Introduction

Borosilicate glasses are considered low-cost materials that are available commercially in large quantities by several vendors. These glasses are used for many applications such as optical devices, nuclear materials, and in the electronics industry, glasses which have high transparency in the visible area are one of the suitable absorbers in terms of radiation shielding properties. (Fe2O3-SiO2-B2O3-Al2O3-Na2O) glasses have been studied by many authors that is because of the unique physical structural, mechanical, and optical properties (Ref 1,2,3,4). Alumino alkali borosilicate glasses containing Fe2O3 are excellent mechanical and thermal properties. Glasses doped with transition metal ions (TMI), such as iron, exhibit high optical, mechanical, and electrical properties because it has more than one valence state (Ref 5). Additionally, Fe2O3 can be used to color the host glass, when added in small quantities, due to its position in the glass matrix and capability to modify its network (Ref 6, 7). B2O3 is used as a glass network forming not only because of easy preparation but also because it is doped with many modifying oxides such as (TM) (Ref 8). In other words, intermediate oxides glasses like Al2O3 play a double role as glass modifier or glass former, this is depending on their concentration in the glass structure. The presence of Al2O3 increases the physical properties such as thermal stability and mechanical properties (Ref 9). Studying the thermal stability of glasses is very interesting in science and technology; these are important for composite material of glasses (Ref 10, 11). Glasses and glass-ceramics belong to advanced functional materials. The processing, properties, and applications of these materials have been presented and discussed in the excellent book published recently by Karmakar (Ref 12). Their electrical, mechanical, thermal, and optical properties depend significantly on the local structure of the glass-host (Ref 13). The structure and properties can be changed drastically during the transformation from glasses to glass-ceramics under the heat treatment process (Ref 14). One problem encountered in making glass-ceramics is to establish a surface quality required for disk substrate and the other problem in making their parent glasses is to establish a good glass formation excluding devitrification or crystallization (Ref 15). Glass-ceramics are useful materials. The processing, properties, and applications of these materials have been presented by many researchers (Ref 16,17,18,19). Beall (Ref 20) described machinable glass-ceramics containing phlogopite from the SiO2-B2O3-MgO-Al2O3-K2O-F glass system. Grossman (Ref 21) obtained a tetra silica–mica glass-ceramics from the K2O-MgF2-MgO-SiO2 glass system. The structure of phlogopite is [SiO4]- and [AlO4]- tetrahedra, forming a hexagonal ring. Gautam et al. (Ref 22, 23) studied optical and electrical properties of (PbxBi1-x), TiO3 borosilicate glass, and glass-ceramic systems. Glass-ceramics are made by two steps, the one is the heterogeneous nucleation and the second is the crystal growth in which more than fifty of the glass are converted to crystal. This process allows fabricating a new material having unique and useful properties. Glass-ceramics are used in our life as cookware, tableware, stove-tops, and low expansion printed circuit boards. This work aimed to fabricate the glass system with the formula xFe2O3-35SiO2-35B2O3-10 Al2O3-(20 − x) Na2O, (0 ≤ x ≤ 1 mol.%). Following this preparation, certain properties of the glass system were tested, including thermal and mechanical properties. The corresponding glass-ceramic has been fabricated. Following this preparation, certain properties of the glass-ceramics were tested, including mechanical properties, and investigated by XRD, TEM. The elastic moduli of the prepared glasses and glass-ceramics was tested experimentally by measuring the ultrasonic wave velocities at 4 MHz.

Experimental Procedures and techniques

Five borate glass samples with the chemical formula xFe2O3-35SiO2-35B2O3-10 Al2O3-(20 − x) Na2O, (0 ≤ x ≤ 1 mol.%) have been prepared by melting quenching technique. Pure Fe2O3-SiO2-B2O3-Al2O3 and Na2O were ground to obtain a mixture for each of the glass samples. The powders produced were then melted in an electrically heated furnace at about 1200 °C in regular atmospheric pressure in Pt crucibles, for four hours to homogenize the melt, which was then added to a preheated mold. This mold was moved right away to a different furnace heated to 500 °C for 2 h to anneal the glass. Table 1 presents the starting mixtures, also known as nominal composition. Weight loss was minimal with a value of less than 0.5%. The prepared samples’ thickness was 1 cm, and each was polished by its use to measure elasticity. The pulse-echo technique was applied at room temperature to measure ultrasonic velocities. In this technique, x-cut and y-cut transducers of 4 MHz. The ultrasonic velocities had a ± 10 m/s uncertainty of measurement. Determining the density (ρ) of the assembled glass and glass-ceramic samples was done at room temperature using the Archimedes method. FT-IR spectroscopy of the prepared glasses samples at room temperature with the range 400-4000 cm−1 by spectrometer type JASCO 430. Thermal analysis of samples is obtained by using DTA Shimadzu 50 at a rate 10 °C/min over the range of 800 °C in nitrogen medium. The glass-ceramic is prepared by heating the sample in a two-step regime at two specified temperatures; the first step is nucleation at temperature range 475 °C with rate 20 °C/min and holding to 2 h for the creation of nuclei sites. The second step is crystal growth by heating the samples at Tc  °C temperature at the same rate and holding to 1 h. X-ray diffraction patterns were obtained by Philips x-ray diffractometer (PW/1710 with Ni-filtered Cu-Kα and radiation λ = 1.542 Å) for glass and glass-ceramic. The transmission electron microscope (TEM) of the type (JEM-100 CX 11 JAPAN) has been utilized to determine the crystallinity and the particle size in glass-ceramics samples. The scanning electron microscope (SEM) of the type (JEM-100 CX 11 JAPAN) has been utilized to study the morphology of the investigated glasses.

Table 1 Chemical composition of the prepared glasses (mol.%) and optical band gap of the prepared glasses
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Results and Discussion

XRD of the Prepared Glasses

Figure 1 illustrates the x-ray diffraction of the prepared glass samples. It can be concluded, from the x-ray diffraction curves, that the samples tested have a high level of glassiness. This was seen in the existence of bumps 2θ ~ 30° and the absence of discrete lines and sharp peaks. Some series of peaks were not as broad as others; however, no amount of the samples was in the crystalline phase.

Fig. 1
figure 1

XRD of the studied glass system

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FT-IR Analysis

Previously FT-IR spectra have been used to studying on alkali borosilicate glasses; it is discovered that the structure of these glasses is dependent on the content of the alkali oxide and silicon, and boron ion (Ref 24,25,26,27,28,29,30,31,32,33,34,35,36,37). FT-IR spectrum of the sodium aluminum borosilicate glass holding different Fe2O3 concentrations is illustrated in Fig. 2. The main absorption spectra of sodium aluminum borosilicate glasses are summarized as; (Ref 24,25,26,27,28,29,30,31,32,33,34,35,36,37).

Fig. 2
figure 2

IR spectra of the prepared glasses

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  1. 1

    Bands at 400-600 cm−1 associated with Si-O-Si and O-Si-O bending modes, B-O-B bending and Al-O, and normal vibration of Fe-O bond in the deformed FeO6 octahedral.

  2. 2

    Bands around 600-800 cm−1 are accredited with Si-O-Si symmetric stretching of bridging oxygen between tetrahedral, B-O-B vibrational, and Al-O bend in AlO6 units; the symmetric stretching vibration of the Fe-O bonds in the [FeO6] groups.

  3. 3

    Bands around 800-1200 cm−1 associated with Si-O-Si antisymmetric stretching of bridging oxygen within the tetrahedral and B-O stretch in BO4 units from diborate units.

  4. 4

    Bands around 1200-1450 cm−1 associated with B-O stretch in BO3 units.

The deconvolution parameters of the bands for the investigated glasses along with their assignments are given in Table 2 and Fig. 3 and 4. Peak assignments for the prepared glasses are given in Table 3.

Table 2 De-convolution parameter of the infrared spectra of studied glasses, (C) is the band center and (A) is the relative area (%) of the component band, BO4, BO3, and N4
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Fig. 3
figure 3

IR spectra and curve-fitting of the glasses number G1

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Fig. 4
figure 4

IR spectra and curve-fitting of the glasses number G5

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Table 3 Peak assignments for the prepared glasses
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Density of glasses and glass-ceramics

The density of the prepared glasses and the glass-ceramics is determined by Archimedes’ principle as the following relationship:

$$\rho = \rho_{0} \left( {\frac{C}{{C - C_{1} }}} \right)$$
(1)

where ρ is the density of the samples, \(\rho_{0}\) is the density of toluene, 0.865 g/cm3, and C and C1 are the weights of the samples in air and toluene, respectively. The density value of the glass sample depends on the density of both Na2O and Fe2O3 [2.27, 5.25], and the difference in their molecular weights [61.69, 159.688], respectively. So, the density value of the glass sample is increased by the concentration of Fe2O3 increase. The density values are shown in Fig. 5.

Fig. 5
figure 5

Density of glass and glass-ceramic against of Fe2O3 by mol. %

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The density of glass-ceramics has been estimated and the value of densities is shown in Fig. 5. The density of the studied glass-ceramics increases by heat treatment. The density of the prepared glass-ceramic samples is larger (Ref 38) than of the parent glass. I think that heat treatment relaxes the glass structure by released some of its internal energy, the thing which causes some order and compactness structure. Therefore, different proprieties should appear, and the density increases.

Mechanical Properties of the Glass and Glass-Ceramics

It is important to note the mechanical properties of materials, especially solids, since this helps in their use in science, as well as various technological applications. The concept of elastic moduli is important to understand the arrangement changes in materials (Ref 39, 40). The sound velocities of the glass system (vL) and (vT) are presented in Fig. 6. It was found that the two velocities (vL and vT) increased with the increase in the content of Fe2O3 in the new glass system. The present investigation confirmed that the longitudinal velocity (vL) increased from 5180 to 5310 ms−1 and that the shear velocity (vT) and vT increased from 2980 to 3060 ms−1. The sound velocities of the glass system (vL) and (vT) are presented in Fig. 6. It was found that the two velocities (vL and vT) increased with the increase in the content of Fe2O3 in the new glass system. These increases in the sound velocities may be associated with an increase in the density and cross-link density.

Fig. 6
figure 6

Dependence of the longitudinal and shear ultrasonic velocities vL and vT of the investigated glasses and glass-ceramics

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As well as the sound velocities of the glass-ceramics (vL) and (vT) are presented in Fig. 6. It was found that the two velocities (vL and vT) increased with the increase in the content of Fe2O3 in the new glass system. The present investigation confirmed that the longitudinal velocity (vL) increased from 5210 ms−1 to 5385 ms−1 and that the shear velocity (vT) and vT increased from 2990 ms−1 to 3075 ms−1. The sound velocities of the glass-ceramics are larger (Ref 38) than of the parent glass. I think that heat treatment relaxes the glass structure by released some of its internal energy, the thing which causes some order and compactness structure. Therefore, different proprieties should appear, and the velocities of the glass-ceramics increase. To determine the elastic moduli, the following relations (Eqs 2-5) were used:

$${\text{Longitudinal}}\,{\text{modulus}},\quad L = \rho v_{l}^{2} ,$$
(2)
$${\text{Shear}}\,{\text{modulus}},\quad G = \rho v_{s}^{2} ,$$
(3)
$${\text{Young's modulus}},\quad Y = \left( {1 + \sigma } \right)2G,$$
(4)
$${\text{Bulk}}\,{\text{modulus}},\quad K = L - \left( {\frac{4}{3}} \right)G.$$
(5)

Theoretical Model

The elastic moduli of glasses may be computed according to a Makishima–Mackenzie (Ref 41, 42) model based upon the dissociation energy of bonds and ionic radii of the elements. They derived an applicable semiempirical formula for the calculation of Young’s modulus (Yth)and the bulk modulus (Kth) based on the chemical composition of the explored glass, the packing density of atoms Vt; and the bond energy per unit volume or the dissociation energy, Gi as;

$$Y = 2Vt\sum\limits_{i} {G_{i} x_{i} }$$
(6)
$$K = 100V_{t}^{2} \mathop \sum \limits_{t} G_{i} X_{i}$$
(7)
$$V_{t} = 1/V_{m} \mathop \sum \limits_{i} V_{i} x_{i}$$
(8)

where xi is the mole fraction of component i. The packing factor Vi of oxide AmOn having ions A and O with Pauling radii (RA and RO) is given by

$$V_{i} = \frac{4\pi }{3}N_{\text{A}} \left( {mR_{\text{A}}^{3} + nR_{\text{o}}^{3} } \right)$$
(9)

where RA and RO are the respective Pauling ionic radii of metal and oxygen and NA Avogadro number.

The various types of elastic moduli of glasses (experimentally and theoretically) and glass-ceramics were determined. They were recorded in Fig. 7, 8 and 9. These values display an increasing trend with higher Fe2O3 mol.%. This is an indication of the improvement in the rigidity of the investigated glass systems. Such behavior is mainly due to the change within the coordination variety with higher Fe2O3 mol.%, the increase in the common force between the molecules, and the replacement of Na-O with Fe-O linkages. The bond strength of Na-O (20 KCal/mol) is much weaker than the bond strength of Fe-O (61 KCal/mol) (Ref 43) and the dissociation energy of Na-O (257 kJ/mol) is lower than the dissociation energy of Fe-O (409 kJ/mol). This leads to an increase in the values of the elastic moduli (Ref 44, 45). The elastic moduli of the glass-ceramics is larger (Ref 38) than of the parent glass. I think that heat treatment relaxes the glass structure by released some of its internal energy, the thing which causes some order and compactness structure. Therefore, different proprieties should appear, and the elastic moduli of the glass-ceramics increases.

Fig. 7
figure 7

Elastic moduli of the experimentally studied glasses with Fe2O3 by mol.%

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Fig. 8
figure 8

Elastic moduli of the theoretically studied glasses with Fe2O3 by mol.%, according to Makishima–Mackenzie Model

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Fig. 9
figure 9

Elastic moduli of the studied glass-ceramics with Fe2O3 by mol.%

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Differential Thermal Analysis

When glass is heated from room temperature, several thermal changes will take place. The best way to show these changed by DTA-thermogram. When the powder glass is heated the first thermal property is Tg, the glass transition point, the next point is Tc crystallization temperature, i.e., the glass transformation from the amorphous to the crystalline state with heat.

The thermal parameters values of the investigated glasses are presented in Fig. 10 and Table 4. Thermal parameters values are estimated by the following relationship:

$$\Delta T = \left( {T_{\text{c}} - T_{\text{g}} } \right)$$
(10)
$$H_{\text{g}} = \frac{{\Delta T}}{{T_{\text{g}} }}$$
(11)
$$S = \left( {T_{\text{p}} - T_{\text{c}} } \right) \frac{{\Delta T}}{{T_{\text{g}} }}.$$
(12)
Fig. 10
figure 10

DTA curve of the studied glasses

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Table 4 Thermal parameter and optical band gab values of the studied glasses
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It was found that all the thermal parameter values increased with the increase in the content of Fe2O3. This increasing is associated with increase in the average force constant and with the bond strength between Na-O (20 KCal/mol) is lower than the bond strength of Fe-O (61 KCal/mol) and the dissociation energy of Na-O (257 kJ/mol) is lower than the dissociation energy of Fe-O (409 kJ/mol).

XRD, TEM, and SEM Analysis for Corresponding Glass-Ceramic

Figure 11 illustrates the XRD of the selected glass-ceramics with different concentrations of Fe2O3. It is found that the XRD curves exhibit a similar profile, which indicates that the crystalline phases for all selected samples (Ref 46). The main crystalline phase could be identified as dumortierite (alumino boron silicate oxide), sodium silicate. XRD parameters of the studied glasses exhibit the grain size of all samples in nano-size. The transmission electron microscopy (TEM) micrographs of the selected samples Fig. 12a and b show the presence of crystallites in the glass matrix. The crystalline sizes can be estimated by the transmission electron microscope analysis as shown in Fig. 12a and b. The TEM confirming the data obtained by XRD. The grain size of all samples in nano-size and range between 63.9 and 165 nm. Figure 13 a and b illustrates the SEM backscattered electron images of the produced glass-ceramics. It is observed that crystalline texture contains relatively large interstitial pores, demonstrating the residual glassy matrix. The results are consistent with the XRD and TEM analysis. It was associated with a decrease in the number of non-bridging and an increase in the degree of polymerization. When the glasses were heated at their Tp, the average grain size decreased, and the morphology of the crystals changed. The crystallinity and morphology had direct effects on the mechanical and chemical properties of the glass-ceramics.

Fig. 11
figure 11

XRD curve of the prepared glass-ceramics

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Fig. 12
figure 12

(a) TEM image of G1 glass-ceramics that was dissolved in ethyl alcohol at room  °C and size of the nanoparticle. (b) TEM image of G5 glass-ceramics that was dissolved in ethyl alcohol at room  °C and size of the nanoparticle

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Fig. 13
figure 13

(a) SEM backscattered of G1 electron images of the produced glass-ceramics. (b) SEM backscattered of G5 electron images of the produced glass-ceramics

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Optical Absorption Spectra

The measured spectra of glass transmittance (T) and absorbance (A) for undoped and doped Fe2O3 glasses in 200-2700 nm spectral range are represented in Fig. 14. It was noted that the increase in Fe2O3 content shifts the absorption edge to the larger wavelengths. Also, the absorption edge for the present glasses is not sharply defined, which indicates their glass state. The glass optical band gap (Eg) may be investigated based on the following relationship.

Fig. 14
figure 14

The measured spectra of glass transmittance (T) and absorbance (A) for undoped and doped Fe2O3 glasses

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The optical absorption coefficient of the studied glasses in wavelength variety 200-2700 nm is shown in Fig. 15. The absorption coefficient (α) of the glasses can be given from the UV transmittance (T), the reflectance (R), and the thickness (d) of the glass sample according to a mentioned relation elsewhere (Ref 47, 48) as:

$$\alpha \left( \lambda \right) = \frac{1}{x} \ln \left( {\frac{1 - R}{T}} \right)$$
(13)

where x is sample thickness.

Fig. 15
figure 15

Absorption coefficient of the studied glasses

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Optical Band Gap

The optical band gap is determined by Tauc’s formula (Ref 49).

$$\alpha .h\nu = {\text{C}} \left( {h\nu - E_{{{\text{opt}} .}} } \right)^{r}$$
(14)

where Eopt is the optical band gap, C is an energy-independent constant, and the exponent r takes different values depending on the mechanism of inter-band transitions (P = 1/2 for direct and P = 2 for non-direct transitions). The absorption coefficient parameter \(\sqrt {\alpha .h\nu }\) was plotted against \(h\nu\) for all glasses understudy as shown in Fig. 16. It observed an increase in Eg values as listed in Table 1 with the increase in Fe2O3 content. This increase can be interpreted in terms of the Mott and Davies model (Ref 50). As indicated by this model, the Eg values are inversely proportional to the localized state’s width (γ). In other words, the formation of bridging oxygen BO that binds excited electrons high firmly than non-bridging oxygen increases with Fe2O3 results in the increase in the optical energy band gap. The \(E_{{{\text{opt}} .}}\) values are agreeing with that found in the literature (Ref 51,52,53,54,55,56).

Fig. 16
figure 16

Plot of (α hν)1/2 against photon energy (hν)

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The values of the index of refraction (n) at any wavelength (λ) are calculated based on the measured transmittance (T) according to the following relationship:

$$n = \frac{{\left( {1 + \left( {1 - T^{2} } \right)} \right)^{1/2} }}{T}.$$
(15)

According to the Lorentz–Lorenz equation (Ref 52), the glass density is directly proportional to the index of refraction and inversely proportional to the molar volume. Therefore, the increment of the refractive index proportional may be due to the increase in the glass densities. The studied glasses index of refraction was increased with increasing Fe2O3 as shown in Fig. 17.

Fig. 17
figure 17

The refractive index of the studied glasses

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Conclusions

The assembled glasses xFe2O3-35SiO2-35B2O3-10Al2O3-(20 − x) Na2O (0 ≤ x ≤ 1 mol.%) have been successfully fabricated via conventional melt quenching technique. The XRD analysis showed that the examined glass samples were amorphous. The density (ρ) of the glass samples increased. The ultrasonic velocities of these samples also increased as their Fe2O3 content increased, and this behavior was attributed to an increase in both their density and their cross-link density. The thermal stability values of these samples also increased as their Fe2O3 content increased, and this behavior was attributed an increase in the average force constant and to the bond strength between Na-O (20 KCal/mol) is lower than the bond strength of Fe-O (61 KCal/mol) and the dissociation energy of Na-O (257 kJ/mol) is lower than the dissociation energy of Fe-O (409 kJ/mol). The corresponding glass-ceramic was fabricated by controlling heat treatment. The glass-ceramics were tested, including mechanical properties, and investigated by XRD and TEM. The morphology of the investigated glasses was examined by SEM. The density (ρ) of the glass-ceramic samples increased. The elastic moduli of the prepared glasses and glass-ceramics was tested experimentally by measuring the ultrasonic wave velocities at 4 MHz. The values of density, ultrasound velocities, and elastic moduli of the prepared glass-ceramics are higher than those glasses. This behavior was attributed to the heat treatment that relaxes the glass structure by releasing some of its internal energy, the thing which causes some order and compactness structure. Therefore, different proprieties should appear, and the elastic moduli of the glass-ceramics increases. The optical feature spectra of the prepared samples are recorded at room temperature. The optical band gap (Eopt) increases with the increase in concentration of Fe2O3. The refractive index of the prepared samples has been estimated. The refractive index of the studied glasses increased with Fe2O3; this is due to an increase in density.