Optical Properties of SiO2 – TiO2 – La2O3 – Na2O – Y2O3 Glasses and A Novel Process of Preparing the Parent Glass-Ceramics

Quaternary glasses with the composition 50SiO2 – 25TiO2 – 5La2O3 – (20-x) Na2O – xY2O3 where x : (0 ≤ x ≥ 10) were synthesized using the melt-quench technique. XRD examined the nature of prepared glasses. UV-spectroscopic of investigated glass system studied at room temperature. Both optical bandgap and refractive index of the present glass have been increased. The polarizability and basicity were determined. Thermal parameter values increased as Y2O3 increased. Under controlling heat, the glass-ceramic were prepared and confirmed using XRD. Glass-ceramics are examined using SEM to evaluate a microstructure. Ultrasonic velocities and elastic-moduli of glass-ceramic samples are increased because of the increase in internal energy. The role of Y2O3 modifier in the glass system is clearly demonstrated. Y2O3 also works as an excellent nucleating agent that can induce crystallizations, supporting in the creation of the sub-phase of glass-ceramics.


Introduction
Glasses containing transition metals oxides attract the attention of several researchers for excellent infrared transmission compared with the conventional glasses. It makes an ideal candidate for various applications such as infrared transmission components, ultra-fast optical switches, and photonic devices [1][2][3]. Silicate glasses containing transition metal ions exhibit unique, versatile structural properties in physical and spectral (optical & FTIR) studies, and light activated bioactive glass [4][5][6][7][8][9][10][11]. In recent years, the studies on transition metal ions containing glasses have been increased due to their admirable improvements in semiconducting properties and optoelectronic electronic devices. The abundance of multiple valance states of transition metal ions which arises from unfilled d-orbitals made them a potential candidate for extending their applicability in electrical memory switching, photo-conducting, solid-state batteries, and electronic devices [12]. Transition metal ions containing glass are considered semiconducting substances. Nowadays The glasses are considered potential applicants for electronic, mechanical, and optical [12].
TiO2 containing glasses show remarkable properties like low phonon frequency, highdielectric, non-linear optical, electric, and magnetic. Under these characteristics glass doped TiO 2 has extend applications in the field of optics, photonics, optoelectronics, and telecommunication devices. In glasses, usually TiO 2 , are intermediate, crystallizing agents and it may be observed in the Ti 4+ and involved in the structural units of TiO 4 , TiO 6 and TiO 5 [13][14][15][16][17][18].
The incorporation of Y 2 O3 into sodium-silicate glasses causes the replacement of weak Si-O-Na bonds with strong Si-O-Y bonds lead to enhances the thermal, optical & chemical stability of host glasses. The introduction of Y 2 O 3 into the glass network enhanced the optical and physical properties of the glass [19]. Glasses containing rare-earth ions have several optical and photonic applications available [20][21][22][23][24][25][26][27][28]. It is highly possible for UV optics and solid-state batteries applications because of the good ionic conductivity of these glasses [20][21][22][23][24][25][26][27][28]. Considering the importance of sodium titanium silicate glasses in scientific and technological, characteristics like ionic conductivity in power generation glasses modified with various oxides are strongly required [28,29]. In contrast, the incorporation of transitional or rare earth oxides into sodium titanium silicate glass structures are enhanced optical, electrical, thermal, mechanical and radiation protection characteristics [30][31][32][33]. Glasses containing rare-earth ions have attracted a great deal of interest because of their benefits [34][35][36][37][38][39]. Intermediate oxides such as Y 2 O 3 can act either as a glass modifier or former, depending on their concentration in the glass matrix. Y 2 O 3 enhances the host glass matrix's physical structure and mechanical strength. [40][41][42][43][44][45][46]. The existence of Y 2 O 3 enhances the capacity to form glass and reduces devitrification. The existence of TiO 2 and Y 2 O 3 impacts UVspectroscopic in glass systems. These glasses possess lower photon energy and higher refractive index than other glasses. Scientifically and technologically, the recent innovation of titanium silicate glasses containing Y 2 O 3 and La 2 O 3 is very significant ( Table 1).
In the 1950s, Stookey and Kingery [47] discovered the first glass-ceramic that could be manufactured industrially by adding the nucleating agent TiO 2 to control the devitrification of glass. Even at the end of the nineteenth century, Mc. Millan used crystallization [48]. After Stookey's discovery of the controlled nucleation and crystallization of glass-ceramics, several studies on sintered glass-ceramics were published [49,50]. Glass-ceramics are polycrystalline materials formed by heat treatment of glasses of appropriate compositions. Crystallization is an important topic in glass science as well as in glass technology. The crystallization behavior and the final properties of glass ceramics parts are mainly affected by the configuration of the parental glass, the nucleating system, and the crystallization conditions. In comparison to those of the parent glass, the mechanical properties of glass-ceramics are better. Glass-ceramics can also, exert other unusual characteristics that are valuable for purposes, as shown by the incredibly small thermal expansion coefficient, which is therefore acceptable for thermal shock-resistant implementations. The goal of our article is preparing of lanthanum titanium silicate glasses containing yttrium and investigating their structural and optical properties.

Experimental Processes and Techniques
The glasses in this study were synthesized from 50SiO 2 -25TiO 2 -5La 2 O 3 -(20-x) Na 2 O -xY 2 O 3 in platinum crucible using the melt-quench technique method where x : (0 ≤ x ≥ 10) mol %. The starting materials are SiO 2 , Na 2 CO 3 , La 2 O 3, Y 2 O 3 and TiO 2 with high purity. All chemicals used for the glass preparation obtained from Sigma-Aldrich. The starting materials were mixed by grinding the mixture repeatedly to obtain a fine powder. Firstly, the starting materials have been heated to 450°C for 4 h to eliminate H 2 O, and CO 2 . The temperature has been raised to 1200°C for 30 min. The glasses were annealed at 450°C for 2 h to relieve the internal stresses and allowed to cool gradually to room temperature. The weight losses were found to be less than 1%.
The amorphous state of the glasses and glass-ceramics were checked using X-ray diffraction. A Philips X-ray diffractometer PW/1710 with Ni-filtered Cu-Kα radiation (λ = 1.542 Å) powered at 40 kV and 30 mA was used. UVspectroscopic of investigated glass system is studied by spectrophotometer (type JASCO V-670). Archimedes principle describes the density as the following relation: ρ ¼ ρ 0 the weight of samples in air and liquid is C and C1 respectively, the density of glass-ceramic sample is ρ, and toluene is ρ 0 (0.865) g/cm 3 . DTA-50 (type Shimadzu) used for the thermal investigation. By heating the specimen at specified temperatures on two steps, first, at 500°C, the glassceramics are produced, the sconed is 1 h at T c°C , the crystal growth. A pulse-echo method is used to study mechanical measurements for glass-ceramics by (KARL DEUTSCH Echograph model-1085). The model (JEM-100 CX 11 JAPAN), a scanning microscope (SEM), has been used to examine the morphology of investigated glass-ceramic. Figure 1. shows the X-ray results of the studied glasses. These diffractograms show no discrete lines, no sharp peaks, and indicate that glass samples have a high degree of glassy state. The slight shift in the hump at (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) 2θ°values with respect to Y 2 O 3 concentration can be related to the decrease in the bond length and to the higher coordination number with oxygens.

UV-Visible Absorption Spectra
UV-Vis-NIR absorption spectroscopy is a completely beneficial approach to characterize the optical of different substances which include thin films, filters, pigments, glass, and  Figure 2 exemplifies the absorbance (A) and transmittance (T) of glass samples. Figure 3 exemplifies the reflectance (R) of these glasses. There have indications of increasing the absorption coefficient as Fig. 4. Therefore, Y 2 O 3 is accounted as BO development [51]. The absorption coefficient ∝was calculated by: Where x is sample thickness.

Optical Band Gap E opt
Absorption spectra of glasses in the ultraviolet and visible regions have been used to calculate optical band gap.
Optical band gap is determined by (α. hν .where E opt is optical band gap, B is an energy independent constant and hν is photon energy. By plotting the (α. hν) 1/2 versus hν as Fig. 5. The intercept of ffiffiffiffiffiffiffiffi αhν p versus hν at ffiffiffiffiffiffiffiffi αhν p ¼ 0 denoted the value of E opt . It was noted with increasing Y 2 O 3 content the energy gap increases as in Table 2. This increase can be explained as oxygen bridges (BO) are generated that bind energized electrons more strongly than non-bridging oxygen (NBO). Also, this increasing of E opt may be due to change in composition of glass matrix and increase the interconnection.

Refractive Index (N)
According to the theory of reflectivity of light, the refractive index (n) values obtained as a function of the reflectance (R) and the extinction coefficient (k) as:
The molar refractivity depends on E opt. R m ¼ Vm and molar polarizability (∝ m ). Reflection . These values of (R m ) (∝ m ) and (R L ) decrease with yttrium because of the decrease in the molar volume are presented in Table 2. The criterion for metallization is predict- Vm , the metallization value rises with Y +3 . The electronegativity (χ) is predicted as χ = 0.2688E opt. . where E opt. bandgap. Thus, with Y +3 increasing, the electronegativity (χ) values increase. The electron polarizability is predicted as,∝°= − 0.9 χ + 3.5 and optical basicity ∧ = − 0.5χ + 1.7. ∝°and ∧ have the inverse trend of (χ) thus, with Y +3 increase   Table 2 shows the variation of these values.

Thermal Analysis
DTA-thermograms are the best way to show thermal properties. The first thermal attribute is the transition temperature of samples T g , while the following thermal property consists of T c and T p crystallization and peak temperatures. DTAthermograms of glasses are presented in Fig. 10. It is observed that these parameters have been increased as the Y 2 O 3 increases. This is related to increase in the connection of the glass structure. According to these parameters, the glassceramics have been prepared. The estimated thermal stability values as: ΔT = (Tc − Tg), Hg ¼ ΔT Tg ,and S ¼ Tp−Tc ð Þ ΔT Tg are listed in Table 3. [59]. This behavior is linked to the modification of the coordination number with increasing Y 2 O 3 , the growth in average constant force and cross-link density. As Y 2 O 3 increases at expense of Na 2 O, the molar volume decreases and the density increases, making the glass structure more compact.

XRD and SEM Analysis for Consistent Ceramic-Glass
Glass-ceramics have been investigated using XRD for further analysis, as seen in the Fig. 11. The XRD pattern of G1 and G6 are similar, as noticeable from the Fig. 11, excluding that diffraction peaks are stronger. High transparency, uniform color, and good chemical and mechanical properties were    The microcracks had been easily obtained during the recrystallization process based on differences in the coefficients of thermal expansion between the phases of yttrium and the impeccable standards phase, helping to make the glass-ceramic much harder. Glass-ceramics had been examined using SEM, as seen in Figs, 12a and b to evaluate a microstructure. The size of the crystal is listed in Tables 4 and 5. SEM photograph of selected glass-ceramic samples. It is indicated that uniform distributions in the glass composition. Figure 12 show the micrographically (G1). It is indicated a nearly unchanging on the surface. Lanthanum Titanium Silicate was crystallized in occasional crystalline texture that includes comparatively large interstitial pores reflecting the remaining glassy matrix. Figure 13 illustrations the micrographically (G6). It is indicated that uniform distributions in the glass composition [60]. With the increase of Y 2 O 3 content, the possibility of crystallization is increased, and a glass sub-phase has been created to increase the internal energy. To determine elastic-moduli as,

Mechanical Properties of Glass-Ceramics
G: Elastic-moduli of glassceramic have been estimated and represented in Fig. 15 and Table 6. It indicated that, these moduli increasing with the Poisson's ratio is projected as 1þσ ð Þ , Thermal Expansion (α P ), α P¼23:2 v L −0:57457 ð Þ and acoustic impedance (Z). All these parameters are shown in Table 6 and they increased as the yttrium content increase because of the role of a Y 2 O 3 modifier in the glass system is clearly demonstrated.  Fig. 11 The XRD of the selected glass-ceramics

Conclusions
Quaternary glasses with the composition of 50SiO 2 -25TiO 2 -5La 2 O 3 -(20-x) Na 2 O -xY 2 O 3 have been manufactured using conventional melt-quenching methods. The optical, thermal, crystallization, and mechanical variables have been examined for these glasses. XRD measurements established the amorphous nature of glasses. Optical absorption was quantified to understand the optical characteristics of the prepared glasses. With increasing Y 2 O 3 content the energy gap increases. This grow can be explained as oxygen bridges (BO) are generated that bind energized electrons more strongly than non-bridging oxygen (NBO). Refractive index of investigated glasses are increases as density increase. Molar polarization, polarizability, and optical basicity of these glasses having the  Table 6 values of sound velocities (v L and v T ), elastic moduli, Poisson's ratio, micro hardness, acoustic impedance (Z) and thermal expansion coefficient (α P ), of the studied glass-ceramics increased. Metallization of these glasses were enhanced because of increment of TiO 2 . Thermal stability of these glasses was increased as the Y 2 O 3 increases. These increases related to increase in the connection of the glass structure. Under controlling heat, the glass-ceramic was prepared and investigated by XRD, SEM, and mechanical properties. XRD results showed all the expected phases due to the crystallization process. SEM photograph of selected glass-ceramic samples indicated that uniform distributions in the glass composition. Ultrasonic velocities and elastic-modules of glass-ceramic samples are increased because of increase in internal energy. Funding Statement There are currently no Funding Sources in the list.
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