Structural, Optical, Magnetic and Photon Attenuation of Novel Potassium Lead Borate Glasses Doped with MnO

Potassium lead borate glasses doped with MnO (40B2O3 + 40PbO + (20-x)K2O + xMnO: x = 0–5 mol%) have been prepared via standard melting quenching process. The impact of MnO on the structure, optical, magnetic and gamma-ray protection properties of pottisium lead borate glasses have been examined. The density was increased from 4.83to 5.23 g/cm3 as MnO content increased while the molar volume of prepared glass sample was decreased from 28.112 to 25.755 cm3/mol. The obtained direct optical gap (Eg) values were 2.84, 2.59, 2.41, 2.19, 1.95, and 1.84 eV for the Mn-x (x = 0, 1, 2, 3, 4, and 5) glass samples, respectively. Fourier-transform infrared spectroscopy (FTIR) spectra demonstrated that as the MnO concentration increases in the glass network the intensity and width of the IR bands were increased. The magnetic measurement revealed that the magnetic saturation (Ms) was decreased while the magnetic coercivity (Hc) was increased with increasing MnO substitution ratio. The linear attenuation coefficient of the μMn-glass\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mu }_{Mn-glass}$$\end{document} follows the order: µMn-0 < µMn-1 < µMn-2 < µMn-3 < µMn-4 < µMn-5. Half value layer (HVL) rises as µ decreases and vice versa. The range of the HVL is 0.002–3.378, 0.002–3.334, 0.002–3.291, 0.002–3.248, 0.002–3.176, and 0.002–3.106 cm for Mn-x (x = 0, 1, 2, 3, 4, and5). The trend of effective atomic number (Zeff) variation is related to that of both linear and mass attenuation coefficients (µ and µm). The produced Mn-glasses can be employed in a variety of optical, magnetic and radiation protective applications.


Introduction
Because of their wide range of applications, glasses offer a distinct advantage over other types of materials. Optical fibres, solid state lasers, water treatment, and optical filters considered as examples of technological and biological applications of glasses [1][2][3][4][5][6][7][8][9]. A growing number of studies have looked into the subject of glasses. Because of the distinctive physical, chemical, electrical, magnetic, and optical characteristics of boron-based glasses, the number of research and investigations has increased dramatically. These glasses have a significant glass-forming nature and low softening and melting temperatures. Furthermore, boron-based glasses are known to have a variety of amazing characteristics including high electrical conductivity, high thermal expansion coefficients, low thermal conductivity, and low dispersion [7]. All these properties make boron glasses have more advantageous compared to further conventional glass formers for instance phosphate, germanate and silicate [6][7][8][9].
The effects of manganese (Mn) ions on the physical and structural features of diverse glass systems such as borate, tellurite, and phosphate have been studied by a number of researchers [10][11][12]. Manganese has more stable valence states such as Mn 2+ , Mn 3+ , and Mn 4+ [13]. Only Mn-containing glasses had the second and third oxidation states. Mn 2+ ions in the glass network have a significant influence on optical characteristics [14].
Recently, glasses contain heavy metal oxide (HMO) such as PbO and Bi 2 O 3 have more attention from several technologists, researchers, and investigators due to their interesting structural, physical and physiochemical characteristics like as substantial improvements in their linear/nonlinear optical features and radiation protection application [15][16][17][18][19][20].
The aim of the present work is to investigate the impact of MnO substitution in structural modifications, optical parameters such as optical energy gap and Urbach energy of the prepared potassium lead borate glasses doped with MnO. Magnetic properties of the prepared glasses have been studied. In addition, gamma-ray shielding parameters such as mass attenuation coefficients, linear attenuation coefficient and effective atomic number of the prepared glass haven been evaluated.

Measurements and Calculation
In the current study, Archimedes' technique (Eq. 1) was used to determine the densities of Mn-glasses with toluene as an immersion liquid with density (ρ toluene ). Considering W b is the weight of glasses in toluene liquid, and W a is the weight of the glasses in air, the glass density can be given by: The infrared absorption spectra of the produced Mnglasses were measured at room temperature in the range 4000-400 cm −1 via an infrared spectrometer type Jasco FTIR-300E (Japan).
In order to evaluate the optical data of the polished prepared Mn-glass samples, Cary 5000 UV-Vis-NIR double beam spectrophotometer was used.
Using the vibrating sample magnetometer (VSM), the magnetic hysteresis characteristics of the prepared glasses in magnetic fields with intensities up to 20 kOe at room temperature.
All gamma radiation shielding parameters presented in the current work were evaluated by Phy-X/PSD software [21] as: Mass attenuation coefficients (MAC = µ/ρ) and linear attenuation coefficient (LAC) were estimated by using eqs.
(2) and (3), respectively; µ and µ/ρ were used to calculate the half value layer (HVL) and effective atomic number (Z eff ) as follows:  Fig. 1 Density and molar volumeas a function of MnO content of 40B 2 O 3 + 40PbO + (20-x)K 2 O + xMnO: x = 0, 1, 2, 3, 4, and 5 mol% respectively. The difference in density between MnO (5.37 g. cm −3 ) and K 2 O (2.35 g.cm −3 ) causes an increase in the density of glass samples as MnO content increases. In contrast the molar volume of prepared glass sample was decreased with increasing Mno substitution ratio ( Table 1). The FTIR spectra of the fabricated glass samples with the composition 40B 2 O 3 + 40PbO + (20-x)K 2 O + xMnO (x = 0, 1, 3, and 5 mol%) were recorded at room temperature in the spectral region of 400-4000 cm −1 and presented in Fig. 2. The vibrational modes of the glass samples under investigation may be divided into three infrared spectral ranges [22,23,23]. Asymmetrical stretching vibrational modes occurring in the B-O band of the trigonal [BO 3 ] units can be attributed to the first region in the range of 1200-1800 cm −1 . The stretching vibrations occurring in the B-O band of the tetrahedral [BO 4 ] units are described in the second area, which ranges 800-1200 cm −1 . The third band is seen between 400 and 800 cm −1 is ascribed to the bending vibrations of different borate arrangements and the vibration of metal cations like Pb 2+ , K 1+ and Mn 2+ across the glass network. Table 2 depicts the vibrational groups in IR spectra in the spectral region of 400-4000 cm −1 [24,25]. Many peaks have been resolved for all of the samples using the deconvoluted spectra, as shown in Fig. 3a-d. The peak position (x c ), amplitude (A), and full width at half maximum (W) of the peaks produced from the deconvolution technique are shown in Table 3. The deconvoluted spectra of the different samples demonstrate that as the MnO 2 concentration increases in the glass network the intensity and width of the IR bands were increased. This is attributed to a higher degree of disorder when more Mn 2+ ions access the network and serve as structural modifiers. This results in a significant increase in the amount of non-bridging oxygen  atoms, which has an impact on the structural stability of the glass system [26]. On the basis of the following discussion, it can be assumed that the addition of MnO in place of K 2 O resulted in structural modifications. The absorbance spectra of the prepared Mn-glasses are shown in Fig. 4. It was clear that the optical absorption edge is shifted to higher wavelength with the increase of MnO content in the prepared glasses. According to the absorption spectra, the optical band gap (E g ) values are evaluated in the context of a Tauc's relation between absorption coefficient α(ν) and the photon energy (E = hν) as Eq. (6) [27]:

Density, FTIR Analysis, and Optical Properties
where K is a constant and s may has the following values 2, 3, 1/2 and 1/3 depending on the type of electronic [28]. Herein, we used s = 1/2 indicating the direct electronic transition. Because of the predominant transitions in glasses are direct or indirect which acquire the absorption of photons near the E g [29]. Variation of (αhν) 2 with (hν) of the prepared Mn-glasses is shown in  Table 4, it is obvious from these values that a further doping of MnO results in a reduction in E g values. This reduction in E g values is linked with the increased content of non-bridging oxygens (NBO) within the glass matrix [30,31].
Urbach's empirical formula is given by Eqs. (7) and (8) [32]: where α is absorption coefficient and E u is the urbach energy. As a result, the slope of the straight line obtained by plotting ln(α) versus (hv) gives the Urbach's energy (E U ). The variation of (lnα) with (hν) of the prepared Mn-glasses is plotted in Fig. 6. Values of Urbach's energies were evaluated and listed in Table 4. The E U values were increased with the increasing of MnO content in the prepared Mn-glasses. This result revealed that with increasing MnO concentration in the prepared glasses, there was less stability in glass samples with more imperfections and increase disorder in the produced glass samples. Figure 7 shows the magnetization of prepared glass samples doped with MnO as a function of magnetic field. It was detected that undoped glass and doped glass samples with MnO exhibited a soft ferromagnetic behavior. Table 4 represents the values of saturation magnetization (M s ) and coercivity field (H c ) which estimated from the hystresis loop curve.

Magnetic Properties
As well as the magnetic moment per formula unit in Bohr magnetons (μ B ) was calculated by using the following relation (9) [33] and listed in Table 4:  where M is the molecular weight of the composition. At the beginning of the MnO substitution there was a rapid decrease in saturation magnetization (M s ) and magnetic moment until Mn-2 and after that there is some improvement in the (M s ) and (μ B ), but still the sample Mn-0 has the best in saturation magnetization and magnetic moment. On the contrary, at the beginning of the replacement, the coercivity field (H c ) was improved until Mn-2, and then this improvement was decreased, but it is still better than Mn-0.
The decreasing of saturation magnetization (M s ) and magnetic moment (μ B ) with increasing MnO substitution ratios might be attributed to an increase in anti-ferromagnetic phase with a smaller ratio of ferromagnetic-like phase.

Mn-Glasses as Gamma-Ray Protection Materials
Phy-X/PSD software [21] was used to evaluate the gamma radiation protection parameters. Figure 8 depicts the energy response of the (LAC = µ) of the prepared Mn-glasses. From Fig. 8, it was seen that µ reduces smoothly with 0.10 ≤ photon energy (E) ≤ 8 MeV. Then, the values of µ slightly increased at 10 MeV. This trend demonstrates the reduction and increase in the photon interaction cross-sections of the Mn-glasses with respect to photon energy. Typically, within the investigated energy spectrum: where, PE = the linear attenuation due to photoelectric (PE), CS = the linear attenuation coefficient due to Compton scattering (CS), and PP = the linear attenuation coefficient due to pair production (PP) absorption processes, respectively. The contribution of eah of these absorption processes at different energies gives the general behaviour of µ. According to energy, PE ∝ E −3 , CS ∝ E −1 , and PP ∝ E 1 . Consequently, the energy spectrum of the µ can be divided into three regions where each of the i dominates photon interactions. The PE dictates the energy response of µ at 0.10 ≤ photon energy ≤ 0.5 MeV, the CS dicates the energy response of µ at 0.5 < photon energy ≤ 8 MeV, while the PP dicates the energy response of µ at 0.8 < photon energy ≤ 10 MeV. Thus the rapid decay in the value of µ in the low energy range is due to PE ∝ E −3 , while the slight increase in the µ is as a result of the energy dependence of PP . Results of the Mn−glass follows the order: µ Mn-0 < µ Mn-1 < µ Mn-2 < µ Mn-3 < µ Mn-4 < µ Mn-5 . Generally, ∝ , hence, the observed trend of µ can be attributed to the increase in the mass density (ρ) of the glasses as MnO content increases relative to K 2 O. The (µ m ) of the prepared Mn-glasses is shown in Fig. 9. The behavior in the energy response of m is similar with that of µ due to m ∝ . Furthermore, the energy dependence of ( m ) PE , ( m ) CS , and ( m ) PP at each energy prescribe the overall energy response of m of the glasses. Thus the trend of m at each energy is such that ( m ) Mn-0 < ( m ) Mn-1 < ( m ) Mn-2 < ( m ) Mn-3 < ( m ) Mn-4 < ( m ) Mn-5 . Another useful radiation shielding parameter is the HVL used to describe the relative photon shielding power of a material. HVL is the required thickness of the glass to reduce incident photon exposure to 50%. Figure 10 demonstrates the variation of HVL with the photon energy and MnO concentration in the prepared Mn-glasses. Quantitatively and qualitatively, the variation in the values of HVL is consistence with the inverse of µ. For energies where photon interaction probability decreases, HVL rises and vice versa. Hence, HVL rises as µ decreases and vice versa. The range of the HVL is 0.002-3.378, 0.002-3.334, 0.002-3.291, 0.002-3.248, 0.002-3.176, and 0.002-3.106 cm for Mn-0, Mn-1, Mn-2, Mn-3, Mn-4, and Mn-5, respectively. Clearly, the gradual replacement of K 2 O with MnO improved the photon absorbing capacity of the glasses.
Finally, the impact of adding MnO to the prepared Mnglasses on the effective atomic number (Z eff ) is studied. The variation of Z eff as a function of photon energy (MeV) and MnO content for the prepared Mn-glasses is depicts in Fig. 11. It is clearly that according to relation (5), the trend of Z eff variation is similar to that of both linear and mass attenuation coefficients (µ and µ m ).

Conclusion
The impact of adding MnO to the prepared Mn-glasses with chemical composition 40B 2 O 3 + 40PbO + (20-x) K 2 O + xMnO: x = 0-5 mol% on structure, optical, magnetic and gamma-ray protection properties have been examined. Results revealed the following items: 1-The density of the Mn-glasses was increased from 4.83 ± 0.01 g/cm 3 to 5.23 ± 0.01 g/cm 3 as MnO content increased from 0 to 5 mol%. 2-The obtained direct E g values were 2.84, 2.59, 2.41, 2.19, 1.95, and 1.84 eV for the Mn-0, Mn-1, Mn-2, Mn-3, Mn-4, and Mn5 glass samples, respectively. 3-The deconvoluted spectra of the investigated samples demonstrate that as the MnO 2 concentration increases in the glass network the intensity and width of the IR bands were increased. As well as a higher degree of disorder occurred when more Mn 2+ ions access the network and serve as structural modifiers. 4-There is more agreement between the results of FTIR and UV-Vis data. 5-The magnetic measurements showed that the coercivity field (H c ) was improved by increasing MnO substitution ratio. 6-Results of the Mn−glass follows the order: µ Mn-0 < µ Mn-1 < µ Mn-2 < µ Mn-3 < µ Mn-4 < µ Mn-5 . 7-HVL rises as µ decreases and vice versa. The range of the HVL is 0.002-3.378, 0.002-3.334, 0.002-3.291, 0.002-3.248, 0.002-3.176, and 0.002-3.106 cm for Mn-0, Mn-1, Mn-2, Mn-3, Mn-4, and Mn-5, respectively. 8-The trend of Z eff variation is similar to that of both linear and mass attenuation coefficients (µ and µ m ).
One can conclude that the prepared Mn-glasses can be used in several optical and radiation protection areas.
Funding The authors have not disclosed any funding.