glass, implying good radiation shielding performance of BBZ3 glass compared to iron and RS-520 glass.

Figure 7
figure 7

Comparison between the HVL for BBZ3 with lead at 0.5, 1, and 5 MeV respectively.

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Figure 8 compares the fast neutron removal cross-section (ƩR) for present glasses and standard substances. The ƩR for glasses showed enhancement from 0.105 to 0.109 cm−1 with adding ZnO. At the same time, the ƩR for traditional materials, including water, graphite, and concrete, are 0.102, 0.094, and 0.077 cm−1. In addition, Table 5 compares ƩR results that were manually calculated, and from the Phy-X program, the results showed high compatibility between the two procedures. Table 5 and Fig. 8 show that the fabricated glasses were superior standard materials, nominating present glasses for use in the radiation shielding field.

Figure 8
figure 8

ƩR of the fabricated samples with some common shielding substances.

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Table 5 Fast neutron removal cross-section of the prepared samples.
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Neutron scattering and absorption parameters are crucial in describing how neutrons interact with materials. These characteristics are critical in various domains, such as nuclear physics, materials science, and engineering. The chance of neutrons interacting with materials and changing their direction or energy is referred to as neutron scattering parameters. The scattering cross-section, which measures the opportunity of a neutron interacting with a target nucleus and being scattered in a specific direction, may describe these values. The scattering cross-section is determined by the neutron's energy and the atomic characteristics of the target substance. The chance of neutrons being absorbed by matter, which can result in the target nucleus becoming excited or conducting a nuclear reaction, is referred to as neutron absorption parameters. The absorption cross-section quantifies the likelihood of a target nucleus absorbing a neutron. The absorption cross-section is also affected by the neutron's energy and the atomic characteristics of the target substance. Neutron scattering and absorption characteristics are significant in constructing and operating nuclear reactors because they govern the pace of neutron interactions and energy production. They are also helpful in materials science, where they can be used to analyze substances' atomic structure and characteristics and Fig. 9 shows neutron absorption and scattering parameters for glasses. The incoherent neutron scattering length (binc) and the incoherent neutron scattering cross section (σinc) showed enhancement with increasing ZnO. While the coherent neutron scattering length (bcoh), the coherent neutron scattering cross section (σcoh), the total neutron scattering cross section (σtot), and the absorption neutron scattering cross section (σabs) were reduced with increasing ZnO, indicating a low role for ZnO in stopping neutrons.

Figure 9
figure 9

The neutron scattering and absorption parameters for newly prepared samples (σabs: the absorption neutron scattering cross section, σcoh: the coherent neutron scattering cross section, bcoh: the coherent neutron scattering length, σinc: the incoherent neutron scattering cross section, binc: the incoherent neutron scattering length, and σtot: the total neutron scattering cross section).

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The mass stopping power (MSP) for alpha and proton was computed to investigate the shielding parameters of charged particles using SRIM software which avalibal at the following link http://www.srim.org/62. The Fig. 10a, b indicate a noticeable increment in MSP for alpha and proton respectively within the kinetic energy range of 0 to 1 MeV, followed by a gradual decrease in MSP within the kinetic energy range of 1 to 10 MeV. The addition of ZnO had an apparent effect on the MSP values, leading to a reduction in the MSP values. The decline in MSP values is related to the decrease in the glass efficiency in stopping charged particles due to adding heavy atom Zn instead of low atom B. As known, the heavy atoms have tightly bound electrons in lower levels, reducing the absorption of charged particles.

Figure 10
figure 10

(a) MSP of the proton and (b) MSP of the alpha for the prepared glasses.

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The term "projectile range" in the context of charged particles indicates the maximum distance that a charged particle can traverse across a material until it dissipates all of its energy and eventually stops. The distance a charged particle can cover before stopping, i.e., its range, is influenced by several factors, such as the particle's type, energy, the density and mass of the material, and the characteristics of the interactions between the particle and the substance. The projectile range for proton and alpha particles are shown in Fig. 11a, b respectively. The values of the projectile range increased with increasing kinetic energy for charged particles.

Figure 11
figure 11

(a) Proton projected range of the proton and (b) proton projected range of the alpha for the prepared glasses.

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Conclusion

In the present work, we extensively studied the radiation shielding abilities of the Bi2O3–B2O3–ZnO glasses against alpha/proton, neutron, and photon radiation. The structure of the glass system was explored to check its nature and vibrational bands. The optical parameters were also assessed to determine the optical parameters. The density showed enhancement with substituting B2O3 by ZnO, and its values are 5.981, 6.182, 6.312, and 6.433 g/cm3 for BBZ0, BBZ1, BBZ2, and BBZ3, respectively. The XRD results showed the broad peaks affirming the amorphous nature of the glass system. At the same time, the FTIR revealed several bands that are related to B2O3 and Bi2O3. The direct Eg values for BBZ0, BBZ1, BBZ2, and BBZ3 are 2.831, 2.322, 2.214, and 2.091 eV. Phy-X/PSD and MCNPX computations were utilized to simulate the fundamental photon attenuation parameter, or MAC, for the energy range of 0.015 to 15 MeV. The MAC values at 0.015 MeV increased progressively from 90.84 to 93.16 cm2/g when the ZnO insertion ratio in the glasses grew from 0 to 15 mol%. Among the glasses, BBZ3 glass (with 15 mol% ZnO) exhibited the highest MAC values, ranging from 93.16 to 0.049 cm2/g. Consequently, compared to the other glasses, the BBZ3 glass with the greatest ZnO content showed better photon attenuation characteristics. This result was further supported by the high Zeq and low EBF values observed for BBZ3 glass. Furthermore, we observed that BBZ3 glass, with the highest density (6.433 g cm−3), possessed a more significant ƩR-value (0.109 cm−1) than the other glasses. It was clear that BBZ3 glasses performed well in terms of neutron shielding when compared to conventional materials like water and regular concrete, which have ƩR consequently values of 0.102 and 0.077 cm−1. We found the stopping power for interactions between charged particles (protons and alphas) and BBZ glasses in the 0.01–10 MeV kinetic energy range. The findings showed that all BBZ glasses had comparable stopping powers for charged particles. Overall, the conclusions of this work contribute significantly to the existing literature and enhance our understanding of the radiation reduction abilities of bismuth-borate glasses.