Calcium Borosilicate Glass Research Articles

Weakening the silicate network through six-coordinated magnesium to achieve a high degree of crystallization of β-CaSiO3 in calcium borosilicate glass ceramics for 5G application

β-CaSiO3 with a low dielectric constant and low dielectric loss is one of the decisive components of commercial calcium borosilicate (CBS) low-temperature co-fired ceramic substrate. However, achieving a high degree of crystallization of β-CaSiO3 is difficult in CBS glass ceramics because of the competitive multiphase crystallization during sintering. We have shown that six-coordinated magnesium can be used to weaken the silicate network to achieve a high degree of crystallization of β-CaSiO3 in CBS glass ceramics. The appropriate MgO content to ensure a large amount of MgO6 production gradually destroys the [SiO4] tetrahedral network as the temperature increases, resulting in a β-CaSiO3 content of 76.2 vol%, when the MgO content is 2.71 mol%. The resulting material has the lowest dielectric constant (4.95@15 GHz) and dielectric loss (8 × 10−4@15 GHz), and the best three-point bend strength (77.43 MPa). Our work provides an effective method of changing the crystallization by modifying the glass network in silicate-based glass ceramics with a low dielectric constant.

Impacts of substitution of Fe2O3 for SiO2 on structure and properties of borosilicate glasses containing MoO3

Borosilicate glass is an effective matrix for vitrification of high-level nuclear waste. However, the solubility of molybdenum is lower. In this paper, the impacts of Fe2O3 replacing SiO2 on the phase, glass structure, and chemical durability of a simplified calcium borosilicate glass containing molybdenum were investigated. According to XRD, Raman, and FTIR spectra, replacing SiO2 with Fe2O3 makes the glass structure polymerize first and then depolymerize. Furthermore, when Fe2O3 replaces SiO2 up to 5 mol%, the samples show a fully amorphous character, and the glasses show a more disordered structure. The solubility of Mo in the simplified calcium borosilicate glass can be enhanced by extending the depolymerization regions and introducing Fe3+ to compensate for the charge of [MoO4]2−. Moreover, the substitution of Fe2O3 can improve the chemical durability of glass waste form. As a result, the borosilicate glass containing 6 mol% Fe2O3 is a potential matrix to immobilize Mo-containing HLW.

Alkali field strength effects on optical, dielectric, and conducting properties of calcium borosilicate glasses

This paper reports the alkali field strength effect on structural, optical, dielectric, and conducting properties of calcium borosilicate glasses. Glass compositions 60SiO2–5B2O3–15CaO-20R2O (where R = Li, Na, K) are synthesized by melt-quench technique. The density shows an increasing trend with the increasing atomic weight of substituted alkali metal oxides. On the other hand, the hardness and elastic modulus are found to decrease from Li2O to K2O. The tendency of oxide ions to donate electrons is found to increase with decreasing field strength of alkali ions in the glass. The optical band gap of glasses is found in the insulating range, i.e. 4.27 eV–4.38 eV. The diffusion coefficient and conductivity of Li2O-containing glass is the highest followed by Na2O and K2O. Present synthesized glasses are found to be suitable for use as a substrate in thin film solar cells.

Alumina joints brazed by screen-printed B4C–SiO2 in air

In this study, B4C–SiO2 was employed as the joining material via a screen-printing method to join alumina (Al2O3) ceramics at 1000 °C in ambient air. Effects of mass ratios of B4C and SiO2 ranging from 1:0.5 to 1:2.5 on the composition, microstructure, and mechanical properties of the joints were investigated. When the content of SiO2 was equal or greater than that of B4C, the interlayer of the brazed joints was defect-free and consisted of Al4B2O9 whiskers and calcium borosilicate glass based on microscopically electronic analyses. With the content of SiO2 increased, the shear strength of the joints increased first and then decreased. The average shear strength of the joint reached the maximum value of 110 ± 19 MPa when the mass ratio of B4C to SiO2 was 1:2. The current study demonstrated that the screen-printed B4C–SiO2 system could be a very beneficial approach to obtain high strength Al2O3 joints with defect-free interlayer at relatively low joining temperatures in air.

Material characterization of WO3/Bi2O3 substituted calcium-borosilicate glasses: Structural, physical, mechanical properties and gamma-ray resistance competencies

This study aimed to discuss the experimental results of the elastic and structural properties in addition to the photon-shielding properties of a group of different WO3 content modified (60-x)Bi2O3–20B2O3–10SiO2–10CaO-xWO3 glasses. Glass samples with different concentrations of WO3 (0 ≤x ≤ 10 mol%) were labeled as BiW-00, BiW-2.5, BiW-05, BiW-7.5, and BiW-10. The samples were synthesised using the melt-quenching method. The measured glass density increased with increasing WO3 content. XRD patterns were gained to discover the amorphous network of the samples. The elastic parameters increased with increasing WO3 ratio. The mass attenuation coefficients (µm) were obtained experimentally at energies of 0.356, 0.662, 0.911, 1.173, and 1.332 MeV, respectively. The half value layer and mean free path values were determined using mass attenuation coefficeint values. The lowest half value layer and mean free path values were observed for the BiW-10 glass with the highest WO3 contribution (10% mol). It can be concluded that the addition of WO3 to the glass network progresses the elastic parameters and nuclear radiation protection qualities.

Characterization of immiscibility in calcium borosilicates used for the immobilization of Mo6+ under Au‐irradiation

AbstractThe aim of this paper was to assess factors affecting primary and secondary phase separation in simplified calcium borosilicate glasses studied for nuclear waste applications. Several glasses with varying [MoO3] and [B2O3] were synthesized and exposed to Au‐irradiation to examine compositional effects on glass structure and domain size of separated phases induced by accumulated radiation damage resulting from α‐decay over a ~1000 year timeframe. The produced glasses fell within the immiscibility dome of CaO−SiO2−B2O3 and showed a unique microstructure of embedded immiscibility with three identifiable amorphous phases according to electron microscopy, Raman spectroscopy, and diffraction. These glasses were then bombarded with 7 MeV Au3+ ions to a dose of 3 × 1014 ions/cm2 creating an estimated ~1 dpa of damage. Several changes to the morphology, spatial distribution, and size of secondary phases were observed, indicative of significant structural reorganization and changes to the chemical composition of each phase. A general mechanism of coalescence to form larger particles was observed for [MoO3] < 2.5 mol%, whereas segregation to form smaller more evenly distributed particles was seen for [B2O3] ≤ 15 mol% and [MoO3] ≥ 2.5 mol%. These microscopic changes were concurrent to surface‐bulk diffusion of Ca and/or Mo ions, where the direction of diffusion was dependent on [B2O3] with a barrier identified at ~20 mol%, as well as cross‐phase diffusion of said ions. These modifications occurred in part through the formation of distorted ring structures within the borosilicate network, which enabled the increased dissolution of isolated (MoO4)2− units. Au‐irradiation was therefore able to increase the solubility of molybdenum and alter the structure and composition of secondary phases with the extent of modification varying with [MoO3] and [B2O3]/[SiO2], though glasses notably remained heterogeneous. The collective results suggest that radiation and composition can both be used as design tools to modulate the domain size and distribution of separated phases in heterogeneous glasses.

The effect of particle size on radiation shielding properties for bismuth borosilicate glass

The aim of this work is to study the radiation shielding properties of size dependent bismuth in sodium calcium borosilicate glasses. The Bi2O3 in these glasses have the particle size in micrometer (M-BNCBS) have been compared the radiation shielding properties with the glasses that replaced the Bi2O3 with Bi nano-powder (N-BNCBS). The results show that the density of M-BNCBS and N-BNCBS is higher at higher concentration of Bi and the particle size of Bi does not affect to the density of glasses. The molar volumes increase with Bi content and show the higher in N-BNCBS with relative different increase with Bi content due to the NBOs more created. The N-BNCBS have the values of mass attenuation coefficients, effective atomic numbers and electron densities higher than M-BNCBS due to the larger electron cloud density in N-BNCBS. The half value layer of N-BNCBS found to be less than M-BNCBS. These results show that the particle size will affect the radiation shielding properties. Moreover, the radiation shielding properties of these glasses found to be better than Commercial window glass and some standard shielding concrete when compared.

Swift heavy ion-irradiated multi-phase calcium borosilicates: implications to molybdenum incorporation, microstructure, and network topology

A series of calcium borosilicate glasses with varying [B2O3], [MoO3], and [CaO] were prepared and subjected to 92 MeV Xe ions used to simulate the damage from long-term α-decay in nuclear waste glasses. Modifications to the solubility of molybdenum, the microstructure of separated phases, and the Si–O–B network topology were investigated following five irradiation experiments that achieved doses between 5 × 1012 and 1.8 × 1014 Xe ions/cm2 in order to test the hypotheses of whether irradiation would induce, propagate, or anneal phase separation. Using electron microscopy, EDS analysis, Raman spectroscopy, and XRD, irradiation was observed to increase the integration of MoO42− by increasing the structural disorder within and between heterogeneous amorphous phases. This occurred through Si/B-O-Si/B bond breakage and reformation of boroxyl and 3/4-membered SiO4 rings. De-mixing of the Si–O–B network concurrently enabled cross directional Ca and Mo diffusion along defect created pathways, which were prevalent along the interface between phases. The initiation and extent of these changes was dependent primarily on the [SiO2]/[B2O3] ratio, with [MoO3] having a secondary effect on influencing the defect population with increasing dose. Microstructurally, these changes to bonding caused a reduction in heterogeneities between amorphous phases by reducing the size and increasing the spatial distribution of immiscible droplets. This general increase in structural disorder prevented crystallization in most cases, but where precipitation was initiated by radiation, it was re-amorphized with increasing dose. These outcomes suggest that internal radiation can alter phase separation tie lines, and can therefore be used as a tool to design certain structural environments for long-term encapsulation of radioisotopes.

Tunable colors and applications of Dy3+/Eu3+ co‐doped CaO‐B2O3‐SiO2 glasses

AbstractA series of Dy3+/Eu3+ single‐ and co‐doped calcium borosilicate luminescent glasses were prepared by the conventional high temperature melt‐quenching method. A compact glass structure is obtained by the addition of Dy3+/Eu3+ ions, which is verified by the physical properties of synthetic glasses. As network modifiers, Dy3+/Eu3+ fill in the interspaces of glass network and contribute to the conversion of [BO3] to [BO4]. Dy3+/Eu3+ co‐doped calcium borosilicate glasses can emit white light, which consists of blue, yellow, and red light under 387 nm excitation. The emission spectra and decay curves of the white‐emitting glasses have proved the existence of energy transfer. The average lifetime of Dy3+ decreases from 0.251 to 0.165 ms with the increasing Eu3+ concentration. Changing rare earth ions concentration, CIE color coordinates of Dy3+/Eu3+ co‐doped glass shifts from cyan to white with increasing excitation wavelength. A white‐light emission is obtained when the concentration of Dy3+ and Eu3+ equals to 4% and 2%, respectively. Moreover, the Dy3+/Eu3+ co‐doped calcium borosilicate glass shows high‐thermal stability and it may be applicable for high‐quality white LEDs based on high power near ultraviolet (n‐UV) LED chip in the future.

An in-vitro bioactive, structural and degradation studies on B2O3–SiO2–P2O5–Na2O–CaO glass system incorporated with chromium ions

Calcium borosilicate glasses with composition 43B2O3–5SiO2–2 P2O5–20 Na2O–(30–x) CaO–x Cr2O3 with 0 ≤ x ≤ 1 mol%, have been prepared by the conventional melt-quenching technique. The samples were characterized by FTIR, UV-vis-absorption and X-ray diffraction techniques. The physico chemical properties such as density, molar volume, oxygen packing density and chromium ion concentration were also evaluated. The data obtained indicated that the Cr2O3 will break the bonds of the glass network by the creation of non bridging oxygens (NBO’s); as a result an increase in the volume of the glass network due to loosely packed structure. Results from FTIR, UV-vis.-spectroscopy studies indicated that Cr2O3 acted as a network modifier, by converting four coordinated to three coordinated boron atoms. In this context, we have examined the bioactivity of various concentrations of Cr2O3 doped glasses with the help of simulated body fluid (SBF). After immersion of glasses in the SBF, formation of hydroxyapatite layer on the surface was confirmed by XRD, FT-IR and SEM-EDS analysis. The solubility test data indicated that a clear increase of degradability of glass and significant change in the pH of the body fluid was observed with the addition of chromium. The results showed that partial substitution of Cr2O3 with CaO positively influenced the bioactivity. Thus bioactivity is increased with increase in the content of Cr2O3.

Construction and nonlinear optical characterization of CuO quantum dots doped Na2O–CaO–B2O3–SiO2 bulk glass

The spherical shape copper oxide (CuO) quantum dots (QDs) were successfully fabricated via copper basic calcium sodium borosilicate (Na2O–CaO–B2O3–SiO2) precursor obtained with a facile sol–gel technique. The microstructural analysis of doped QDs are systemically characterized, such as transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and X-ray photo-electron spectroscopy. And the results reveal that the CuO QDs with the small size are well dispersed doped in sodium calcium borosilicate glass. Remarkably, the CuO glass materials exhibit the good third-order optical nonlinear susceptibility χ(3) (1.379 × 10−12 esu), which was investigated by femto-second Z-scan technique at the wavelength of 1550 nm, pulse duration of 50 fs, repetition rate of 50 MHz. The glass hybrids displayed a reverse saturable absorption and self-focusing refraction performance. And the mechanism to explain the third-order nonlinearity of CuO glass may be predominantly originated from the surface plasmon resonance effect, the quantum confinement effect and partly from the thermal effect. Besides, it is interesting that the glass hybrids have significant nonlinear absorption effects that endow the material to the potential value of the application of optical limiting device.

Cytocompatibility studies of titania-doped calcium borosilicate bioactive glasses in-vitro

The present study aims to elucidate the applications of Titania (TiO2) doped calcium borosilicate glass as a biocompatible material in regenerative orthopedic applications. In this context, we have examined the bioactivity of various concentrations of TiO2 doped glasses with the help of simulated body fluid (SBF). Cytocompatibility, cell proliferation, and protein expression studies revealed the potential candidature of TiO2 doped glasses on osteoblast cell lines (MG-63). We hypothesized that TiO2 doped calcium borosilicate glasses are most cytocompatible material for bone implants. Glasses with composition 31B2O3-20SiO2-24.5Na2O-(24.5−x) CaO- x TiO2 (x=0,0.5,1,2) have been prepared by the conventional melt-quenching technique. After immersion of glasses in the SBF, formation of hydroxyapatite layer on the surface was confirmed by X-ray Diffractometer (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) and Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) analysis. Significant change in the pH of the body fluid was observed with the addition of titania. Degradation test was performed as per the ISO 10993. The results showed that partial substitution of TiO2 with CaO negatively influenced bioactivity; it decreased with increase in concentration of TiO2. Vickers hardness tester was used to measure the microhardness values of the prepared glasses. With the increasing of TiO2 content, the microhardness of the glass samples was increased from 545Hv to 576Hv. Cytocompatibility has been evaluated with MG-63 cells by using MTT assay. Further, we observed that there was no change in expressions of cyclin levels even after the incorporation of titania. The antibacterial properties were examined against E. coli and S. aureus. Strong antibacterial efficacy was observed for 2% TiO2 in the system. Hence it can be concluded that titania-doped borosilicate glasses may be used as potential materials in bone tissue engineering.

Structural investigation of calcium borosilicate glasses with varying Si/Ca ratios by infrared and Raman spectroscopy

Si/Ca ratio-dependent structure of borosilicate.

Dielectric properties of 0.95(Mg0.98Zn0.02)TiO3–0.05CaTiO3 ceramic sintered by calcium borosilicate glass ceramic doping

The effect of calcium borosilicate (CBS) glass ceramic on the phase formation, the microstructures and the microwave dielectric properties of 0.95(Mg0.98Zn0.02)TiO3–0.05CaTiO3 (MZCT) ceramics prepared via the conventional solid-state reaction route were investigated. It has been found that (Mg0.98Zn0.02)TiO3 and CaTiO3 are the main phases and a second phase (Mg0.98Zn0.02)Ti2O5 appeared in MZCT ceramics doped with CBS glass. As the content of CBS glass increased, the second phase (Mg0.98Zn0.02)Ti2O5 further enhanced. Appropriate CBS glass addition could effectively facilitate sintering of the ceramics, and well-densified microwave ceramics with uniform grains could be obtained under 1240 °C. An extremely high Q × f of 59,200 GHz together with an er of 21.42 and a τf value of −2.1 ppm/°C could be found for 0.95(Mg0.98Zn0.02)TiO3–0.05CaTiO3 specimen with 4 wt% CBS glass addition sintered at 1240 °C for 2 h. This study shows that appropriate addition of CBS glass could effectively decrease the sintering temperature of MZCT ceramics without deteriorating the ceramic performance.

The influence of local structure and surface morphology on the antibacterial activity of silver-containing calcium borosilicate glasses

A silver containing series of glasses starting from Ag-free 1.5B2O3·SiO·CaO parent glass and ending with 3mol% Ag2O was synthesized by the conventional melt quenching method and analyzed in order to correlate the composition and the structural peculiarities with the antibacterial effects. The structure and surface morphology of samples were characterized by X-ray diffraction (XRD), infrared (FTIR) and Raman spectroscopy, Scanning Electron Microscopy (SEM). X-ray photoelectron spectroscopy (XPS) was used to determine the nature of chemical bonding and the surface composition of the samples. The results indicate that all samples are vitreous and their local structure — mainly built by tetrahedral (BØ4‐), triangular (BØ3 and BØ2O−) borate species (Ø representing an oxygen atom bridging two boron atoms) and silicate Q1, Q2, Q3 units — is reactive to the silver oxide addition. Based on XPS data, both Ag+ and Ag0 ions are present on the surface of detected silver nanoparticles.Ag nanoparticles (AgNPs) embbeded in glasses were evaluated for their antimicrobial activity against the gram-positive and gram-negative bacteria, i.e. Staphylococcus aureus and Escherichia coli bacteria. The antibacterial effect of investigated samples increases simultaneously with the Ag2O content and AgNP dimension. The proposed mechanism is discussed in relation with the local structure, Ag+/Ag0 ratio and AgNP dimensions.

Effect of Eu2O3 concentration on luminescent properties of Ce/Tb/Eu co-doped calcium borosilicate glass for white LED

Luminescent properties of Ce/Tb/Eu co-doped calcium borosilicate glass were investigated through excitation and emission spectra, fluorescence lifetimes and colorimetric analysis. The spectra results show that the concentration quenching of Eu3+ ions occurs when the concentration of Eu2O3 ranges from 0.75mol% to 1.00mol% and Ce3+, Tb3+ and Eu2+ ions are all the donors which can transfer energy to Eu3+. It can be indicated from the analysis of lifetimes that through nonradiative transition, Tb3+ ions can accept energy from Eu2+ ions and also transfer energy to Eu3+ ions. Furthermore, the colorimetric analysis show that the correlated color temperatures (CCT) of Ce/Tb/Eu co-doped calcium borosilicate glass can be adjusted from cold white to warm white by controlling the concentration of Eu2O3.

Preparation and dielectric properties of BaTiO3-based X8R ceramics co-doped with BIT and CBS glass

The effects of Bi4Ti3O12 (BIT) on phase purity and dielectric properties of BaTiO3 (BT) ceramics have been investigated. Results show that BT samples doped with 1–3 mol% BIT adopt a single phase. However, secondary phase Bi2Ti2O7 is observed when BIT content exceeds 3 mol%. Tetragonality and the Curie temperature (TC) firstly increase and then decreases with an increase in BIT content. The 3 mol% BIT-doped BT ceramic sintered at 1,250 °C exhibits good dielectric properties of er = 2,692, tan δ = 0.0152, ρv = 5.8 × 1012 Ω cm, and the variation of dielectric constant as compared with that at room temperature is about −20 % at −55 °C and less than 11 % at 150 °C. It is found that the addition of calcium borosilicate glass (CBS) in BT-BIT ceramics can effectively lower the sintering temperature from 1,250 to 1,050 °C and further enhance the capacitance temperature stability. The permittivity decreases with an increase in CBS content from 1 to 10 wt%. Secondary phase BaBi4Ti4O15 exists in the CBS doped BT-3BIT systems. All of CBS doped samples satisfy the X8R specification. Typically, the sample with 3 wt% CBS has er = 1,789, tan δ = 0.0115, ρv = 9.67 × 1012 Ω cm. The variation of permittivity as compared with that at room temperature is about −12 % at −55 °C and less than ± 11 % at 150 °C. The as-prepared materials have great potential as EIA X8R-type multilayer ceramic capacitors.

Low temperature sintering and dielectric properties of Ba0.6Sr0.4TiO3–MgO composite ceramics with CaO–B2O3–SiO2 glass addition

Self-made glass frits (calcium borosilicate glasses) were employed as the sintering aids to reduce the sintering temperatures of Ba0.6Sr0.4TiO3 (for short BST)–MgO composite ceramics. The effects of CaO–B2O3–SiO2 (for short CBS) glass on the sintering behavior, microstructures and dielectric properties of BST–MgO ceramics have been investigated. The pure BST–MgO ceramics usually sintered at above 1350°C. It was found in our experiment that 20wt.% of CBS glass additives can reduce the sintering temperature to 850°C effectively. With increasing the content of CBS glasses, both of dielectric constant (ɛr) and dielectric loss (tanδ) were decreased. The samples sintered at 850°C for 2h with 20wt.% CBS glass addition consist of Ca4Ti3O10, Mg2SiO4, and BaCa2Mg (SiO4)2 phases, and possess good dielectric properties: moderate dielectric constant ɛr=66 and small dielectric loss tanδ=2.0×10−3.

Thermal and crystallization kinetics of yttrium and lanthanum calcium silicate glass sealants for solid oxide fuel cells

The crystallization kinetics of glass sealants is an essential parameter to check the suitability of glass as a sealant. The crystallization kinetic behavior of calcium borosilicate glasses were studied by Differential thermal analysis (DTA), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). These glasses were exposed for different heat treatment durations in oxidizing atmosphere at 800 and 900 °C. XRD results indicate the presence of La2SiO5 crystalline phase which increases the thermal expansion of the glasses. However, yttria doped calcium borosilicate glass (CaY) sample could not form any crystalline phase even after 10 h heat treatment at 900 °C. Moreover, the thermal expansion coefficient (TEC), viscosity values and fragility index of the glasses indicate that lanthanum doped calcium borosilicate glass (CaLa) might be a better glass sealant for solid oxide fuel cell as compared to CaY glass.

Sintering of titanate based dielectrics doped with lithium fluoride and calcium borosilicate glass

The effect of LiF and CBS glass additives on the microstructure and dielectric property of BaTiO3 (BT) ceramics was studied. The phase of BaLiF3 was observed from the interaction between BT and LiF when the samples were sintered at 900 °C for 1 h. Crystal grains with Ba and F in atomic ratios of 1:3 were observed from the SEM and TEM analysis of the microstructures. Abnormal grain growth (AGG) was observed to occur in the BT ceramics sintered at 950 °C. Further improvement to the composition was achieved by employing a two-stage process. This included CBS glass shell coating of the BT particles in the first stage, and the addition of LiF in the second stage. The composition thus formed had very good permittivity (1725) and an extremely low dielectric loss value (0.008).