INFLUENCE OF GLASS COMPOSITION ON REDUCIBILITY OF Ag+, Bi3+, Sb3+, AND PP+*

The reducibility of a number of ions by dry hydrogen was studied in various glass compositions. Reduction temperatures with dry hydrogen were about 75° C, lower than with wet hydrogen. The glasses contained 5.0% of Sb₂O₃, Bi₂O₃, or PbO or 0.1% of Ag₂O. In all of the glasses, silver ions were reduced at lower temperatures as basicity was increased, while an increased ratio of B³⁺ to O^2- or Si⁴⁺ to O^- increased stability. The reducibility of Bi³⁺, Sb³⁺, and Pb²⁺ are not easily interpreted. Silver showed reduction at approximately 130°C., bismuth at 200°C., lead at 350°C., and antimony at 400°C.     

THE EFFECT OF BORIC OXIDE ON THE DEVITRIFICATION OF THE SODA-LIME-SILICA GLASSES. THE QUATERNARY SYSTEM,Na2O-CaO-B2O3-SiO21

Commercial glasses of the soda-lime-silica types do not consist solely of these three oxides, but in addition contain significant amounts of other constituents which arc introduced incidentally as impurities or deliberately for some beneficial influence. Such minor additions may have either a favorable or unfavorable influence on the tendency of the glass to devitrify, and an investigation into the effect of such minor components is desirable. Previous results with MgO and with A1₂O₃ have shown that a systematic study of a four-component system is necessary to the understanding of its devitrification relations, and that arbitrary and fragmentary excursions into such a system give little insight into the general effect of the minor constituent and may be misinterpreted to erroneous conclusions as to the effect of this constituent on glasses of slightly different composition. Accordingly, in taking up the study of the effect of B₂O₃ on the devitrification of the soda-lime-silica glasses, it was added to 21 glasses in and near the field of devitrite, Na₂O·3CaO·6SiO₂, in the ternary system, Na₂O–CaO-SiO₂, in amounts up to about 5%. In all cases the liquidus temperature was lowered, and the tendency toward devitrification reduced. Both of these effects are desirable and add to the thermal stability of the glass. With glasses containing 10% CaO, initially in the field of tridymite or so near to it that a small addition of B203 brings the resulting glass into the tridymite field, this initial lowering is replaced by an increase in the liquidus temperature which passed through a maximum at from 4 to 6% B₂O₃. With all other glasses the lowering continues, and the rate of decrease is greatest with glasses originally in the field of Na₂O·2CaO·3SiO₂. An exploration of the quaternary system showed that no new compounds are formed in any mixture that can be obtained by adding B203 in amounts up to 50% to any mixture in or near the devitrite field. It also indicated the probability that a narrow band of immiscible liquids is formed, extending across the ternary system, CaO-B₂O₃–SiO₂, and including the mineral danburite, CaO·B₂O·2SiO₂, but probably not extending far into the quaternary system. The fields of wollastonite and of Na₂O·2CaO·3SiO₂ were found to sweep out regions in the quaternary system extending over the square, Na₂O·SiO₂-Na₂O·B₂O₃-CaO-B₂O₃-CaOSO₂, and the field of Na₂O·CaO·SiO₂ was found to extend over the middle of this square, and is probably adjacent to the fields of wollastonite and of Na₂O· 2CaO·3SiO₂. A compound is formed between Na₂O·B₂O₃ and CaO·B₂O₃. There is included a general survey of the literature relative to the effect of B203 on the properties of glass.     

Enhancement of the radiation resistance of cerium-containing fluorophosphate glasses through codoping with Sb2O3 and Bi2O3

The growing demand for radiation-resistant optical glasses for space and nuclear radiation applications has attracted significant research interest. However, radiation-resistant fluorophosphate glasses have been poorly studied. In this work, we report on the tailoring and performance of radiation-resistant fluorophosphate glasses that contained cerium through codoping with Sb₂O₃ and Bi₂O₃. The physical properties, optical properties, microstructure, and defects of fluorophosphate glasses were investigated using transmittance measurements, absorption measurements, as well as Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR) spectroscopy. The results showed that the radiation resistance of all codoped fluorophosphate glasses was better than the undoped cerium-containing fluorophosphate glasses after 10–250 krad(Si) irradiation. Especially in glasses doped with Bi₂O₃, the optical density increment at 385 nm was only 0.1482 after 250 krad(Si) irradiation. The CeO₂ prevented the development of phosphate-related oxygen hole center (POHC) defects, whereas further codoping with Bi₂O₃ suppressed the formation of oxygen hole center (OHC) and POEC defects, reducing the breaking of phosphate chains caused by CeO₂. Bi³⁺ is more likely than Sb³⁺ to change the valence, affecting the transition equilibrium of intrinsic defects and reducing the concentration of defects produced by irradiation. When codoping with Sb₂O₃ and Bi₂O₃, Bi₂O₃ does not enhance radiation resistance owing to the scission effect of Sb₂O₃ on the phosphate chain, which is not conducive to the radiation resistance of glasses. This indicates that the cerium-containing fluorophosphate glasses doped with Bi₂O₃ can effectively suppress the defects caused by irradiation and improve the radiation resistance of the glasses.     

EFFECT OF COMPOSITION AND TEMPERATURE ON SOLUBILITY OF IRON OXIDE IN GROUND-COAT ENAMEL GLASS*

The solubility of iron oxide in ground-coat enamel glasses at various temperatures was studied by adding varying amounts of ferric oxide to the milled enamel and giving the mixture a heat-treatment to acquire uniformity without devitrification at the desired temperature. The iron oxide solubility was obtained by finding the breaking point in the curve for iron oxide versus index of refraction. The frit solubilities were obtained at 1400°, 1600°, 1800°, and 2000°F. with variations in Na₂O, B₂O₃, A1₂O₃, CaF₂, CaO, F₂, SiO₂, COO, NiO, MnO₂, BaO, and MoO₃. Data are given on a number of commercial frits.     

Influence of Bi2O3/WO3 substitution on the optical,mechanical, chemical durability and gamma ray shielding properties of lithium-borate glasses

Six different lithium bismuth boro-tungstate glasses with chemical composition 20Li₂O-(20-x)Bi₂O₃-xWO₃-60B₂O₃ (x = 0, 1, 2, 3, 4 and 5 mol%) were produced by the quenching method. Then, the glasses were investigated by means of their optical, mechanical, chemical durability and gamma ray shielding properties. Measured values of density and ultrasonic velocities were used to determine the elastic properties of the glasses. The optical band gap determined using the absorbance spectrum fitting (ASF) model was found to decrease under Bi₂O₃/WO₃ substitution. The presence of BO₃, BO₄, BiO₆, and WO₄ structural groups in the glasses was confirmed by Fourier transform infrared spectroscopy (FTIR). The dissolution rate in the glass 20Li₂O–15Bi₂O₃–5WO₃–60B₂O₃ (LBWB5) was found to be 10 times lower than 20Li₂O-20Bi₂O₃– 60B₂O₃. Mass attenuation coefficients (MAC) values of the produced glasses were determined using the MCNPX Monte Carlo code and Phy-X/PSD program. The photon attenuation parameters such as half value layer (HVL), mean free path (MFP), effective atomic number (Z_eff), exposure buildup factor (EBF) and energy absorption buildup factor (EABF) were also studied. The obtained results showed that Bi₂O₃/WO₃ substitution has a direct impact on the photon attenuation abilities of produced glasses. More specifically, HVL values increased from 0.252 × 10^?2 cm for LBWB0 glass to 0.275 × 10^?2 cm for LBWB5 glass. However, different trends were observed for the photon buildup factors for the produced glasses. It can be concluded that the produced glasses have promising structural, optical, and photon attenuation properties to be used for gamma shielding applications.     

DIELECTRIC LOSS OF GLASS AT HIGH FREQUENCIES*

Power factor measurements at frequencies of 100, 500, 1500, and 5000 kilocycles were made on a series of soda-lime-silica glasses and on another series of glasses, starting with a base glass of the composition of 17.4% Na₂O, 10.1% CaO, 72.5% SiO₂ (or 1.4 Na₂O to 0.9 CaO to 6.0 SiO₂), to which 0.030 gram-atom of various elements in the form of their oxides were added. In the first series, the power factor for all glasses measured decreased with increasing frequency and increased markedly with increase in Na₂O content. In the second series, the power factor decreased with increasing frequency as in the case of the first series. An increase in power factor was produced by additions of Zr, Na, and Al oxides, and a decrease was produced by additions of the oxides of Si, V, Zn, Mg, B, Ti, Co, Ca, Ce, Ni, Mn, Fe, Ba, Pb, Li, and K.     

Concentration dependence of electric conductivity for fluorine-containing sodium borate glasses

The influence of sodium fluoride additives on the physicochemical properties of glasses in the Na₂O-B₂O₃ systems is investigated. The introduction of sodium fluoride into the Na₂O · 2B₂O₃ and Na₂O · 3B₂O₃ glasses leads to an increase in the electric conductivity. The temperature-concentration dependence of the electric conductivity has been investigated. It is shown that, in glasses of the NaF-Na₂O · 2B₂O₃ system, an increase in the volume concentration of sodium ions from 2.4 × 10⁻² to ∼3 × 10⁻² mol/cm³ is accompanied by an insignificant decrease in the activation energy E_σ from 1.44 to 1.38 eV and a sharp (by a factor of ∼30) increase in the electric conductivity. In glasses of the NaF-Na₂O · 3B₂O₃ system, an increase in the concentration of sodium ions from 1.8 × 10⁻² to ∼2.3 × 10⁻² mol/cm³ brings about an increase in the electric conductivity by a factor of approximately 100 and an increase in E_σ from 1.6 to 1.83 eV. A further increase in the concentration of sodium ions (up to 2.5 × 10⁻² mol/cm³) virtually does not affect the electric conductivity and E_σ. At the same concentration of sodium ions (∼2.46 × 10⁻² mol/cm³) in the 9.8NaF · 90.2[Na₂O · 2B₂O₃] and 57.1NaF · 42.9[Na₂O · 3B₂O₃] glasses, the electric conductivity and the activation energy are considerably higher in the glass with a larger fluorine content. The regularities revealed are interpreted in the framework of the microinhomogeneous glass structure.     

Concentration dependence of electric conductivity for fluorine-containing sodium borate glasses

The influence of sodium fluoride additives on the physicochemical properties of glasses in the Na₂O-B₂O₃ systems is investigated. The introduction of sodium fluoride into the Na₂O · 2B₂O₃ and Na₂O · 3B₂O₃ glasses leads to an increase in the electric conductivity. The temperature-concentration dependence of the electric conductivity has been investigated. It is shown that, in glasses of the NaF-Na₂O · 2B₂O₃ system, an increase in the volume concentration of sodium ions from 2.4 × 10⁻² to ∼3 × 10⁻² mol/cm³ is accompanied by an insignificant decrease in the activation energy E_σ from 1.44 to 1.38 eV and a sharp (by a factor of ∼30) increase in the electric conductivity. In glasses of the NaF-Na₂O · 3B₂O₃ system, an increase in the concentration of sodium ions from 1.8 × 10⁻² to ∼2.3 × 10⁻² mol/cm³ brings about an increase in the electric conductivity by a factor of approximately 100 and an increase in E_σ from 1.6 to 1.83 eV. A further increase in the concentration of sodium ions (up to 2.5 × 10⁻² mol/cm³) virtually does not affect the electric conductivity and E_σ. At the same concentration of sodium ions (∼2.46 × 10⁻² mol/cm³) in the 9.8NaF · 90.2[Na₂O · 2B₂O₃] and 57.1NaF · 42.9[Na₂O · 3B₂O₃] glasses, the electric conductivity and the activation energy are considerably higher in the glass with a larger fluorine content. The regularities revealed are interpreted in the framework of the microinhomogeneous glass structure.     

ANALYSIS OF RECENT MEASUREMENTS OF THE VISCOSITY OF GLASSES.—II1

Viscosity of two series of four component glasses .—The results recently reported by S. English² are here analyzed by the method used in a previous paper.³ (1) Series 6SiO₂, 1.2Na₂O, 0.8(CaO+MgO). The temperature at which the difference between the viscosity of a glass and the viscosity of 6SiO₂,2Na₂O at the same temperature makes a sharp bend is called the aggregation temperature Ta . It seems to correspond to the devitrification temperature. For this series Ta reaches a sharp minimum for the composition 6SiO₂, 1.15Na₂O, 0.45MgO, 0.39CaO. The viscosity for any temperature also reaches a minimum at or near this composition. (2) Series 6SiO₂, 1.1Na₂O, 0.9(CaO+Al₂O₃). The curves are similar to those for the first series, TA reaching a sharp minimum for the composition 6SiO₂, 1.11Na₂O, 0.81Ca0, 0.14Al₂O₃.     

Mössbauer spectroscopy,XRPD, and SEM study of iron-containing Na2O-B2O3-SiO2 glasses

Glasses in the Na₂O-B₂O₃-SiO₂-Fe₂O₃ system are suitable for producing magnetic porous glasses—host matrices for multiferroic composite materials for spintronics applications. Successful synthesis of such materials is dependent on the knowledge of crystallization and immiscibility areas in this system. Here, we report new findings for such glasses with a constant SiO₂ concentration of 70 mol %, containing 7-12 mol % Fe₂O₃, whose compositions lie in the low (2 mol % Na₂O) and higher (8-12 mol % Na₂O) alkali regions, heat-treated at 550°C. Glasses were studied using analytical chemistry methods and investigated by means of Mössbauer spectroscopy, XRPD and SEM. We outlined the immiscibility area boundary in the chosen silica cross-section for 550°C, indicating the region of interconnected morphology and the crystallization fields of magnetite and FeSiO₃, and correlated them with data on the valence and coordination state of iron in glasses. We find that both Fe³⁺ and Fe²⁺ ions in the low-alkali region are octahedrally coordinated, in higher alkali area Fe³⁺ and Fe²⁺ are tetrahedrally and octahedrally coordinated, respectively. A significant amount of Fe²⁺ in the low-alkali region can be the cause of the FeSiO₃ formation. The usual crystalline phase in non-X-Ray amorphous glasses is magnetite, precipitating at the annealing stage.     

SOME RELATIONS OF COMPOSITION TO SOLUBILITY OF ENAMELS IN ACIDES1

Review of literature.—The literature on acid resisting enamels and glasses is reviewed. Acid resisting powers produced by different oxides.—When substituted one for another, in each case in equal percentage amounts, various oxides and minerals increased the resistance of various enamels to the action of boiling 20 per cent hydrochloric acid in the following order of effectiveness: Al₂O₃, cryolite, Na₂O, PbO, BaO, Li₂O, MgO, CaF₂, ZnO, SrO, CaO, B₂O₃. The first five mentioned were especially effective. The remainder are undesirable materials from the standpoint of acid resistance. Effect of the enamel base.—The relative effects of the materials were the same for various base enamel compositions. Effect of ZrO₂ and TiO₂. —ZrO₂ and TiO₂, when substituted for small amounts of SiO₂, increased the resistance of various enamels to attack by acids, ZrO₂ being most effective in this respect. The favorable action of ZrO₂, is offset by a tendency to produce excessive chipping. Rutile gives less chipping than either zirconia or silica and greater acid resistance than silica. Best compositions.—Enamels 2,17,19,26,27, and 33 of table 1 showed resistance to action of the acid equivalent to that of the original competitions based on the analysis of a French acid-resisting enamel. By use of the data developed in this investigation other highly acid-resisting compositions can readily be formulated.     

Statistical mechanical model for the formation of octahedral silicon in phosphosilicate glasses

Unlike ambient pressure silicate glasses, some phosphosilicate glasses contain sixfold-coordinated silicon (Si⁶) units even when prepared at ambient pressure. The variation in the fraction of Si⁶ with composition remains a topic of interest, both for technological applications of phosphosilicate glasses and for fundamental understanding of the glass structure. In this work, we use statistical mechanical modeling to predict the composition–structure relationships in Na₂O–P₂O₅–SiO₂ and CaO–P₂O₅–SiO₂ glasses. This is achieved by accounting for the enthalpic and entropic contributions to the interactions between each pairwise modifier ion and structural unit. The initial enthalpy parameters are obtained based on experimental structural data for binary Na₂O–SiO₂, CaO–SiO₂, Na₂O–P₂O₅, and CaO–P₂O₅ glasses, which can then be transferred to predict the structure of mixed former glasses. This approach has previously been used to predict the short-range structure of borosilicate and aluminoborate glass systems. However, here we show that the formation of Si⁶ must be specifically included to make accurate predictions of the composition–structure relationships in phosphosilicate glasses. After incorporating the formation mechanism of Si⁶ in the statistical mechanics model, we find an excellent agreement between model predictions and experimental structure data for Na₂O–P₂O₅–SiO₂ and CaO–P₂O₅–SiO₂ glasses.     

STUDY OF THE PROPERTIES OF SIMPLE ENAMEL GLASSES1

Three component glasses of the systems Na₂–B₂O₃–SiO₂ and Na₂O–PbO–SiO₂ were investigated as to acid-resisting properties. An increase in silica in general improves the acid resistance. The effect of Na₂O, B₂O₃, and PbO on the acid resistance of an enamel is dependent on the composition to which these oxides are added. Some of these enamels showed considerable promise as acid-proof enamels.     

Properties and Crystallization Behavior of Sodium Iron Phosphate Glasses

Ternary Na₂O–Fe₂O₃–P₂O₅ (NFP) glasses with varying Na₂O/Fe₂O₃, Na₂O/P₂O₅, and Fe₂O₃/P₂O₅ ratios were prepared. The properties and crystallization tendencies were systemically investigated. It is shown that both density and chemical stability of the glass increase with Fe₂O₃. In contrast the Na₂O/P₂O₅ ratio has little effect on the glass properties for a fixed Fe₂O₃ content. The crystallization behavior of the glasses was analyzed by DTA and XRD. Unlike Li₂O–Fe₂O₃–P₂O₅ glasses NFP glasses were found to be stable against crystallization. 15Na₂O–27Fe₂O₃–58P₂O₅ glass was found to have the highest chemical stability among the studied NFP samples; the influence of TiO₂, ZrO₂ on crystallization in this composition was studied. It is found that addition of 3.4 mol% TiO₂ or 2.2 mol% ZrO₂ had little effect on the crystallization behavior of this glass. However, when the amounts of TiO₂ or ZrO₂ were increased to 8.4 or 5.5 mol% respectively the glass readily devitrified. Furthermore the addition of fluorine (introduced by replacing Na₂CO₃ with NaF in the glass batch) leads to amorphous glasses which could be crystallized to form NaFeP₂O₇ upon controlled thermal treatment. With increasing NaF additions the activation emergy for crystallization decreased from 428 to 381 kJ/mol.     

Submixture model to predict nepheline precipitation in waste glasses

High-alumina high-level waste (HLW) glasses are prone to nepheline precipitation during canister-centerline cooling (CCC). If sufficient nepheline forms, the chemical durability of the glass will be significantly impacted. Overly conservative constraints have been developed and used to avoid the deleterious effects of nepheline formation in U.S. HLW glasses. The constraints used have been shown to significantly limit the loading of waste in glass at Hanford and therefore the cost and schedule of cleanup. A 90-glass study was performed to develop an improved understanding of the impacts of glass composition on the formation of nepheline during CCC. The CCC crystallinity data from these glasses were combined with 657 glasses found in the literature. The trends showed significant effects of Na₂O, Al₂O₃, SiO₂, B₂O₃, CaO, Li₂O, and potentially K₂O on the propensity for nepheline formation. A pseudo-ternary submixture model was proposed to identify the glass composition region prone to nepheline precipitation. This pseudo-ternary with axes of SiO₂ + 1.98B₂O₃, Na₂O + 0.653Li₂O + 0.158CaO, and Al₂O₃ was found to divide glasses that precipitate nepheline during CCC from those that do not. Application of this constraint is anticipated to increase the loading of Hanford high-alumina HLWs in glass by roughly one-third.     

SHORT METHODS FOR CHEMICAL ANALYSIS OF GLASS*

Analytical methods have been developed which shorten the time required for the determination of many of the constituents found in glass. These short methods have been worked into a procedure for the routine chemical analysis of container and sheet glasses. The determination of SiO₂, BaO, SO₃, R₂O₃, CaO, MgO, B₂O₃, Na₂O, and K₂O percentages on several samples can be made in a single day. Most of the experimental work has been done on Bureau of Standards glass No. 128, but results from several other glasses are included. Particular care has been taken to discover interfering substances and to eliminate errors from this source. The accuracy is comparable with that obtained from the use of umpire methods.     

A closer-look on Copper(II) oxide reinforced Calcium-Borate glasses: Fabrication and multiple experimental assessment on optical,structural, physical,and experimental neutron/gamma shielding properties

This study aimed to fabricate six different Copper(II) oxide reinforced Calcium-Borate glasses with different types of substitutions such as Al₂O₃/V2O₅, BaO₂/V₂O₅, and ZnO/V₂O_5. Accordingly, a depth characterization process has been performed for ACV, BCV and ZCV glasses with a nominal composition of 55B₂O₃–35CaO–9Al₂O₃-0.5CuO-0.5V₂O₅, 55B₂O₃–35CaO-8.5Al₂O₃-0.5CuO–1V₂O₅, 55B₂O₃–35CaO–9BaO₂-0.5CuO-0.5V₂O₅, 55B₂O₃–35CaO-8.5BaO₂-0.5CuO–1V2O5, 55B2O3–35CaO–9ZnO-0.5CuO-0.5V2O5, 55B2O3–35CaO-8.5ZnO-0.5CuO–1V₂O₅. Optical, structural, physical, and experimental neutron/gamma shielding properties of synthesized glasses were determined, respectively. Experiments measuring neutron exposure indicated how well glass samples attenuated fast neutrons. The RADACS software was used to record data from a BF3 gas proportional detector from the Canberra NP-100B series and a 241Am/Be neutron source with a 10 mCi activity. The absorption edge belonging to the samples are found between 420 nm and 480 nm. Our findings showed that the optical band gaps for the samples ranged from 1.179 to 2.022 eV. The wavenumber range of 400–1600 cm^-1 was evaluated for the resulting peaks. The region with the highest band formation was approximately 760–1170 cm^-1. While BCV0.5 and BCV1 glasses with 9% and 8.5% BaO₂ insertion have the largest MAC values ranging between 2.255–0.076 and 2.156–0.076 cm²/g, the lowest MAC values varying between 0.361–0.0761 and 0.366–0.076 cm²/g belong to ACV0.5 and ACV1 glasses with 9% and 8.5% Al₂O₃ addition. Our results showed that the BCV glass family has superior material properties among the fabricated glasses. It can be concluded that BaO₂/V₂O₅ glasses may be used in replacement of Copper(II) oxide glasses to provide monotonic behavior on crucial characteristics while maintaining the greatest density increase for large gamma ray shielding properties.     

Influence of Cr3+ on yellowish-green UC emission and energy transfer of Er3+/Cr3+/Yb3+ tri-doped zinc silicate glasses

In this paper, we study the influence of Cr³⁺ on yellowish-green upconversion (UC) emission and the energy transfer (ET) of Er³⁺/Cr³⁺/Yb³⁺ tri-doped in SiO₂–ZnO–Na₂O–La₂O₃ (SZNL) zinc silicate glasses under excitation of the 980 nm laser diode (LD). The influence of Cr³⁺ on enhancing the red UC emission of Er³⁺/Cr³⁺/Yb³⁺ tri-doped in SiO₂–ZnO–Na₂O–La₂O₃ zinc silicate glasses under the excitation of 980nm LD was also investigated. The ET processes between Yb³⁺, Cr^3+, and Er³⁺, together with the combination of Yb³⁺-Cr³⁺-Er³⁺, which led to the green UC emission intensity of Er³⁺/Cr³⁺/Yb³⁺ tri-doped in SiO₂–ZnO–Na₂O–La₂O₃ zinc silicate glasses bands centered at ~546 nm have been significantly enhanced. By increasing the concentration of Cr³⁺ from 0 up to 5 mol.%, we can locate the Commission Internationale de l'éclairage (CIE) 1931 (x; y) chromaticity coordinates for UC emissions of Er³⁺/Cr³⁺/Yb³⁺ tri-doped in the central position of the yellowish-green color region of CIE 1931 chromaticity diagram. Besides, the ET processes between the Yb³⁺, Cr³⁺, and Er³⁺ are also proposed and discussed.     

Studies in Lithium Oxide Systems: I, Li2O B2O3–B2O3

Phase relationships in the system Li₂O, B₂O₃-B₂O₃ were studied by the quenching method using twenty compositions. The crystalline phases encountered were (a) Li₂O, B₂O₃, which melts congruently at 849°± 2°C., (b) Li₂O.-2B₂O₃, which melts congruently at 917°± 2°C., (c) a new compound, 2Li₂O-5B₂O₃, which melts incongruently at 856°± 2°C. and dissociates below 696°± 4°C., (d) Li₂O.3B₂O₃, which melts incongruently at 834°± 4°C. and dissociates below 595°± 20°C., and (e) probably Li₂O.4B₂O₃, which melts incongruently at 635°± 10°C. Reactions were sluggish at temperatures near 600°C., resulting in metastable relations. Hence phase equilibrium data relating to the lower stability limit of Li₂O.3B₂O₃ and to the upper stability limit of Li₂O.4B₂O₃ are considered to be tentative. Properties of the glasses and crystalline phases were studied. The refractive index of the glasses increased with the addition of Li₂O up to 22%, but further additions up to 40% had no substantial effect. Glasses containing less than 30% Li₂O were water soluble. Limited data on the density and thermal expansion of the glasses are presented. Li₂OB₂O₃ was euhedral, lath-shaped, length-fast, biaxial negative (2V = 27°), with n_α= 1.540, n_β= 1.612, n_γ= 1.616. Li₂O.2B₂O₃ was uniaxial negative, with n_e= 1.560, n_w= 1.605. Li₂O.3B₂O₃ was biaxial negative (2V = 75° to 80°), with n_α= 1.576, n_β= 1.602, n_γ= 1.605. X-ray powder diffraction data for the five crystalline compounds are presented. Thermal expansion data for Li₂O-B₂O₃ and Li₂O.2B₂O₃ and limited data on the fluorescent properties of the compounds are given. X-ray diffraction data are also presented for Li₂O.B₂O₃.4H₂O and Li₂O.-5B₂O₃. 10H₂O. Li₂O B₂O₃ was obtained by heating the first hydrate at 450° to 680° C. X-ray diffraction showed Li₂O.4B₂O₃ and Li₂O-3B₂O₃ to be the crystalline products obtained during heating the decahydrate at 500°C. and 600°C., respectively.     

CERAMIC ABSTRACTS SECTION

Data are presented on the properties of twenty-seven Na₂OSrO. Al₂O₃.SiO₂ glasses covering the following percentage composition ranges: SiO₂ 66 to 78; SrO 4 to 16; Al₂O₃ 0,2, and 4; and Na₂O 14, 15.5, and 17. The effects of the systematic substitution of SrO for SiO₂, A1₂O₃, and Na₂O are shown for liquidus temperature, viscosity, coefficient of expansion, deformation temperature, density, and resistance to dilute acid and distilled water. Comparisons are shown between these SrO glasses and corresponding CaO glasses for those properties previously described.