MAS-NMR investigations of the crystallization behaviour of lithium aluminum silicate (LAS) glasses containing P2O5 and TiO2 nucleants

Lithium aluminum silicate (LAS) glass of composition (mol%) 20.4Li₂O-4.0Al₂O₃-68.6SiO₂-3.0K₂O-2.6B₂O₃-0.5P₂O₅-0.9TiO₂ was prepared by melt quenching. The glass was then nucleated and crystallized based on differential thermal analysis (DTA) data and was characterized by ²⁹Si, ³¹P, ¹¹B and ²⁷Al MAS-NMR. XRD and ²⁹Si NMR showed that lithium metasilicate (Li₂SiO₃) is the first phase to c form followed by cristobalite (SiO₂) and lithium disilicate (Li₂Si₂O₅). ²⁹Si MAS-NMR revealed a change in the network structure already for the glasses nucleated at 550 °C. Since crystalline Li₃PO₄, as observed by ³¹P MAS-NMR, forms concurrently with the silicate phases, we conclude that crystalline Li₃PO₄ does not act as a nucleating agent for lithium silicate phases. Moreover, ³¹P NMR indicates the formation of M-PO₄ (M=B, Al or Ti) complexes. The presence of BO₃ and BO₄ structural units in all the glass/glass-ceramic samples is revealed through ¹¹B MAS-NMR. B remains in the residual glass and the crystallization of silicate phases causes a reduction in the number of alkali ions available for charge compensation. As a result, the number of trigonally coordinated B (BO₃) increases at the expense of tetrahedrally coordinated B (BO₄). The ²⁷Al MAS-NMR spectra indicate the presence of tetrahedrally coordinated Al species, which are only slightly perturbed by the crystallization.     

MAS-NMR studies of lithium aluminum silicate (LAS) glasses and glass-ceramics having different Li2O/Al2O3 ratio

Emergence of phases in lithium aluminum silicate (LAS) glasses of composition (wt%) xLi₂O-71.7SiO₂-(17.7−x)Al₂O₃-4.9K₂O-3.2B₂O₃-2.5P₂O₅ (5.1≤x≤12.6) upon heat treatment were studied. ²⁹Si, ²⁷Al, ³¹P and ¹¹B MAS-NMR were employed for structural characterization of both LAS glasses and glass-ceramics. In glass samples, Al is found in tetrahedral coordination, while P exists mainly in the form of orthophosphate units. B exists as BO₃ and BO₄ units. ²⁷Al NMR spectra show no change with crystallization, ruling out the presence of any Al containing phase. Contrary to X-ray diffraction studies carried out, ¹¹B (high field 18.8 T) and ²⁹Si NMR spectra clearly indicate the unexpected crystallization of a borosilicate phase (Li,K)BSi₂O₆, whose structure is similar to the aluminosilicate virgilite. Also, lithium disilicate (Li₂Si₂O₅), lithium metasilicate (Li₂SiO₃) and quartz (SiO₂) were identified in the ²⁹Si NMR spectra of the glass-ceramics. ³¹P NMR spectra of the glass-ceramics revealed the presence of Li₃PO₄ and a mixed phase (Li,K)₃PO₄ at low alkali concentrations.     

Structural characterisation and thermo-physical properties of glasses in the Li<Subscript>2</Subscript>O–SiO<Subscript>2</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–K<Subscript>2</Subscript>O system

This article aims to shed some light on the structure and thermo-physical properties of lithium disilicate glasses in the system Li₂O–SiO₂–Al₂O₃–K₂O. A glass with nominal composition 23Li₂O–77SiO₂ (mol%) (labelled as L₂₃S₇₇) and glasses containing Al₂O₃ and K₂O with SiO₂/Li₂O molar ratios (3.13–4.88) were produced by conventional melt-quenching technique in bulk and frit forms. The glass-ceramics (GCs) were obtained from nucleation and crystallisation of monolithic bulk glasses as well as via sintering and crystallisation of glass powder compacts. The structure of glasses as investigated by magic angle spinning-nuclear magnetic resonance (MAS-NMR) depict the role of Al₂O₃ as glass network former with four-fold coordination, i.e., Al(IV) species while silicon exists predominantly as a mixture of Q ³ and Q ⁴ (Si) structural units. The qualitative as well as quantitative crystalline phase evolution in glasses was followed by differential thermal analysis (DTA), X-ray diffraction (XRD) adjoined with Rietveld-reference intensity ratio (R.I.R.) method, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The possible correlation amongst structural features of glasses, phase composition and thermo-physical properties of GCs has been discussed.     

Transparent glass-ceramics doped with Cr(III): Low-temperature time-resolved spectra and characterization of gahnite and virgilite crystalline phases

Trivalent chromium in transparent glass-ceramics (73.6 SiO₂ :11.8 Al₂O₃:4.2 Li₂O: 7.0 ZnO: 1.6 TiO₂: 1.5 ZrO₂: 0.3 As₂O₃: 0.024 Cr₂O₃ mole%) enters mainly the gahnite phase after an equilibrium has been reached. The intermediate phase during heat treatment is of virgilite-type Li_xAl_xSi_3−xO₆. This glass-ceramic has been studied by X-ray diffraction and time-resolved spectroscopy at low temperatures under laser excitation     

Antimony and silicon environments in antimony silicate glasses

Antimony silicate glasses, of general formula xSb₂O₃·(1−x)SiO₂ (0.1≤x≤0.78), have been prepared by melt-quenching and their structures studied using ²⁹Si MAS NMR spectroscopy, ¹²¹Sb Mössbauer spectroscopy and Raman spectroscopy. Oxidation during melting gives rise to Sb⁵⁺ in concentrations, which increase linearly with x to give a value of ∼10% when x=0.78. ¹²¹Sb Mössbauer spectra show Mössbauer shifts and quadrupole splittings consistent with Sb³⁺ in a [:SbO₃] trigonal pyramid, similar to that in crystalline Sb₂O₃. A broad band in the Raman spectrum at ∼410 cm⁻¹ is due to the vibrations of such a unit. The dependence of the silicon Qⁿ speciation on x can be interpreted by the formation of Sb-O-Sb links possibly to form rings of 4 [:SbO₃] units such as are found in valentinite.     

Solid-state Al and Si NMR characterization of hydrates formed in calcium aluminate-silica fume mixtures

Partially deuterated Ca₃Al₂(SiO₄)_y(OH)_12−4y-Al(OH)₃ mixtures, prepared by hydration of Ca₃Al₂O₆ (C₃A), Ca₁₂Al₁₄O₃₃ (C₁₂A₇) and CaAl₂O₄ (CA) phases in the presence of silica fume, have been characterized by ²⁹Si and ²⁷Al magic-angle spinning-nuclear magnetic resonance (MAS-NMR) spectroscopies. NMR spectroscopy was used to characterize anhydrous and fully hydrated samples. In hydrated compounds, Ca₃Al₂(OH)₁₂ and Al(OH)₃ phases were detected. From the quantitative analysis of ²⁷Al NMR signals, the Al(OH)₃/Ca₃Al₂(OH)₁₂ ratio was deduced. The incorporation of Si into the katoite structure, Ca₃Al₂(SiO₄)_3−x(OH)_4x, was followed by ²⁷Al and ²⁹Si NMR spectroscopies. Si/OH ratios were determined from the quantitative analysis of ²⁷Al MAS-NMR components associated with Al(OH)₆ and Al(OSi)(OH)₅ environments. The ²⁹Si NMR spectroscopy was also used to quantify the unreacted silica and amorphous calcium aluminosilicate hydrates formed, C-S-H and C-A-S-H for short. From ²⁹Si NMR spectra, the amount of Si incorporated into different phases was estimated. Si and Al concentrations, deduced by NMR, transmission electron microscopy, energy dispersive spectrometry, and Rietveld analysis of both X-ray and neutron data, indicate that only a part of available Si is incorporated in katoite structures.     

Structural effects of Zn+2/Mg+2 ratios on crystallization characteristics and microstructure of fluorophlogopite mica-containing glass-ceramics

We report the effect of Mg⁺² substitution (by Zn⁺²) on crystallization kinetics, microstructure, thermal and mechanical properties of boroaluminosilicate glass. Zn²⁺ was selected for Mg²⁺ on the basis of similar ionic radius in six coordination system (Mg²⁺∼0.72 Å, Zn²⁺∼0.75 Å). The melt-quenched glasses with SiO₂–(1 − x) MgO–Al₂O₃–K₂O–B₂O₃–MgF₂ (BPAS)/x ZnO system, have been investigated to establish the effect of Zn⁺²/Mg⁺² ratios. It is found that the density of BPAS glass without zinc content is 2.52 g/cm³ and increased linearly on substitution of Mg²⁺ by 5–32 mol% ZnO. T_g and T_d of BPAS glass initially increased on adding 5 mol% ZnO and then decreased on further addition. From DSC study, it is found that the crystallization exotherm changes significantly in the temperature range 750–1000 °C, where different crystalline phases are formed, and the activation energy of crystallization (E_C) varies in the range of 254–388 kJ/mol. The crystalline phases formed in opaque BPAS glass-ceramic, derived by controlled heat treatment at 800 and 1050 °C (4 h), are identified as fluorophlogopite [KMg₃(AlSi₃O₁₀)F₂] mica and willemite (Zn₂SiO₄) by XRD technique, and confirmed by FTIR spectroscopy. The change of crystallization phenomena varying Zn⁺²/Mg⁺² ratios correspond to significant microstructural change. A wide range of thermal expansion (CTE) values are obtained for the BPAS glasses and corresponding glass-ceramics. CTE (50–500 °C) of BPAS glass without zinc content is 7.76 × 10⁻⁶/K, and decreased sequentially on increasing Zn⁺²/Mg⁺² ratio. The density of glass-ceramics after heating at 800 and 1050 °C increased linearly with increasing Zn⁺² substitution for Mg⁺². Microhardness of the BPAS glasses is in the range of 4.26–6.15 GPa and found to be increased to 4.58–6.78 GPa after crystallized at 1050 °C.     

湿化学法制备的KTiOPO4@SiO2玻璃陶瓷纳米结构和透明性

用湿化学法合成了25KTiOPO4-75SiO2透明纳米玻璃陶瓷。采用X射线衍射、场发射扫描电子显微镜和二次谐波发生对玻璃陶瓷物相及纳米结构进行了分析。透明凝胶块经过热处理后,从SiO2基玻璃中析出了粒径为~30 nm的KTiOPO4纳米晶体,形成了透明KTiOPO4@SiO2纳米玻璃陶瓷;凝胶粒子的烧结致密化消除了大量不规则介孔,但形成了少量30 nm的球状孔;这种相对致密的玻璃陶瓷在可见光波段的光学透射率为64%左右。根据纳米结构数据,利用瑞利散射模型分析了纳米结构对玻璃陶瓷透明性的影响,结果表明,KTiOPO4晶体与SiO2玻璃相折射率之差是降低致密纳米玻璃陶瓷透明性的主要因素。     

Calcium aluminates hydration in presence of amorphous SiO2 at temperatures below 90 °C

The hydration behaviour of Ca₃Al₂O₆, Ca₁₂Al₁₄O₃₃ and CaAl₂O₄ with added amorphous silica at 40, 65 and 90 °C has been studied for periods ranging from 1 to 31 days. In hydrated samples crystalline phases like katoite (Ca₃Al₂(SiO₄)_3−x(OH)_4x) and gibbsite, Al(OH)₃, were identified, likewise amorphous phases like Al(OH)_x, calcium silicate hydrates, C-S-H, and calcium aluminosilicate hydrates, C-S-A-H, were identified. The stoichiometry of Ca₃Al₂(SiO₄)_3−x(OH)_4x (0?3−x?0.334), which was the main crystalline product, was established by Rietveld refinement of X-ray and neutron diffraction data and by transmission electron microscopy.     

Er-doped PbF2: Comparison between nanocrystals in glass-ceramics and bulk single crystals

An appropriate annealing of a GeO₂-PbO-PbF₂:ErF₃ glass leads to the formation of a glass-ceramic, composed of Pb_1−xEr_xF_2+x nanosized crystallites dispersed throughout an amorphous oxide matrix. These nanocrystallites are compared to Er³⁺-doped PbF₂ bulk single crystals. The influence of the annealing temperature on the glass-ceramics characteristics is thoroughly investigated. For several glass-ceramics resulting from different heat treatments, the quantity of crystallized PbF₂, as well as the segregation of Er³⁺ ions into the crystallites, has been studied through two methods: first, the study of the crystallographic characteristics and second, the evolution of the optical properties. It was evidenced that, for a heat treatment over 365 °C, the whole PbF₂:Er has completely crystallized and that the segregation of Er³⁺ ions into the crystallites was total. Strong interactions between Er³⁺ ions occur in the Pb_1−xEr_xF_2+x single and nanocrystals, promoting cross-relaxation processes, under 488-nm excitation, and favouring the 660- (red) and 810-nm emissions at the expense of the 550-nm (green) one.     

Electrochemical performance of novel Li<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> glass-ceramic nanocomposites as electrodes for energy storage devices

The novel Li₃V₂(PO₄)₃ glass-ceramic nanocomposites were synthesized and investigated as electrodes for energy storage devices. They were fabricated by heat treatment (HT) of 37.5Li₂O–25V₂O₅–37.5P₂O₅?mol% glass at 450 °C for different times in the air. XRD, SEM, and electrochemical methods were used to study the effect of HT time on the nanostructure and electrochemical performance for Li₃V₂(PO₄)₃ glass-ceramic nanocomposites electrodes. XRD patterns showed forming Li₃V₂(PO₄)₃ NASICON type with monoclinic structure. The crystalline sizes were found to be in the range of 32–56 nm. SEM morphologies exhibited non-uniform grains and changed with variation of HT time. The electrochemical performance of Li₃V₂(PO₄)₃ glass-ceramic nanocomposites was investigated by using galvanostatic charge/discharge methods, cyclic voltammetry, and electrochemical impedance spectroscopy in 1 M H₂SO₄ aqueous electrolyte. The glass-ceramic nanocomposites annealed for 4 h, which had a lower crystalline size, exhibited the best electrochemical performance with a specific capacity of 116.4 F g^?1 at 0.5 A g^?1. Small crystalline size supported the lithium ion mobility in the electrode by decreasing the ion diffusion pathway. Therefore, the Li₃V₂(PO₄)₃ glass-ceramic nanocomposites can be promising candidates for large-scale industrial applications in high-performance energy storage devices.     

Vibrational and 29Si NMR spectroscopies of soluble silicate oligomers

Vibrational spectroscopy has been used to correlate the features of silicate solution spectra with ²⁹Si NMR spectra, as a function of SiO₂:Na₂O ratio and SiO₂ concentration. Assignments of infrared and Raman component bands have been made for different anion types and are consistent with results reported for crystalline silicates and silicate glasses. The extent of depolymerization of larger anions has been found to differ, depending on both the degree of dilution and alkalinity. The relative amounts of polymeric (Q⁴) silica and larger three dimensional (Q³_4R) anions are greater for the more siliceous solutions (3.3 and 2.95 ratio) at high concentrations. These large anions continue to be major contributors to the anion distribution even at 15 to 50 fold dilution. In the case of more alkaline solutions, especially below 2.5 ratio, the relative contribution of the large anions to the distribution drops rapidly, even with 2 or 3 fold dilution. At low concentrations, in very alkaline solutions, the anion distribution is mainly monomer, dimer and cyclic trimer. Vibrational spectroscopies show great promise for observing changes in anion distribution on a much shorter time scale than is possible with ²⁹Si NMR and can be useful for following reactions involving silicate solutions.     

Glass-ceramic nanocomposites in the [(1 − x)PbO–xBaO]–Na2O–Nb2O5–SiO2 system: Crystallization and dielectric performance

The crystallization process, microstructure and dielectric properties of [(1 − x)PbO–xBaO]–Na₂O–Nb₂O₅–SiO₂ (PBNNS) (0 ≤ x ≤ 1) glass-ceramics prepared by controlled crystallization were investigated. The crystallization strategies for acquiring nano-crystallized PBNNS glass-ceramics were monitored by differential thermal analysis (DTA). X-ray diffraction (XRD) analysis revealed a major crystal phase transition in PBNNS glass matrix as the crystallization temperature increased. At low temperatures (700–750 °C), the major crystal phases precipitating in the glass matrix are identified as Pb₂Nb₂O₇ for x = 0, Ba₂NaNb₅O₁₅ for x = 1 and their solid solution for 0.2 ≤ x ≤ 0.8; while at higher temperatures (≥850 °C), heat treatment produces different crystalline phases, PbNb₂O₆ and NaNbO₃ for x = 0, Ba₂NaNb₅O₁₅ and NaNbO₃ for x = 1, and the solid solution of these three phases for 0.2 ≤ x ≤ 0.8. Corresponding to the result of phase transition, microstructural observation proves increasing crystallite sizes with increasing temperature of heat treatment. At different crystallization temperatures, the dielectric properties of the [(1 − x)PbO–xBaO]–Na₂O–Nb₂O₅–SiO₂ glass-ceramics show a strong dependence on the chemical composition x. At low temperatures (700–750 °C), a maximum of the dielectric constant of the PBNNS glass-ceramic is found for the composition x = 0.6; while at higher crystallization temperatures (≥850 °C), the dielectric constants of all samples (0 ≤ x ≤ 1) exhibit decreasing values with increasing x.     

Sol-Gel Processing and Luminescent Properties of Rare-Earth Oxyfluoride Materials

Luminescent rare-earth oxyfluoride materials were prepared by a sol-gel method using trifluoroacetic acid as a fluorine source. Crystalline (La, Eu)OF powders and thin films were obtained by heating gels at typically 600–800°C. Transparent SiO₂-LaOF glass-ceramic thin films were also prepared by mixing the trifluoroacetate sols and silica sols, spin-coating on silica glass substrates and heating at temperatures 600–900°C. Eu³⁺ ions doped in the oxyfluoride materials exhibited a strong red ⁵D₀ ⁷F₂ emission (611 nm) by a charge-transfer (O^2–-Eu³⁺) excitation with ultra-violet radiation (265 nm). It was strongly suggested that the Eu³⁺ activators were preferentially incorporated into the crystalline LaOF phase in the SiO₂-LaOF glass-ceramics.     

Structural investigation of sol–gel derived SiO2–GeO2 noncrystalline and nanocomposite materials

Noncrystalline and nanocomposite materials of (1?x)SiO₂·xGeO₂ system, with Si:Ge ratio from 8:1 to 2:1 (x?=?0.111; 0.142; 0.2; 0.333), initially obtained by sol?Cgel method, were characterized by thermal analyses, X-ray diffraction, nuclear magnetic resonance and Raman spectroscopy. According to DTA and XRD results, the noncrystalline state of the as-prepared samples is stable up to 1,000?°C and only after 30?min heat treatment at 1,200?°C the samples become partial crystalline, due to development of cristobalite and quartz nanocrystals. Solid-state ²⁹Si MAS-NMR was employed in order to characterize the local structure around silicon as a function of composition and thermal history of the samples. The NMR data indicate the presence of Q², Q³ and Q⁴ units in all samples. The fraction of the highly interconnected SiO₄ tetrahedra increases both with germanium content and with annealing temperature. The Raman spectroscopy results evidence structural changes related to silicon- and germanium-oxygen units but also to their interconnection, that depend on Si:Ge ratio and annealing temperature.     

Effect of alumina concentration on thermal and structural properties of mas glass and glass-ceramics

Magnesium aluminum silicate (MAS) glass samples with different concentrations of alumina (7.58 to 14.71 mol%) were prepared by melt and quench-technique. Total Mg content in the form of MgF₂+MgO was kept constant at 25 mol%. MAS glass was converted into glass-ceramics by controlled heat treatment at around 950°C. Crystalline phases present in different samples were identified by powder X-ray diffraction technique. Dilatometry technique was used to measure the thermal expansion coefficient and glass transition temperature. Scanning electron microscopy (SEM) was employed to study the microstructure of the glass-ceramic sample. It is seen from X-ray diffraction studies that at low Al₂O₃ concentrations (up to 10.5 mol%) both MgSiO₃ and fluorophlogopite phases are present and at higher Al₂O₃ concentrations of 12.3 and 14.7 mol%, fluorophlogopite and magnesium silicate (Mg₂SiO₄), respectively are found as major crystalline phases. The average thermal expansion co-efficient (_avg) of the glass samples decreases systematically from 9.8 to 5.5·10^–6 °C^–1 and the glass transition temperature (T g) increases from 610.1 to 675°C with increase in alumina content. However, in glass-ceramic samples the _avg varies in somewhat complex manner from 6.8 to 7.9·10^–6 °C^–1 with variation of Al₂O₃ content. This was thought to be due to the presence of different crystalline phases, their relative concentration and microstructure.Authors wish to thank Dr V. C. Sahni, Director Physics Group and Dr J. V. Yakhmi, Head TPPED, BARC for encouragement and support to the work. They would like to thank Dr S. K. Kulshreshtha for many useful discussions. Technical assistance from Shri B. B. Sawant, Mrs Shobha Manikandan, Mr Rakesh Kumar and Shri P. A. Wagh is gratefully acknowledged. One of authors (BIS) would like to thank BRNS-DAE for awarding him KSKRA fellowship.     

Study of the cation distributions in Eu doped Sr2Y8(SiO4)6O2 by X-ray diffraction and photoluminescent spectra

The crystal structure and photoluminescent properties of europium doped silicate Sr₂Y₈(SiO₄)₆O₂:Eu³⁺ are reported. The Sr₂Y_8−xEu_x(SiO₄)₆O₂ compounds have typical apatite crystal structures with the P6₃/m space group. The distributions of Eu³⁺ between the two crystallographic sites 4f and 6h in the apatite structure are investigated by the powder X-ray diffraction and Rietveld refinement. Results show that Eu³⁺ ions only occupy the 4f sites when the Eu doping concentration is low (x=0-0.5 in Sr₂Y_8−xEu_x(SiO₄)₆O₂). However, in higher concentrations, Eu³⁺ ions begin to enter the 6h sites as well. The distributions of the Eu³⁺ are also reflected in photoluminescent spectra. The CIE coordinates for Sr₂Y₆Eu₂(SiO₄)₆O₂ are (0.63, 0.37), which is close to the pure red color.     

Crystallization of spodumene-diopside in the las glass ceramics with CaO and MgO addition

Crystallization, morphology and mechanical properties of a spodumene-diopside glass ceramics with adding different amount of CaO and MgO in Li₂O-Al₂O₃-2SiO₂ were investigated. With CaO and MgO addition, the crystallization temperature (T _p) decreased, the value of Avrami constant (n) decreased from 3.2±0.3 to 1.4±0.2, the activation energy (E) increased from 299±3 kJ mol⁻¹ to 537±5 kJ mol⁻¹. The crystalline phases precipitated were h-quartz solid solution, β-spodumene and diopside. The mechanism of crystallization of the glass ceramics changed from bulk crystallization to surface crystallization. The grain sizes and thermal expansion coefficients increased while flexural strength and fracture toughness of the glass-ceramics increased first, and then decreased. The mechanical properties were correlated with crystallization and morphology of glass ceramics.     

Crystal structure, phase relations and electrochemical properties of monoclinic Li2MnSiO4

Phase relations in the MnO-SiO₂-Li₄SiO₄ subsystem have been investigated by X-ray diffraction after solid-state reactions in hydrogen at 950-1150 °C. Both cation-deficient and cation-excess solid solutions Li_2+2xMn_1−xSiO₄ (−0.2?x?0.2) based on Li₂MnSiO₄ have been found. According to Rietveld analysis, Li₂MnSiO₄ (monoclinic, P2₁/n, a=6.3368(1), b=10.9146(2), c=5.0730(1) Å, β=90.987(1)°) is isostructural with γ_II-Li₂ZnSiO₄ and low-temperature Li₂MgSiO₄. All components are in tetrahedral environment, (MnSiO₄)²⁻ framework is built of four-, six- and eight-member rings of tetrahedra. Testing Li₂MnSiO₄ in an electrochemical cell showed that only 4% Li could be extracted between 3.5 and 5 V against Li metal. These results are discussed in comparison with those for recently reported orthorhombic layered Li₂MnSiO₄ and other tetrahedral Li₂MXO₄ phases.     

Influence of SiO2 on the structure and optical properties of lithium bismuth silicate glasses

Bismuth silicate glasses containing lithium oxide with composition 20Li₂O·(80 − x)Bi₂O₃·xSiO₂ (5 ? x ? 70 mol%) have been prepared by melt-quench technique. Density (D), molar volume (V_M) and glass transition temperature (T_g) for all the glass samples have been measured. FTIR spectroscopy has been employed to investigate the structure of these glasses in order to obtain information about the competitive role of Bi₂O₃ and SiO₂ in the formation of glass network. The increase of SiO₂ content in the glass matrix results in increasing the Si-O-Si bond angle and hence the ionicity of Si-O bond increases with decrease in Bi₂O₃/SiO₂ ratio. The optical transmittance spectra of all the glasses have been recorded in the wavelength range 200-3300 nm. The values of optical band gap (E_g) have been determined from the cutoff wavelength of these glasses. The average electronic polarizability of oxide ion () and the optical basicity (Λ_th) have been estimated from the calculated values of the E_g and were found to be dependent directly on Bi₂O₃/SiO₂ ratio. The variation in different physical parameters such as D, V_M and T_g and optical parameters; viz., E_g, , Λ_th with Bi₂O₃/SiO₂ ratio have been analyzed and discussed in terms of change in the glass structure.