Full color and tunable white emitting in ternary Ce/Tb/Sm Co-doped CaO–B2O3–SiO2 glasses

A series of luminescent glasses composed of CaO–B₂O₃–SiO₂ co-doped with cerium oxide (CeO₂), terbium oxide (Tb₄O₇) and samarium oxide (Sm₂O₃) were prepared by high temperature melting method, aiming to realize the white emitting and tunable luminescent color in the glass matrix. The full colors including blue, green and reddish orange emitting were observed simultaneously in the photoluminescent spectra of ternary Ce/Tb/Sm co-doped CaO–B₂O₃–SiO₂ glasses excited by ultraviolet light. It is shown that the combination of these three emitting allows the realization of white light emitting in ternary co-doped CaO–B₂O₃–SiO₂ glasses. Furthermore, the tunable luminescent color and chromaticity parameters could be realized by varying the content of dopant in the glass matrix, which makes these co-doped glasses good candidates for white light emitting diodes (LEDs).     

Optical absorption of cobalt (II) in binary thallium borate glasses

The optical absorption spectra of cobalt (II) in Tl₂OB₂O₃ glasses have been studied and compared with those in binary alkali borate glasses. In thallium borate glasses cobalt (II) may be present in octahedral and/or in tetrahedral symmetry depending upon the composition of the glass. In low thallium borate glasses cobalt (II) is octahedral while the concentration of tetrahedral cobalt (II) increases with increasing Tl₂O content of the glass; the formation of tetrahedral cobalt (II) becomes noticeable when the concentration of Tl₂O reaches above the critical concentration of about 19 mol %. The ligand field parameters: 10Dq and B have been calculated from the absorption spectra of cobalt (II) in different glasses and it has been found that the Racah parameter, B, is more in Tl₂OB₂O₃ glasses than those in Na₂OB₂O₃ or K₂OB₂O₃ glasses of corresponding molar composition. This indicates that the donor capacity of the BO₄ group in thallium borate glasses is lower than that in alkali borate glasses; this is consistent with the NMR results in Tl₂OB₂O₃ glasses containing less than 20 mol % Tl₂O where three BO₄ groups have been found to form with each Tl₂O unit added.     

Raman spectroscopic investigation of the structure of silicate glasses (II). Soda-alkaline earth-alumina ternary and quaternary glasses

Raman spectra of some ternary and quaternary glasses in the system Na₂OCaOMgOAl₂O₃SiO₂ are presented. The spectra are interpreted in terms of the structural alteration of the glass as the composition is altered from the binary end members to more complicated glasses. Addition of CaO and MgO to soda-silica glasses act only to increase the disorder of the network slightly. Addition of Al₂O₃ greatly modifies the network. In some soda-lime-aluminosiliscate compositions an estimate can be made of the amount of aluminum in four- and six-fold coordination. It is shown that the amounts of four- and sixfold coordinated aluminum depend on the glass composition.     

Pressure effects on electrical conduction in glasses

Electrical conduction in various inorganic glasses was studied as a function of hydrostatic pressure up to 2000 atm and phenomenologically classified into electronic, ionic and mixed types. In electronically conducting glasses such as AsSe chalcogenide glasses and Fe₂O₃P₂O₅ glass, the conduction is enhanced by application of pressure. On the other hand in ionically conducting glass such as Na₂OB₂O₃ glass, the conduction is suppressed through the concept of an activation volume. The compatibility of electronic and ionic conduction processes in glasses such as Ag-doped AsSe glasses and Bi₂O₃B₂O₃ glass, which have more complex conduction processes, was discussed from these aspects.     

Raman spectroscopy of calcium aluminate glasses and crystals

Solar furnace melting and fast-quench techniques have been used to prepare calcium aluminate glasses from 75 mol% CaO to 82 mol% Al₂O₃, which have been studied by Raman spectroscopy. The CaAl₂O₄ glass spectrum may be interpreted in terms of a fully-polymerized network of tetrahedral aluminate units, which is depolymerized on addition of CaO component analogous to binary silicate systems. The spectra of glasses with higher alumina content than CaAl₂O₄ may not be simply interpreted and a structural model is proposed which would be consistent with the glass spectra and with observed crystal structures along the CaAl₂O₄Al₂O₃ join. This model suggests formation of highly condensed aluminate tetrahedral on initial addition of alumina, with the appearance of aluminate polyhedra of higher average coordination at higher alumina content. Similar high coordination polyhedral are also suggested for a limited composition range along the CaOCaAl₂O₄ join. These interpretations are compared with the results of a previous study in the SiO₂Al₂O₃ glass system.     

Anomalous physical properties and Raman spectra of glassy B2O3BaTiO3Na2O materials

Anomalous physical properties (refractive index and density) of B₂O₃BaTiO₃Na₂O ternay glasses are determined and discussed on the basis of the structure present in the glasses and evidenced by vibrational Raman spectroscopy.These glasses behave in a manner analogous to the alkali B₂O₃X₂O binary glasses for molar ratio R = basic oxide/B₂O₃ up to 0.3, with oxygen binding by means of bridging bonds while boron coordination changes from the trigonal to tetrahedral type. The phenomenon is indicated by a progressive weakening of the 806 cm^?1 peak (attributable to a breathing vibration of the boroxol unit) and by a concomitant strengthening of the ～775 cm^?1 peak (attributable to a vibrational mode of boroxol units, or derived units, containing at least one 4-coordinate boron atom). For higher R values the Raman spectra bring to light the progressive demolition of the structural units responsible for the 775 cm^?1 Raman peak, which gives rise (the transformation is complete for R ～ 1) to two new main structural units, orthoborate [BTi₄O₁₀]^?1 (peak at 845 cm^?1) and metaborate BO₂^? (peak at 715 cm^?1).     

Scattering losses in binary borate glasses

The purpose of this paper is to examine the potential of three binary borate glasses; namely PbOB₂O₃, K₂OB₂O₃ and Li₂OB₂O₃ as candidates for fabrication of low optical loss and low cost fiber-glass wave-guides.The importance of ultrasonic measurements as the first step in a systematic search for a glass with low optical loss, is discussed. Results of ultrasonic measurements of PbOB₂O₃ system are then presented. Using these results and the published results for the K₂OB₂O₃ and Li₂OB₂O₃ systems, estimates of the magnitude of density fluctuations as a function of composition have been made for each system. Comparison with the previously published results on the K₂OSiO₂ system suggests that out of the three systems chosen, only 50 mole % Li₂O50 mole % B₂O₃ glass is a likely candidate for the production of low optical loss glass fibers.     

Glasses and glass-ceramics from naturally occurring CaOMgOAl2O3SiO2 materials (I) glass formation and properties

Once oil is extracted from oil shales, the inorganic solid which remains is from the CaOMgOAl₂O₃SiO₂ system. The material is easily melted and forms a glass upon cooling. Its viscosity in the forming region is actually less than that of commercial soda-lime glass. Shale glasses exhibit excellent dielectric behavior, while their other properties are generally comparable to commercial glasses. These glasses appear to be promising materials for future applications.     

Nuclear magnetic resonance studies of the glasses in the system Na2OB2O3SiO2

The ¹¹B NMR spectra have been used to study the structure of glasses in the system Na₂OB₂O₃SiO₂. The fraction of BO₄ units, and the fraction of BO₃ units with one or two nonbridging oxygens, are measured and analyzed according to a structural model. The results indicate that: (1) for a sodium oxide to boron oxide ratio of 0.5 or less, the Na⁺¹ ions are attracted primarily by the borate network; therefore, the ternary glasses can be viewed as binary sodium borate glasses diluted by SiO₂; (2) when the sodium oxide to boron oxide ratio exceeds 0.5, the additional Na₂O results in the formation of [BSi₄O₁₀]^?1 units at the expense of diborate and SiO₄ units. In this process, Na⁺¹ ions are still taken up only by the borate network. After all the available SiO₄ units are consumed to form [BSi₄O₁₀]^?1 units, additional Na⁺¹ ions are proportionally shared between the borate and silicate networks.     

Fracture toughness-composition relationship in some binary and ternary glass systems

Measurements of the critical stress intensity factor K_Ic are reported for glasses in the Na₂OSiO₂, PbOSiO₂, ZnOB₂O₃, PbOB₂O₃, Na₂OGeO₂ and 20Na₂O?(80 ? x) B₂O₃ ? xSiO₂ systems. The variations of K_Ic with composition are not directly related to the simultaneous variations of Young's modulus. A tentative interpretation is given.     

Electronic structure and properties of oxide glasses (II) Basicity measured by copper(II) ion probe in Na2OP2O5, K2OB2O3 and K2SO4ZnSO4 glasses

The correlation between the basicity of oxygens measured by the Cu(II) ion probe and the non-bonding electron density on oxygens in alkali borate glasses was considered. The basicity was measured for K₂OB₂O₃, Na₂OP₂O₅ and K₂SO₄ZnSO₄ glasses and categorized into two types, δ and π, according to the symmetry property of the bonding between a Cu(II) ion and oxygen. The π basicity for borate and phosphate glasses showed an abrupt increase in the vicinity of 17 and 50 mol% alkali oxide, respectively. The values of π-type basicity varied with the composition of glass, being larger in the order: sulfate < phosphate ? borate, whereas δ basicity was constant irrespective of the glass composition. Such a change of the basicity with the composition of glass was interpreted in terms of behavior of non-bonding levels of the ligand oxygens in a glass network.     

X-ray diffraction studies of glasses in the systems Na2OMeOSiO2 (MeMg,Zn, Ca,Ba)

X-ray diffraction studies of glasses in the following ternary systems have been made: Na₂OMgOSiO₂, Na₂OZnOSiO₂, Na₂OCaOSiO₂ and Na₂OBaOSiO₂. The following heavy atom substitutions have been used: Ag for Na and Ge for Si. The changes in the electron radial distribution curves resulting from AgNa replacement can be explained as amplifications of relatively well-defined NaSi distances, which are nearly the same in all the glasses investigated. The GeSi substitution causes changes which can be explained on the basis of isostructural GeSi substitutions.     

Glass formation and structure of Na2SSiO2 and Na2SB2O3 glasses

Glass-forming regions of the systems Na₂SSiO₂ and Na₂SB₂O₃ have been investigated in order to clarify whether Na₂S could be substituted for Na₂O in sodium silicate or borate glasses, and the results were interpreted in terms of the structures of silicate and borate glasses. No difference was found in the glass-forming range of SiO₂ content between the Na₂SSiO₂ and Na₂OSiO₂ systems, and the red color of Na₂SSiO₂ glasses suggests that the formation of polysulfides in the glass structure is probably due to the entrance of sulfur ions in the non-bridging sites of the glass network. On the other hand, not all of the sulfur added to the glass batches could be retained in the Na₂SB₂O₃ glasses and the amount remaining in the glass products changed depending upon the amount of sodium ions in the glasses. Only a trace of sulfur was observed in the glasses containing less than 13 mol% of Na₂S in the batches, but the sulfur content in the glasses increased steeply with sodium content up to 35 mol%, reached the maximum and then decreased slowly with sodium content. The insolubility of sulfur in the glasses with low sodium content was interpreted based on the compositional dependence of basicity of alkali-borate glasses, and the change in solubility of sulfur with sodium concentration was explained based on the well-known boron anomaly caused by the change in the coordination state of boron and on the formation of non-bridging oxygens or sulfurs in the glass structure.     

Ultrasound propagation in glasses in the metastable immiscibility region of the sodium borosilicate system

Measurements of ultrasound wave velocity and attenuation have been made between 1.3 K and 400 K in a series of both quenched and heat-treated Na₂OB₂O₃SiO₂ glasses. As in many other inorganic glasses, the ultrasound attenuation of both longitudinal and shear waves below room temperature is dominated by a broad and intense loss peak; the height and temperature of the peak maximum are frequency sensitive. The loss peak characteristics are consistent with a structural relaxation mechanism with a distribution of activation energies and this model is used to analyse the data. The features of the acoustic loss peak and also the absolute value and temperature coefficient of ultrasound velocity are strongly dependent on the total Na₂O network modifier content of the glasses. The ultrasound wave propagation is also affected by phase-separation inducing heat treatment: a steady rise in the height of the acoustic loss peak and an upward shift in the peak temperature takes place with increasing time of heat treatment at 550°C, a finding which suggests that structural rearrangements are still occurring in the individual glassy phases even after long periods of heat treatment. It is proposed that heat treatment causes migration of Na⁺ ions away from BOB bonds in the B₂O₃ rich phase.     

Effect of fictive temperature on the optical absorption of cobalt (II) and nickel (II) in some phosphate glasses

The optical absorption of cobalt (II) in Na₂O, 4P₂O₅ melts and in H₂ONaCl mixtures has been studied at different temperatures; the equilibrium: octahedral ? tetrahedral shifted towards the right with increasing temperature in both solvents. The optical absorption of cobalt (II) and nickel (II) has been studied in a series of metaphosphate glasses: Na₂OCaOP₂O₅, and it has been shown that the equilibrium octahedral/tetrahedral ratio of these ions measured at room temperature can be correlated with the transformation temperature of these glasses. The colour of cobalt (II) or nickel (II) containing CaO·P₂O₅ glasses has been found to be significantly dependent on thermal history; the intensity of optical absorption changed reversibly on heat treatment at the transformation range of the glass.     

NMR studies on rapidly solidified SiO2Al2O3 and SiO2Al2O3Na2O-glasses

²⁷Al and ²⁹Si MAS NMR studies were performed on roller-quenched SiO₂Al₂O₃-glasses with Al₂O₃ contents ranging from 10 to 60 mol% and on SiO₂Al₂O₃Na₂O glasses containing 10 mol% Al₂O₃ and 2.5 to 10 mol% Na₂O. Pure aluminium silicate glasses show NMR peaks at 0, 30 and 60 ppm. The frequency distribution of the different Al-sites is not affected by the glass composition. In glasses of the system SiO₂Al₂O₃Na₂O the 30 ppm peak decreases to zero as the Na₂O content increases. The 30 ppm peak is assigned to distorted triclustered AlO-tetrahedra, rather than to fivefold coordinated Al. Triclustering of tetrahedra may provide for charge neutrality in glasses with molar excess of Al₂O₃ over Na₂O. As charge balance is increasingly achieved by addition of alkali ions, the tendency of tetrahedral triclustering is reduced, reflected by the disappearance of the 30 ppm peak in glasses containing ≥ 7.5 mol% Na₂O.     

Crystallization of gels and glasses made from hot-pressed gels

Silica gels were prepared by two different methods: (1) destabilization of a silica hydrosol (gel 1); (2) hydrolysis and polycondensation of a tetra-methoxysilane (gel 2). The crystallization of the gels was then studied as a function of the temperature by means of X-ray diffraction. It was evident that the crystallization was strongly influenced by the amount of alkali oxides present in the gel. It is effectively the concentration of akali impurities which could explain the lower temperature of crystallization necessary for gel 1 compared with that of gel 2. During the crystallization of the gel containing Na₂O the crystalline phase of silica which appears first is the cristobalite; with Li₂O it is quartz. The effect of additives such as boric anhydride was studied. This oxide was found to reduce the tendency of the gels to crystallize. The glasses of the system SiO₂B₂O₃ obtained by the hot-pressing of the gels confirmed this phenomenon. Above 10 mol% B₂O₃ it was impossible to crystallize the gels and the glasses of this system under two hours.     

Glass formation in the systems (K or Cs)2O(Nb or Ta)2O5Al2O3

The glass-forming ability of melts in the systems K₂O(Nb and/or Ta)₂O₅Al₂O₃ as well as those in which K₂O was replaced with Li₂O, Na₂O, Cs₂O, BaO or PbO was investigated. Some melts in the systems (K or Cs)₂O(Nb and/or Ta)₂O₅Al₂O₃ could be made into glasses by cooling, yielding practically useful amounts. The structures of these glasses were discussed on the basis of their infrared spectroscopic and X-ray emission spectroscopic analyses.     

Some features of EPR and optical spectra of vanadium in aluminophosphate glasses

The EPR and optical spectra of vanadium in glasses of ternary Al₂O₃P₂O₅SiO₂ and Al₂O₃P₂O₅B₂O₃ systems have been measured. The results were compared with earlier data for vanadium in binary phosphate, aluminophosphate and silicaphosphate glasses and with results of de-Biasi for V⁴⁺ in crystalline powder α-crystobalite AlPO₄. The superpositions of two hyperfine spectra (ASB-I and ASB-II) were found for many glasses of ternary systems. Both spectra can be attributed to VO²⁺ ions. The intensity ratio of the ASB-II spectrum to ASB-I depends on glass composition but is great (> 7) for all the glasses. Only the ASB-II spectrum was observed in glasses with low concentration of Al₂O₃. The spectral parameters of ASB-II spectrum are g_| = 1.916–1.921; g_⊥ 1.980–1.988; A_| = (188?190) × 10^?4cm^?1 and A_⊥ = (74–77) × 10^?4cm^?1. Three intense bands at 370, 455 and 700 ans 720 nm observed in these glasses can be attributed to V³⁺ ions. The excellent agreement of the parameters of the EPR spectrum of V⁴⁺ ions in crystalline α-crystobalite AIPO₄ and ASB-II spectra in the glasses under study suggest the identical electron structure of the paramagnetic species. This species is believed to be characterized by optical bands at 680 and 790 nm which have been observed by de Biasi. The orbital mixing coefficients indicate strong tetragonal distortion of vanadyl complexes responsible for the ASB-II spectrum. It is assumed that VO²⁺ ions responsible for this spectrum act as modifiers fitting into the relatively small holes of the three-dimensional networks of phosphate glasses containing no cations of large radii. The microscopic basicity of oxygens in such holes must be about 0.48.     

Nuclear magnetic resonance studies of the glasses in the system K2OB2O3P2O5

B¹¹ NMR spectra have been used to study the structure of glasses in the system K₂OB₂O₃P₂O₅. The results indicate that the glasses do not contain an appreciable number of boron atoms in BO₃ units with one or two non-bridging oxygens. The fraction N₄ of boron atoms in BO₄ units is measured and analyzed according to a structural model containing the following elements. (1) If the binary borophosphate system forms glasses, they consist of a borophosphate (BPO₄) network and a borate network for K<1, or a borophosphate (BPO₄) network and a phosphate network for K>1, where K = mol.% P₂O₅/mol.% B₂O₃. (2) The conversion rates of BO₄ units (i.e. the rate of production or destruction by added oxygens) in the borate network and the borophosphate (BPO₄) network are given as (+2) and (?0.38), respectively. (3) K⁺¹ ions are proportionally shared between the two networks; (i.e. between the borate and borophosphate (BPO₄) networks for K<1, and between the phosphate and borophosphate (BPO₄) networks for K>1).