Alkaline Earth Borate Glasses Research Articles

Physical, optical, thermal, structural and mechanical properties of alkaline earth borate glasses

Binary alkaline earth borate glasses were synthesized via the melt quenching technique. The density and molar volume of the resultant glasses were determined experimentally. The glass optical basicity has been found to increase with the glass polarizability. The optical properties of the glasses were comprehensively analyzed, revealing a shift in the cutoff wavelength towards longer wavelengths with increasing glass optical basicity. Additionally, the optical band gap (Eg) was estimated. Structural investigations unveiled an increase in the abundance of BO4 units as the glass optical basicity increased. Furthermore, the glass transition temperature was observed to decrease with decreasing cation field strength. Glass packing density and B2O3 packing factor were calculated to assess structural variations. The longitudinal and shear velocities were determined using the pulse echo technique, providing insights into the elastic moduli of the glasses. The Makishima and Mackenzie approach was employed to predict the elastic moduli, yielding results in good agreement with experimental data. This comprehensive analysis sheds light on the relationship between composition, structure, and mechanical properties of binary alkaline earth borate glasses, offering valuable insights for potential applications.

Continuous trap distribution and variation of optical properties with concentration in oxi-fluoroborate glass doped with Nd3+

Alkaline earth borate glasses are being studied due to their interesting structure and properties. Here, the optical properties of some barium oxyfluoride glasses are reported. The absorption spectra by means of Judd Ofelt theory, the room temperature luminescence, and the thermoluminescence (TL) response as a function of dopant concentration were studied. The effect of the concentration on the thermal stability and the glass structure was also analyzed. The incorporation of Nd 3+ affects not only the optical properties but also the thermal ones. From Raman spectroscopy, no great differences were observed among undoped and doped glass samples. Judd-Ofelt parameters are lower or comparable to other borate and silicate systems. The temperature of the maximum intensity on the TL curve does not change with the irradiation dose, indicating samples follow a first-order kinetic model. However, the detailed TL analyses evidenced a continuous distribution of the activation energy and the signal stability after irradiation was also studied and interpreted in the same way. The results presented here indicate that the oxy-fluoride borate glasses are promising materials for TL applications.

Optical properties of alkaline earth borate glasses

Borate glasses containing fixed concentrations of heavy metal oxides (MO= ZnO, PbO, TeO2, Bi2O3) and alkaline earth oxides (R= Mg, Ca, Sr, Ba) are prepared by melt quenching technique. The optical band gap values are estimated from the optical absorption spectra using absorption spectrum fitting (ASF) method. The values of electronic polarizability, optical basicity and interaction parameters of the glass were discussed. The increment of refractive index values in each series is attributed to the substitution of alkaline earth oxides of increasing mass. Optical band gap (Eopt) values decreased with the replacement of RO oxides in the glass matrix. The cut-off wavelengths have shown a red shift with composition. The decrease in optical band gap values and consequently increase in Urbach’s energies confirms more extension of the localized states within the band gap. As a result there shall be an increase in the disorder of the glass network. The variation in optical parameters is owing to substitution of RO oxides in MO-B2O3 glass network.Keywords: alkaline earth borate glasses, optical band gap, Urbach energy, refractive index, electronic polarizability, molar refraction

Correlation between emission properties, valence states of Ce and chemical compositions of alkaline earth borate glasses

Although there are many reports investigating emission properties of Ce3+ centers, there is little report on the quantitative Ce3+/(Ce3++Ce4+) ratio, which is one of the most fundamental factors for designing phosphors. In this report, we have investigated the correlation among the optical and emission properties of Ce-doped alkaline earth borate glasses with the Ce3+/(Ce3++Ce4+) ratio determined by X-ray absorption near-edge structure analyses. It is confirmed that the additional carbon increases the population of Ce3+, which is also suggested from the optical absorption edge, Eg opt, due to Ce and the quantum yield (QY). We have revealed that the Ce3+ concentration of the Sr-substituted glass is completely the same as that of the Ca-substituted one that exhibits the highest efficiency, even though the Ce3+ ratio is suggested to depend on the substitution spices from the Eg opt and QY. Therefore, we can conclude that not only the Ce3+ amount but also the local structures of Ce3+ affect the emission properties. In other words, the luminescent efficiency of the Ce3+ centers in amorphous materials strongly depends on the various local coordination states.

Emission properties of Ce-doped alkaline earth borate glasses for scintillator applications

We investigate the photoluminescence (PL) and X-ray-induced luminescence properties of 0.1 mol% Ce-doped MO-B2O3 (M = Ca, Sr, and Ba) glasses. We also determine the Ce3+/(Ce3++Ce4+) ratio by X-ray absorption near-edge structure analyses. The emission intensities of PL, X-ray scintillation, and thermally stimulated luminescence (TSL) depend on the host glass composition. The order of the PL intensity from highest to lowest is as follows: Ca-substituted glass, Ba-substituted glass, and Sr-substituted glass. Our results suggest that the optical absorption edge and quantum yield (QY) are influenced by the local coordination state of Ce3+, which, in turn, is likely to be affected by the optical basicity. The order of the X-ray scintillation intensity from highest to lowest is reverse of that of the PL intensity. This is probably because the interaction probability of X-rays with matter depends on the effective atomic number of the material and the effective atomic number has a stronger influence on the scintillation intensity than does the QY. Though the TSL glow curves reveal that the density and energy depth of the trap sites depend on the substituted alkaline earth oxides, we are unable to correlate the electron spin resonance (ESR) spectra with the TSL results. Therefore, it is considered that the ESR active sites are not responsible for the TSL in these systems.

Dy^3+ doped borate glasses for laser illumination

Intense multi-peak warm yellowish-white fluorescence emissions of Dy3+ are exhibited in alkaline-earth borate glasses under the excitation of a blue laser. The net emission power and net emission photon number are identified to be 498.23μW and 14.28 × 1014cps, respectively, and the quantum yield is as high as 23.10% in 2.0wt% Dy2O3 doped alkaline-earth borate glass under the excitation of a 453nm blue laser with 14.13mW power. Anticipation of fluorescence color reveals that white luminescence can be achieved when the intensity ratio between residual laser light and Dy3+ emission reaches the appropriate range. By the introduction of Ce3+, the excitation wavelength range and the emission intensity of Dy3+ in alkaline-earth borate glasses are expanded to UVB region and improved by a maximum sensitization factor of 38.2, respectively, demonstrating the utilizability of a UV pumping laser for Ce3+−Dy3+ codoped alkaline-earth borate glasses. Efficient fluorescence emission and realizable white lighting in Dy3+ doped alkaline-earth borate glasses under the laser excitation will promote the development of laser illumination devices.

Statistical approach to study of lithium magnesium metaborate glasses

AbstractAlkali borate glasses and alkaline earth borate glasses are commonly used materials in the field of optoelectronics. Infrared (FTIR) and Raman spectroscopy are valuable tools for structural investigation of borate glass networks. The compositional and structural variety of lithium magnesium metaborate glasses is usually determined by traditional instrumental methods. In this study a data set is classified by structural and physicochemical parameters (FTIR, Raman spectra, glass transition temperature-Tg). Characterisation of magnesium containing metaborate glasses by multivariate statistics (hierarchical cluster analysis) to reveal potential relationships (similarity or dissimilarity) between the type of glasses included in the data set using specific structural features available in the literature is conducted. The clustering of the glass objects indicates a good separation of different magnesium containing borate glass compositions. The grouping of variables concerning Tg and structural data for BO3 and BO4 linkage confirms that BO4/BO3 ratios strongly affect Tg. Additionally, patterns of similarity could be detected not only between the glass composition but also between the features (variables) describing the glasses. The proposed approach can be further used as an expert tool for glass properties prediction or fingerprinting (identification of unknown compositions).

Sm3+-doped alkaline earth borate glasses as UV→visible photon conversion layer for solar cells

Intense multi-peak red fluorescence emissions of Sm3+ are exhibited in alkaline-earth borate (LKZBSB) glasses under UV radiation. The spontaneous emission probabilities Arad corresponding to the 4G5/2→6HJ (J=5/2, 7/2, 9/2 and 11/2) transitions are derived to be 24.74, 129.72, 117.03 and 32.23s−1, respectively, and the relevant stimulated emission cross-sections σem are 0.77×10−22, 4.46×10−22, 5.05×10−22 and 1.38×10−22cm2, confirming the effectiveness of red luminescence in Sm3+-doped LKZBSB glasses. Quantitative characterization through the evaluation of absolute spectral parameters reveals that the quantum yield of Sm3+-doped LKZBSB glasses is as high as 13.29%. Furthermore, with the introduction of Ce3+, the effective excitation wavelength range and the emission intensity of Sm3+ in LKZBSB glasses are remarkably expanded and improved by a maximum sensitization factor of 9.02 in the UVB region. These results demonstrate that the present glass system has promising potential as an efficient UV→visible photon conversion layer for the enhancement of solar cell efficiency, including appealing applications in outer space.

High-efficiency fluorescence radiation of Dy3+ in alkaline earth borate glasses

Dy3+-doped alkaline-earth borate glasses (LKZBSB) with high quantum yield and multifarious emission channels have been fabricated and efficient warm yellowish-white fluorescence is presented under UV light excitation. Judd–Ofelt parameters Ω2=5.36×10−20cm2, Ω4=1.46×10−20cm2 and Ω6=1.95×10−20cm2 indicate a high asymmetrical and covalent environment in the optical glasses. The maximum stimulated emission cross-sections σem-max corresponding to the 4F9/2→6H15/2, 4F9/2→6H13/2, 4F9/2→6H11/2 and 4F9/2→(6H9/2, 6F11/2) transitions are derived to be 2.64×10−22, 20.07×10−22, 3.45×10−22 and 9.31×10−22cm2, respectively, and the relevant spontaneous emission probabilities Arad are 174.08, 616.07, 68.95 and 87.10s−1. Quantitative characterization reveals that Dy3+-doped LKZBSB glasses exhibit a quantum yield as high as 16.65%, confirming that the effectiveness of the warm yellowish-white luminescence in Dy3+-doped LKZBSB glasses. Multifarious emission channels and high quantum yield illustrate the great advantages of Dy3+-doped LKZBSB glasses in developing fiber-lighting sources, display devices, tunable visible lasers, and optical signal amplifiers.

Study the influence of zinc oxide addition on cobalt doped alkaline earth borate glasses

The glasses of the composition 79.9B2O3–20BaO–0.1Co3O4 doped with different concentrations of ZnO (5, 10, 15, 20, 25 and 30mol%) were prepared using melt quenching technique. Various studies such as XRD, density, theoretical optical basicity, FT-IR and optical absorption have been carried out to study the role of ZnO on the physical and structural properties of the investigated system. Powder X-ray diffraction patterns confirmed the glassy nature of all the glassy samples. The density and molar volume of glassy samples showed opposite behavior to each other. An increment of the theoretical optical basicity with increasing ZnO content, which is due to an increase in the polarizability and a decrease in the single bond strength is observed. FT-IR analysis revealed that an increase in non-bridging oxygen’s (NBO’s) up to ZnO⩽15mol% and then a decrease at ZnO>15mol%. The results indicated that the Zn2+ ions are likely to occupy network modifier positions at a concentration of ZnO⩽15mol%. Above which these ions occupy network forming positions. From ultraviolet absorption edges calculations, the optical band gap energy and steepness parameter decrease whilst Urbach energy and refractive index increase by the addition of ZnO up to 15mol% above which then the behavior follows reversal trend. The values of the crystal field strength and the interelectronic repulsion Racah parameter calculated from the optical transitions energies of cobalt doped glassy samples. All prepared samples exhibit blue color, indicating that mostly Co ions are acted upon by tetrahedral ligand field.

Thermal properties of alkaline and alkaline-earth borate glasses

Thermal properties of alkaline and alkaline-earth borate glasses

Effect of SiO2 and Al2O3 addition on the density, Tg and CTE of mixed alkali – alkaline earth borate glass

Mixed alkali — alkaline earth borate glasses, with the addition of silica and alumina, have been studied for their density, Tg and CTE with a view of exploring the applicability of these glasses in glass to metal sealing applications. It has been observed that silica addition results in an increase in density and Tg while the alumina addition decreases the density and Tg. The variation in CTE exhibits minima with the addition of both, silica and alumina. An attempt is made here to explain the observed variations in the properties on the basis of different mass of the additives, number of non bridging oxygens (NBOs) and other changes in the glass network.

Short-range structure of alkaline-earth borate glasses by pulsed neutron diffraction and molecular dynamics simulation

The structure of vitreous MO· nB 2O 3 (M=Ca and Ba; n=2, 3 and 4) has been studied by pulsed neutron diffraction measurement with the help of molecular dynamics (MD) simulation. The first and second peaks assigned to the nearest-neighbor B–O and O–O correlations, respectively, in the obtained total pair distribution functions shifted little with increasing MO content, while the asymmetry of the first peak increased significantly with MO content; these results are different from those for potassium borate glasses. It was inferred that the BO 3 and BO 4 units are better defined in these alkaline-earth borate glasses than those in the potassium borate glasses. Both the full-width at half maximum (FWHM) of the first peak and the average co-ordination number of O around B clearly increased as MO content increased which is the same behavior with alkali borate glasses. The fraction of four-co-ordinated B showed a larger deviation from x/(1− x) for CaO–B 2O 3 glasses than that for BaO–B 2O 3 glasses which shows a different dependence of the deviation on cation size from that in alkali borate glasses, and is in good agreement with the results from MD simulation.

XAFS Studies of Alkaline-Earth Borate Glasses

The local structure obtained from calcium K-edge XAFS experiments in CaO-B2O3 glasses is described. The average coordination number of oxygen around Ca2+ ions and the mean distance for Ca-O are found to be approximately 6 and 2.40∼2.41Å, respectively. The Ca2+ ions have a disordered octahedral geometry and a strong preference to reside in vicinity of negatively charged non-bridging and bridging oxygen in the large cages of the B-O network structure. The XAFS results are in good agreement with MD simulation results.

Application of Free Volume Theory to Transport Phenomena in Molten Alkali and Alkaline Earth Borate Glasses

Application of Free Volume Theory to Transport Phenomena in Molten Alkali and Alkaline Earth Borate Glasses

The structure of borate glasses studied by Raman scattering

Raman spectra of alkali and alkaline-earth borate glasses are reported. These spectra are used to discuss the molecular structure of the glasses. The influence of additions of Al 2O 3 on the structure of alkali borate glasses is also presented. The experimental evidence indicates that the same type of groups are present in borate glasses as in crystalline borates. The presence of tetraborate, metaborate, pyroborate and orthoborate groups in borate glasses is strongly suggested by the Raman spectra.

Optical Spectra of Chromium in Borate and Silicate Glasses

Optical absorption spectra have been obtained on Cr3+ in alkali borate, alkali silicate and alkaline earth borate glasses. The assignments for bands ν1∼ν5 were made on the basis of octahedrally coordinated Cr3+ in the glasses and their band positions were determined. The values of three parameters, namely the crystal field strength, Dq, the Racah B and Racah C parameters, were calculated.The results indicate that;(1) Dq value of alkali borate glasses increases with increasing concentration of alkali oxide up to about 15mole% but it changes anomalously in the composition range of 15∼20mole%.(2) Dq value of alkaline earth borate glasses increases with increasing concentration of alkaline earth oxide.(3) On the contrary, in alkali silicate glasses the value decreases with increasing alkali oxide content.(4) As for the effect of kind of ion an increase of Dq value of the glass is in the order Li2O>Na2O>K2O and CaO>SrO>BaO for the same molar concentration of the oxide

Optical and ESR Spectra of Nickel-Containing Alkaline Earth Borate Glasses

The optical and paramagnetic resonance spectra have been obtained for divalent nickel ions in BaO⋅(5.1-1.5)B2O3, SrO⋅(3-1.5)B2O3 and CaO⋅(3-1.5)B2O3 glasses. The coordination about the nickel ion sites is found to be octahedral in all the glasses. Absorption bands due to tetrahedrally coordinated nickel ions are not observed. The crystal field splitting parameter 10 Dq decreases with the amount of alkaline earth contents in these three series of glasses, and also decreases in the sequence of CaO, SrO and BaO containing glasses if these alkaline earth contents are the same in each series of glasses. The value of the Racah parameter B and the spin-orbit coupling coefficient are both less than those values for free nickel ion. This fact is accounted for by introducing weak covalent Ni-O bonds. The covalency is found to become predominant in the order of BaO, SrO and CaO containing glasses.

Viscosity, Density, and Electrical Resistivity of Molten Alkaline‐Earth Borate Glasses with 3 Mole % of Potassium Oxide

Viscosity, density, and electrical resistivity were determined on three series of molten alkaline‐earth borate glasses, each containing 3 mole % of potassium oxide. A previous investigation of these properties of the binary alkaline‐earth borates was limited by the formation of two immiscible liquids at low alkaline‐earth oxide concentrations. To overcome this difficulty 3 mole % of K2O was added to each composition. The properties of this new series of glasses were compared with the previous work. The densities at room and elevated temperatures were in the order BaO > SrO > CaO on a mole per cent basis. The reverse order was noted for the viscosity data. The electrical resistivity decreased with increasing concentration of alkaline‐earth oxide at 1000°C. and at 1100°C. but increased at 800°C. and at 900°C.

Compressibility of Binary Alkaline‐Earth Borate Glasses at High Pressures

Compression data to 10,000 atm. were obtained for a series of barium, strontium, and calcium borate glasses at 21°C. The compressibility was found to be in the order Ba > Sr > Ca at corresponding molar concentrations and was not appreciably affected by pressure in the experimental pressure range. Comparison of data on alkali and alkaline‐earth borate glasses shows that the compressibility at corresponding molar concentrations is smaller in the alkaline‐earth glasses. Numerical comparisons at appropriate compositions show that a large part of the decreased compressibility produced by the alkaline‐earth oxides arises from electrovalent sources.