Structural dependence of crystallization in phosphorus-containing sodium aluminoborosilicate glasses

The article reports on the structural dependence of crystallization in Na₂O–Al₂O₃–B₂O₃–P₂O₅–SiO₂-based glasses over a broad compositional space. The structure of melt-quenched glasses has been investigated using ¹¹B, ²⁷Al, ²⁹Si, and ³¹P magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, while the crystallization behavior has been followed using X-ray diffraction and scanning electron microscopy combined with energy dispersive spectroscopy. In general, the integration of phosphate into the sodium aluminoborosilicate network is mainly accomplished via the formation of Al–O–P and B–O–P linkages with the possibility of formation of Si–O–P linkages playing only a minor role. In terms of crystallization, at low concentrations (≤5 mol.%), P₂O₅ promotes the crystallization of nepheline (NaAlSiO₄), while at higher concentrations (≥10 mol.%), it tends to suppress (completely or incompletely depending on the glass chemistry) the crystallization in glasses. When correlating the structure of glasses with their crystallization behavior, the MAS NMR results highlight the importance of the substitution/replacement of Si–O–Al linkages by Al–O–P, Si–O–B, and B–O–P linkages in the suppression of nepheline crystallization in glasses. The results have been discussed in the context of (1) the problem of nepheline crystallization in Hanford high-level waste glasses and (2) designing vitreous waste forms for the immobilization of phosphate-rich dehalogenated Echem salt waste.     

Novel insights into electrical transport mechanism in ionic‐polaronic glasses

Transformation of electrical transport from ionic to polaronic in glasses, which are a potential class of new cathode materials, has been investigated in four series containing WO₃/MoO₃ and Li⁺/Na⁺ ions, namely: xWO₃–(30?0.5x)Li₂O–(30?0.5x)ZnO–40P₂O₅, xWO₃–(30?0.5x)Na₂O–(30.5x)ZnO–40P₂O₅, xMoO₃–(30?0.5x)Li₂O–(30?0.5x)ZnO–40P₂O₅, and xMoO₃–(30?0.5x)Na₂O–(30?0.5x)ZnO–40P₂O₅, 0 ≤ x ≤ 60, (mol%). This study reports a detailed analysis of the role of structural modifications and its implications on the origin of electrical transport in these mixed ionic‐polaron glasses. Raman spectra show the clustering of WO₆ units by the formation of W–O–W bonds in glasses with high WO₃ content while the coexistence of MoO₄ and MoO₆ units is evidenced in glasses containing MoO₃ with no clustering of MoO₆ octahedra. Consequently, DC conductivity of tungstate glasses with either Li⁺ or Na⁺ exhibits a transition from ionic to polaronic showing a minimum at about 20‐30 mol% of WO₃ as a result of ion‐polaron interactions followed by a sharp increase for six orders of magnitude as WO₃ content increases. The formation of WO₆ clusters involved in W‐O‐W linkages for tungsten glasses plays a key role in significant increase in DC conductivity. On the other hand, DC conductivity is almost constant for glasses containing MoO₃ suggesting an independent ionic and polaronic transport pathways for glasses containing 10‐50 mol% of MoO₃.     

Transport of potassium ions in niobium phosphate glasses

The influence of Nb₂O₅ on the structure and ionic conductivity of potassium phosphate glasses was investigated in glasses with composition xNb₂O₅–(100-x)[0.45K₂O–0.55P₂O₅], x = 10–47 mol%. The Raman spectra of glasses reveal a transition from predominantly orthophosphate to predominantly niobate glass network with increasing Nb₂O₅ content. In the glass structure, niobium forms NbO₆ octahedra which are interlinked with phosphate units for the glass containing 10 mol% Nb₂O₅, but for higher Nb₂O₅ content they become mutually interconnected via Nb-O-Nb bonds. The transport of potassium ions was found to be strongly dependent on the structural characteristics of the glass network. While the mixed niobate-phosphate glass network hinders the diffusion of potassium ions by providing traps that immobilize them and/or by blocking the conduction pathways, predominantly niobate glass network exhibits a rather facilitating effect which is evidenced in the trend of DC conductivity as well as in the features of the frequency-dependent conductivity and typical hopping lengths of potassium ions.     

Structural and Optical Properties of Erbium and Ytterbium Codoped Germanoniobophosphate Glasses

A series of glasses with compositions of 20Na₂O–30Nb₂O₅–(5?y?z)Al₂O₃–30P₂O₅–(15?x)TiO₂–xGeO₂–yEr₂O₃–zYb₂O₃, where x = (0; 5; 10; 15), y = (0; 1), z = (0; 2) mol%, were investigated with respect to their structural, optical, and luminescence properties. The coordination of the germanium(IV) ion is normally reported as being mainly tetrahedral. However, results of this study suggest that the germanium(IV) ion may have an octahedral coordination and that TiO₂ is substituted. This proposition can be done mainly by ³¹P MAS‐NMR spectroscopy, which spectra show predominantly pyrophosphate chains in the different glasses, without changes in their polymerization after substitution. A similar coordination of germanium can also be identified by the photoluminescence behavior of the different codoped samples, which shows similar erbium(III) emission decay lifetimes (5 ms), and Judd–Ofelt intensity parameters. It was found that the upconversion emission process involved 1.5 photons. Regarding the thermal behavior, it is noted that the glasses containing higher proportions of GeO₂ exhibit higher thermal stability and are therefore more resistant to devitrification when compared to compositions containing more TiO₂.     

Effect of Mg2+ and fluorine on the network and highly efficient photoluminescence of Eu3+ ion in MgF2–BaO–B2O3 glasses

The glass structure and photoluminescence of new oxyfluoride glasses with the composition of xMgF₂–(66.7−2x/3)BaO–(33.3−x/3)B₂O₃ (x = 10-50 mol%) were investigated in this work. The structure of the glasses was investigated by magic-angle spinning NMR, XAS, and Raman scattering spectroscopies. It was revealed that the glasses are mainly composed of BO₃ units with a disconnected borate network consisting mainly of ortho- and pyro-borate units, and ortho-borate increases with the addition of MgF₂. The fluorine atoms are surrounded by Mg²⁺ and Ba²⁺ ions. The photoluminescence of Eu³⁺-doped samples were investigated. It was indicated that asymmetry of the Eu³⁺ site increased with the addition of MgF₂. The photoluminescence quantum yield (η) of the glasses are very high and increased with MgF₂ addition; red photoluminescence is observed with η = 82% for 10MgF₂ and η = 98% for 50MgF₂ for excitation at 393 nm.     

Effect of the Glass Structure on Emission of Rare‐Earth‐Doped Borate Glasses

A series of glasses composed of xB₂O₃–8Al₂O₃‐(90?x)Na₂O–R₂O₃ (x = 65, 70, 75, 80, 85; R = Dy³⁺, Tb³⁺, Sm³⁺) were prepared through melt‐quenching. Structural evolution was induced by varying the glass composition. Increasing the glass network former B₂O₃ enhanced the luminescence of rare‐earth ions, as observed in the emission spectra. The mechanism of the glass structural evolution was investigated by the NMR spectra analysis. The dispersant effect of the glass structure was believed to promote the better distribution of the rare‐earth ions in the matrix and reduced the concentration quenching between them. The relationship between the glass structure and its optical properties was established.     

Optimization of electrical conductivity in the Na2O-P2O5-AlF3-SO3 glass system

We report on the individual roles of charge carrier density and network modification in sodium ion conducting glasses from the Na₂O-P₂O₅-SO₃-AlF₃ (NAPFS) system. For this, a broad range of glass compositions was considered across the series of 44Na₂O/(56 – x − y)P₂O₅/xAlF₃/ySO₃, 47Na₂O/(53 − x − y)P₂O₅/xAlF₃/ySO₃, and 50Na₂O/(50 − x − y)P₂O₅/xAlF₃/ySO₃, with x = 8, 12, 16, 20 and y = 0, 5, 7, 10, 12. Impedance spectroscopy was conducted on these glasses at frequencies from 10⁻² to 10⁶ Hz and over temperatures from 50 to 250°C, and complemented by structural analyses using Raman spectroscopy and nuclear magnetic resonance data. While the trends in dc conductivity and activation energy follow that of Na₂O content (increasing from 44 to 50 mol%), substantial enhancement of conductivity (by about two orders of magnitude) and correspondingly lower activation energy were also found for constant Na₂O concentration when adjusting SO₃ or AlF₃ within specific limits of glass structure.     

New calcium‐free Na2O–Al2O3–P2O5 bioactive glasses with potential applications in bone tissue engineering

Sodium aluminophosphate glasses were evaluated for their bone repair ability. The glasses belonging to the system 45Na₂O–xAl₂O₃‐(55‐x)P₂O₅, with x = (3, 5, 7, 10 mol%) were prepared by a melt‐quenching method. We assessed the effect of Al₂O₃ content on the properties of Na₂O–Al₂O₃–P₂O₅ (NAP) glasses, which were characterized by density measurements, DSC analyses, solubility, bioactivity in simulated body fluid and cytocompatibility with MG‐63 cells. To the best of our knowledge, this is the first investigation of calcium‐free Na₂O–Al₂O₃–P₂O₅ system glasses as bioactive materials for bone tissue engineering.     

Network of Bi2O3–Al2O3–NaPO3 glasses studied by solid-state nuclear magnetic resonance spectroscopy

A detailed structural investigation of a series of phosphate laser glasses with composition xBi₂O₃–yAl₂O₃–(100 − x–y)NaPO₃ (x = 0, 10; y = 0, 5, 10, 15, 20) has been conducted using solid-state nuclear magnetic resonance (NMR) techniques and X-ray photoelectron spectroscopy (XPS). ³¹P MAS NMR spectroscopy demonstrates that the addition of Bi₂O₃ and Al₂O₃ leads to the depolymerization of the phosphorus chain in the process of Q² → Q¹ → Q⁰. The various phosphorus species (Qⁿ, n = 0, 1, 2) are identified by ³¹P single pulse, ³¹P{²⁷Al} rotational echo adiabatic passage double resonance, ³¹P{²⁷Al} J-coupling-based heteronuclear multiple-quantum coherence, and 1D refocused INADEQUATE experiments. The results of ²³Na{³¹P}, ³¹P{²³Na}, ²⁷Al{³¹P} rotational echo double resonance, and XPS consistently confirm that Na⁺, Al³⁺, and Bi³⁺ ions are all bound by phosphorus tetrahedron [PO₄]³⁻. No bond is formed between these glass modifiers. Based on the complementary evidence from previous experiments, comprehensive local structure models are developed for these Bi₂O₃–Al₂O₃–NaPO₃ glasses.     

Thermal,Structural, and Crystallization Properties of New Tantalum Alkali‐Germanate Glasses

In this work, new glass compositions were prepared in the ternary system GeO₂–K₂O–Ta₂O₅. Potassium oxide was added to reach the complete melt of the starting mixture and two composition series were investigated: the first one with a constant K₂O molar content of 10% in the ternary system (90–x)GeO₂–10K₂O–xTa₂O₅ and the second one with the same molar content of K₂O and Ta₂O₅ in the ternary system (100–2x)GeO₂–xK₂O–xTa₂O₅. Homogeneous and transparent glasses could be obtained between x = 0 and 20. X‐ray diffraction analyzes of samples with x = 25 identified orthorhombic Ta₂O₅ in the first series and an isostructure of K_3.8Ge₃Nb₅O_20.4 in the second series where it is assumed that Ta⁵⁺ ions are inserted in the Nb⁵⁺ sites. As one of our goal with these materials is related with the preparation of glass‐ceramics containing Ta₂O₅ nanocrystals, the first series has been selected for further characterizations. An increase in glass‐transition temperatures with increasing Ta₂O₅ content as well as an increase of the thermal stability from x = 0 to 10 has been identified by differential scanning calorimetry. For higher contents, crystallization events were identified. Fourier transform infrared and Raman spectroscopic characterizations allowed to point out the intermediary behavior of Ta₂O₅ in the vitreous network where TaO₆ octahedra are inserted inside the germanate network with TaO₆ clusters identified at higher Ta₂O₅ contents. Heat‐treated samples with high tantalum contents (x = 15 and 20) exhibit preferential precipitation of orthorhombic Ta₂O₅ with nanometric size, suggesting the possibility of obtaining transparent glass‐ceramics for optical applications.     

Role of MgO on the HAp forming ability in phosphate based glasses

Phosphate-based glasses 45P₂O₅–30CaO–(25 ? x)Na₂O–xMgO for different compositions of x = 0, 1, 2.5, 5 and 10 mol% were prepared using the normal melt quench technique. To study the influence of MgO on phosphate glasses, a series of experimental analyses such as ultrasonic velocities, differential thermal analysis, X-ray diffraction, energy-dispersive X-ray spectroscopy, pH measurements, Fourier transform infrared spectroscopy, scanning electron microscopy and in vitro studies were carried out in all the prepared glasses. A maxima in ultrasonic parameters at x = 2.5 mol% of MgO content and a further decrease in the same with the addition of MgO content were observed in all glasses. The observed results indicate that structural compactness of glass network took place up to 2.5 mol% of MgO (PCNM2.5), beyond which a loose packing of atoms led to structural softening in glass network. The results obtained from X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy analyses in all glasses before and after in vitro studies revealed the existence of higher HAp-forming ability in PCNM2.5 glass.     

Assessment of interatomic parameters for the reproduction of borosilicate glass structures via DFT-GIPAW calculations

Borates and borosilicates are potential candidates for the design and development of glass formulations with important industrial and technological applications. A major challenge that retards the pace of development of borate/borosilicate based glasses using predictive modeling is the lack of reliable computational models to predict the structure-property relationships in these glasses over a wide compositional space. A major hindrance in this pursuit has been the complexity of boron-oxygen bonding due to which it has been difficult to develop adequate B–O interatomic potentials. In this article, we have evaluated the performance of three B–O interatomic potential models recently developed by Bauchy et al [J. Non-Cryst. Solids, 2018, 498, 294–304], Du et al [J. Am. Ceram. Soc. https://doi.org/10.1111/jace.16082 ] and Edèn et al [Phys. Chem. Chem. Phys., 2018, 20, 8192–8209] aiming to reproduce the short-to-medium range structures of sodium borosilicate glasses in the system 25 Na₂O x B₂O₃ (75 − x) SiO₂ (x = 0-75 mol%). To evaluate the different force fields, we have computed at the density functional theory level the NMR parameters of ¹¹B, ²³Na, and ²⁹Si of the models generated with the three potentials and the simulated MAS NMR spectra compared with the experimental counterparts. It was observed that the rigid ionic models proposed by Bauchy and Du can both reliably reproduce the partitioning between BO₃ and BO₄ species of the investigated glasses, along with the local environment around sodium in the glass structure. However, they do not accurately reproduce the second coordination sphere of silicon ions and the Si–O–T (T = Si, B) and B-O-T distribution angles in the investigated compositional space which strongly affect the NMR parameters and final spectral shape. On the other hand, the core-shell parameterization model proposed by Edén underestimates the fraction of BO₄ species of the glass with composition 25Na₂O 18.4B₂O₃ 56.6SiO₂ but can accurately reproduce the shape of the ¹¹B and ²⁹Si MAS-NMR spectra of the glasses investigations due to the narrower B–O–T and Si-O-T bond angle distributions. Finally, the effect of the number of boron atoms (also distinguishing the BO₃ and BO₄ units) in the second coordination sphere of the network former cations on the NMR parameters have been evaluated.     

Effect of Niobium Oxide on the Structure and Properties of Melt‐Derived Bioactive Glasses

The effects of adding Nb₂O₅ on the physical properties and glass structure of two glass series derived from the 45S5 Bioglass^® have been studied. The multinuclear ²⁹Si, ³¹P, and ²³Na solid‐state MAS NMR spectra of the glasses, Raman spectroscopy and the determination of some physical properties have generated insight into the structure of the glasses. The ²⁹Si MAS NMR spectra suggest that Nb⁵⁺ ions create cross‐links between several oxygen sites, breaking Si–O–Si bonds to form a range of polyhedra [Nb(OM)_6?y(OSi)_y], where 1 ≤ y ≤ 5 and M = Na, Ca, or P. The Raman spectra show that the Nb–O–P bonds would occur in the terminal sites. Adding Nb₂O₅ significantly increases the density and the stability against devitrification, as indicated by ΔT(T_x ? T_g). Bioglass particle dispersions prepared by incorporating up to 1.3 mol% Nb₂O₅ by replacing P₂O₅ or up to 1.0 mol% Nb₂O₅ by replacing SiO₂ in 45S5 Bioglass^® using deionized water or solutions buffered with HEPES showed a significant increase in the pH during the early steps of the reaction, compared using the rate and magnitude during the earliest stages of BG45S5 dissolution.     

Toward hard and highly crack resistant magnesium aluminosilicate glasses and transparent glass-ceramics

High hardness and high crack resistance are usually mutually exclusive in glass materials. Through the aerodynamic levitation and laser melting technique, we prepared a series of magnesium aluminosilicate glasses with a constant MgO content, and found a striking enhancement of both hardness and crack resistance with increasing Al₂O₃. The crack resistance of the magnesium aluminosilicate glass is about five times higher than that of the binary alumina-silica glass for the similar [Al]/([Al] + [Si]) molar ratio (around 0.6). For the selected magnesium aluminosilicate glass with R = 0.32, when subjected to isothermal treatment at 1283K, we observed a further drastic enhancement of both hardness and crack resistance by extending the heating time. Based on the structural analyses, we propose an atomic-scale model to explain the mechanism of synergetic enhancement in hardness and crack resistance for the magnesium aluminosilicate glasses and glass-ceramics.     

Cation field-strength effects on ion irradiation-induced mechanical property changes of borosilicate glass structures

We examine the impact of the glass network-modifier cation field strength (CFS) on ion irradiation-induced mechanical property changes in borosilicate (BS) glasses for the ternary M₂O–B₂O₃–SiO₂ systems with M = {Na, K, Rb} and the quaternary [0.5M₍₂₎O–0.5Na₂O]–B₂O₃–SiO₂ systems with M = {Li, Na, K, Rb Mg, Ca, Sr, Ba}. ¹¹B nuclear magnetic resonance (NMR) experiments on the as-prepared BS glasses yielded the fractional population of four-coordinated B species (B^[4]) out of all {B^[3], B^[4]} groups in the glass network, along with the fraction of B^[4]–O–Si linkages out of all B^[4]–O–Si/B bonds. Both parameters correlated linearly with the (average) CFS of the M⁺ and/or {M⁽²⁾⁺, Na⁺} cations. Both the nanoindentation-derived hardness and Young's modulus values of the glasses reduced upon their irradiation by Si²⁺ ions, with the property deterioration decreasing linearly with increasing M^z+ CFS, that is, for higher M^z+⋅⋅⋅O interaction strength. The irradiation damage of the glass network also increased linearly with the fraction of B^[4]–O–Si linkages, which are the second weakest in the structure after the M^z+⋅⋅⋅O bonds. Our results underscore the advantages of employing BS glasses with high-CFS cations for enhancing the radiation resistance for nuclear waste storage.     

Enhanced photoluminescence quantum yield of Ce3+-doped aluminum–silicate glasses for scintillation application

Ce³⁺-doped 20Gd₂O₃–20Al₂O₃–60SiO₂ (GAS:xCe³⁺) glasses (x = 0.3, 0.7, 1.1, 1.5, 1.9 mol%) with Si₃N₄ as a reducing agent were prepared. The density of the glasses is around 4.2 g/cm³. With the increase in the Ce³⁺ concentration, both the photoluminescence (PL) and PL excitation peaks of GAS:xCe³⁺ glasses show a redshift because the 4f–5d energy levels of Ce³⁺ ions are narrowed. PL quantum yield and PL decay time of GAS:xCe³⁺ glasses are 28.32–50.59% and 43–64 ns, respectively. In addition, they both first increases and then decreases with the Ce³⁺ concentration increasing, reached the maximum when x = 1.1 mol%. The integrated X-ray excited luminescence (XEL) intensity of the GAS:1.1Ce³⁺ glass is 23.86% of that of Bi₄Ge₃O₁₂ (BGO) crystal, and the light yield reaches 1200 ph/MeV with an energy resolution of 22.98% at 662 keV when exposed to γ-rays. The PL and XEL thermal activation energies of GAS:xCe³⁺ glasses are independent of Ce³⁺ ions concentration. Scintillating decay time of the glasses exhibits two components consisting of nanosecond and microsecond levels, and the scintillating decay time gradually decreases with the Ce³⁺ concentration increasing. The difference between PL and scintillating decay time is discussed regarding the different luminescent mechanisms.     

Structural and Textural Modifications of Ternary Phosphate Glasses by Thermal Treatment

Phosphate-based glasses of composition xNa₂O−(45+(10−x))CaO−45P₂O₅ with different Na₂O, CaO (x = 1, 5, 10, 15, and 20 mol%), and invariable P₂O₅ (45 mol%) contents were prepared using the rapid melt quench technique. The obtained thermal data from differential thermal analysis revealed a decline in glass transition (T_g) and crystallization (T_c) temperatures of glasses against the compositional changes. The inclusion of Na₂O at the cost of CaO in the glass network led to a reduction in its thermal stability. The thermal treatment carried out on glasses helped to derive their glass-ceramic counterparts. The amorphous and crystalline features of samples were characterized using X-ray diffraction patterns. The crystalline species that emerged out of the calcium phosphate phases confirmed the dominance of Q¹ and Q² structural distributions in the investigated glass-ceramics. The obtained scanning electron micrographs and atomic force microscopic images confirmed the surface crystallization and textural modification of the samples after thermal treatment. The N₂-adsorption–desorption studies explored the reduction of porous structures due to thermal treatment on the melt-driven glass surface. The measured elastic moduli and Vicker's hardness values of the glasses showed an increase after thermal treatment, which were reduced against the inclusion of alkali content in both glass and glass-ceramics.     

Thermochemical investigation of lithium borate glasses and crystals

Lithium borate (LB) glasses and crystals with x = Li/(Li + B) = mole fraction of Li₂O of 0.2–0.5 have been synthesized by the quenching method. The thermodynamics of these materials were analyzed by high-temperature oxide melt solution calorimetry. The formation enthalpies from oxides of glasses range from −33.6 to −67.3 kJ/mol and those of crystals range from −42.1 to −77.4 kJ/mol, where compositions are given on the basis of one mole of (Li₂O + B₂O₃). The formation enthalpies of both glasses and crystals become more negative with increasing Li₂O mole fraction up to 0.5. The enthalpies of formation of glasses can be fit over the entire composition range (0 < x < 1) by a quadratic polynomial). The vitrification enthalpies were derived for x = 0.2 to 0.5 and ranged from 8.5 to 17.6 kJ/mol. The main factors controlling energetics are the strongly exothermic acid–base reaction between the network former (B₂O₃) and the network modifier (Li₂O) and the formation of tetrahedrally coordinated boron in the glasses and crystals.     

Sintering behavior,structure and dielectric properties of CuO-ZnO-MgO-B2O3 glass-ceramics for ULTCC applications

High performance ultra-low temperature co-fired ceramic (ULTCC) materials were prepared from CuO- MgO- ZnO- Al₂O₃- B₂O₃- Li₂O glass-ceramics. The sintering behaviors, crystalline phase evolution, microstructure and dielectric properties, as well as their compatibility with Ag and Al electrodes, were investigated. With the suitable substitution of MgO for ZnO, the dielectric properties of glass-ceramics were improved. It is mainly associated with the fine microstructure, highly crystallinity, and decrease in tetrahedral distortion in the crystal lattice. All the glasses completed the densification at 575–600 °C, and ZnB₄O₇ is the only crystalline phase precipitated from the glasses. Moreover, the glass-ceramic with 1 wt% MgO sintered at 575 °C for 5 h, exhibited low relative permittivity ~ 7.1 and low dielectric loss ~ 6.40 × 10^?4. And the glass-ceramic with 4 wt% MgO sintered at 600 °C for 5 h, also displayed low relative permittivity ~ 7.1 and low dielectric loss ~ 5.77 × 10^?4. Both two glasses have good sintering compatibility with silver and aluminum electrodes, which provided high potential for ULTCC application.     

Role of MgO in lowering glass transition temperature and increasing hardness of lithium silicate glass and glass-ceramics

The effect of variation of MgO (1.5, 4.5 and 7.5 mol%) content on glass structure, crystallization behavior, microstructure and mechanical properties in a Li₂O–K₂O–Na₂O–CaO–MgO–ZrO₂–Al₂O₃–P₂O₅–SiO₂ glass system has been reported here. Increased amount of MgO enhanced the participation of Al₂O₃ as a glass network former along with [SiO₄] tetrahedra, reducing the amount of non-bridging oxygen (NBO) and increasing bridging oxygen (BO) amount in glass. The increased BO in glass resulted in a polymerized glass structure which suppressed the crystallization and subsequently increased the crystallization temperature, bulk density, nano hardness, elastic modulus in the glasses as well as the corresponding glass-ceramics. MgO addition caused phase separation in higher MgO (7.5 mol%) containing glass system which resulted in larger crystals. The nano hardness (～10 GPa) and elastic modulus (～127 GPa) values were found to be on a much higher side in 7.5 mol% MgO containing glass-ceramics as compared to lower MgO containing glass-ceramics.