Constitution of Sodium, Potassium, and Lithium Phosphate Glasses

The chain-length distributions in solutions of sodium phosphate glasses were reinvestigated using improved paper chromatographic techniques. The range of compositions was extended to glasses of higher Na/P ratios by using a through-flame technique for their preparation. The distributions obtained confirmed the earlier work with the exception that cyclic phosphates were found in solutions of glasses having or approaching the metaphosphate composition despite prolonged heating of the glasses in the molten condition. The earlier observation was that prolonged heating eliminated the cyclic phosphates. As before, no orthophosphate was found, as predicted by Van Wazer, and neither the Poisson nor the "random reorganization" distributions fitted the data for both high- and low-average chain lengths. Although some sort of rearrangement is occurring in the melt, it may not be a completely random process; a rapid change of chemical properties with chain length of the short polymers may have to be taken into account. This was confirmed by similar studies of potassium and lithium phosphate glasses, whose distributions were found to be different enough to demonstrate a cation effect. Consequently, more than stoichiometry is involved.     

Raman Spectra of Rare-Earth Phosphate Glasses

Raman spectra have been recorded for glasses in the binary systems CeO₂-P₂O₅ and Pr₂O₃-P₂O₅. The cerium phosphate glasses were prepared having different concentrations of CeO₂ and the praseodymium phosphate glasses with different ratios of Pr³⁺ to Pr⁴⁺. The spectra indicate that both cerium and praseodymium enter the glass in modifying sites. We see no changes in the Raman spectra with Pr³⁺/Pr⁴⁺ ratio. Measurements of the density and glass transition temperature are also reported.     

Constitution of Mixed-Alkali Phosphate Glasses: I, Constitution of Constant Lithium Variable Sodium-Potassium Phosphate Glasses

By the use of a mixture of alkali cations, Li, Na, and K, it has been possible to prepare phosphate glasses with higher M₂O/P₂O₅, ratio than was possible by the use of a single alkali cation. Variation of the Na:K ratio over a wide range has no effect on the distribution of polyphosphates in the composition range studied (Li: Na: K = 1:5:1 to 1:1:5). Glasses with × values of 2 or less contain an appreciable amount of orthophosphate ion. The significance of these results is discussed.     

Constitution of Mixed-Alkali Phosphate Glasses: II, Constitution of Variable Lithium Constant Sodium-Potassium Phosphate Glasses

In order to study the cationic influence of lithium, if any, the constitution of variable lithium constant sodium-potassium phosphate glasses was determined using paper chromatographic methods. It was possible to prepare glasses with very low ñ, the number average chain length value. Glasses with ñ values of 2, 1.75, and 1.5 could be prepared for glasses with Li:Na:K atomic ratios of 1:1:1 and 2:1:1. Attempts to prepare a glass with ñ= 1.25 were unsuccessful. At higher lithium concentrations, it was not possible to prepare glasses with low ñ values. The constitution of lithium phosphate glasses was reinvestigated. A comparison of the constitutions of mixed-cation phosphate glasses and lithium glasses indicates a small but definite cationic effect. The significance of these results in relation to Van Wazer's polymer theory and distribution laws is discussed.     

Effect of CoO and Gamma Irradiation on the Infrared Absorption Spectra of Lithium Borate Glasses

Undoped and cobalt-doped lithium borate glasses (LBG) of various compositions, by varying cobalt contents were prepared by a conventional melt quenching technique. The density and molar volumes of the glass samples were estimated and; infrared absorption spectra were measured in the spectral range 400–1600 cm^?1before and after an irradiation dose of 50 kGy and 200 kGy. Experimental results showed that the density of studied samples increased as CoO increased while the molar volume decreased. FT-IR spectra of the prepared samples have been analyzed by the deconvolution of the spectra. A deconvolution technique is presented to make use of the BO₄ data and follow the change in the modifier and former fractions of CoO. FTIR was also used to study the glass system before and after gamma irradiation. The experimental results clearly indicate that after irradiation a significant change in the structure of the LBG glass network is observed. The modifying action of CoO on the glass composition is also studied. The glasses doped with 5 wt% of CoO are relatively more radiation resistant than the other compositions.     

Infrared Spectra of a Water-Containing Glass

Infrared absorption was measured on an NajO-K₂O-ZnO-Al₂O₃-SiO₂ glass with up to ∼11 wt% water. Fundamental and overtone-combination bands were observed at 1.41, 1.91, 2.22, 2.87, and 6.1 μm. Molar absorptivities were determined for the hydrated glass for H₂O and OH levels using the molar absorptivity calculated for the 2.22-μm band in the as-melted glass. By this procedure the concentration of molecular water and OH groups could be determined separately. These results show that the OH content of the hydrated glass, as determined from the 2.22-μm band, is constant at >7 wt% H₂O; additional H₂O is attributed to molecular water only. Good agreement was found between these data and H₂O/OH molecular ratios obtained from NMR.     

Raman Spectra of Molybednum Phosphate Glasses and Some Crystalline Analogues

The Raman spectra of a series of glasses in the system MoO₃-P₂O₅ and the polyerystalline compounds molybdenum metaphosphate (MoO₂(P0₃)₂) and molybdenum pyrophosphate ((MoO₂)₂P₂O₂) are reported. The spectra indicate that traces of P=O and phosphate chains are present only in glasses having less than 50 mol% MoO₃. Comparison of the glass spectra with spectra of crystalline molybdenum phosphates indicates the presence of metaphosphate and orthophosphate structural groups of MoO₃ concentrations of about 50 mol% or less. As the MoO₃ concentration is increased, the bands characteristic of pyrophosphate groups appear in the spectra and become the dominant feature at 76 mol% MoO₃ concentration. Metaphosphate groups are present in the glass even at the highest MoO₃ concentrations measured.     

The Influence of Aluminum Oxide on the Thermal Expansion, Glass Transition Temperature, and Viscosity of Lithium and Sodium Aluminoborate Glasses

The glass transition temperatures and thermal expansion coefficients below and above the glass transition range are determined for lithium and sodium aluminoborate glasses over a wide range of concentrations. The temperature dependences of the viscosity for sodium aluminoborate and certain lithium aluminoborate glasses are studied in the viscosity range 10^10.5–10⁵ P. The data obtained are compared with the results of earlier investigations into the properties of barium aluminoborate glasses. The composition dependences of the properties studied are interpreted in the context of possible changes in the boron and aluminum coordination.     

Viscosities, Glass Transition Temperatures, and Microhardness of Y-Si-A1-O-N Glasses

Y-Si-A1-O-N glasses containing up to 15 at.% nitrogen were prepared. Comparisons of properties of glasses with the same cation composition but with varying N:O ratios show that glass transition temperature, viscosity, and microhardness all increase with increasing nitrogen content.     

Dielectric Relaxation Strength of a Low-Alkali Glass

The low-frequency dielectric loss maxima for glasses with low alkali concentrations are often obscured by a much larger dc conductivity contribution to the dielectric loss. Therefore, quantitative determination of the dielectric relaxation strengths for these glasses is difficult. An approximate relation between the impedance, electric modulus, and dielectric constant relaxation maxima is developed for glasses exhibiting small dielectric relaxation strengths. Using the obtained relations, the dielectric relaxation strength, Δe, for a GeO₂ glass containing 47 wt ppm Na₂O is estimated to be ≅0.3.     

Absorption Spectra of First-Row Transition Metal Ions in Glasses

Certain optical transitions were calculated for the first-row transition metal ions Ti³⁺, V³⁺, Cr³⁺, Fe²⁺ Co²⁺, and Ni²⁺ in a silicate matrix. The calculations were performed at 7 inter-ionic distances for each ion because the metal-ion-to-oxygen interionic distances are unknown; the silicate oxygen charge was varied from 1.00 to 2.00 in each case because the true charge on silicate oxygens is also unknown. Integrals used in the calculations were calculated using Slater and self-consistent field wave functions, and computer programs were used to evaluate all integrals. Equations were derived for calculating all optical transitions for these ions in octahedral fields; the extension to fields of other symmetry is trivial. Several optical transitions were computed to obtain the calculated orders of magnitude for the optical transition. The results for self-consistent field wave functions are lower than expected; they indicate that the transition metal ion in glasses is situated in fields near the size of aquo complexes.     

Coordination State of Boron and Aluminum in Low-Alkali Aluminoborosilicate Glasses

The structure of aluminoborosilicate glasses is considered. It is found that the coordination states of boron and aluminum in glasses may vary depending on the composition, which has a perceptible effect on the properties of glaze glasses. Significant discrepancies were found between the experimental and calculated TCLE values of such glasses, which is due to a changed content of four-coordination boron and the emergence of six-coordination aluminum. Considering these data, it is possible to predict the physicochemical properties of glaze glasses.     

Effect of Temperature Gradient on the Intensity of Light Scattering in Phosphate Glasses in the Glass Transition Range

A correlation between the peak of the intensity of light scattering and the temperature gradient arising across the sample after temperature jumps in the glass transition range is revealed from experimental data. Analysis of the experimental results shows that the peak of the intensity of light scattering is a quadratic function of the temperature gradient. The result obtained is in agreement with the predictions made from the theoretical analysis of the regularities observed in light scattering by nonuniformly heated liquids.     

Glass Transition and Crystallization of Glasses Based on Rare-Earth Borates

The glass formation is investigated and the highest contents of rare-earth oxides are determined in glasses of the Ln ₂O₃–B₂O₃ system in the composition region (Ln ₂O₃)_{1 + x} · 3B₂O₃ (Ln = La, Nd, Gd, Er, Dy, Yb, Lu; 0 x 0.8). It is shown that the total content of rare-earth oxides in the La₂O₃–Ln ₂O₃–B₂O₃ ternary system can substantially exceed their highest content in the binary systems. The devitrification of glasses in the La₂O₃–Ln ₂O₃–B₂O₃ system at temperatures above the glass transition point T _g is analyzed.     

Investigation of Structure of Glasses by Their Infrared Reflection Spectra

Infrared reflection spectra of a number of glasses are presented. It is apparent that in some cases such a method may be a useful tool in determining the atomic arrangement in glasses, especially when combined with quantitative measurements of the refractive index and extinction coefficient. The dispersion curves of barium-containing silicate glasses show that the network of these glasses contains metals in at least two different types of coordination. One is obviously the silica tetrahedron and the other is probably a octahedrally coordinated barium. The latter is concluded by comparison with the reflection spectrum of benitoite. Reflection spectra of boric oxide glasses are presented. These indicate that pure boric oxide glass is not 100% triangularly coordinated and that the pure glass contains much more tetrahedral coordination than was previously concluded from X-ray-scattering data.     

铁磷酸盐玻璃析晶的拉曼光谱及显微分析

为研究热效应对铁磷酸玻璃结构的影响,对40Fe2O3-60P2O5玻璃样品在600～800℃进行热处理,获得了结晶样品.利用XRD、Raman等研究了玻璃结晶化过程中的结构变化,指认了铁磷酸盐玻璃微结构的振动模式的归属.结果表明,在600℃,铁磷酸盐玻璃析出的结晶相主要为:Fe(PO3)3和Fe4(P2O7)3,在700℃、800℃玻璃析出的结晶相主要为Fe4(P2O7)3.利用SEM观察了玻璃样品的微观形貌,结晶相的微观形貌为片状,保温时间延长,片层厚度增加.     

On the Structure of Low-Alkali Rubidium and Cesium Borate Glasses and Melts

The structure of low-alkali rubidium and cesium borate glasses and melts at temperatures from the glass transition points of the initial glasses to 1000–1100°C is studied by the small-angle X-ray scattering (SAXS) technique. It is found that, over the entire temperature range under investigation, the melts have a microinhomogeneous structure. A decrease in the melt temperature leads to an increase in the sizes of inhomogeneity regions, which is caused by the Ostwald ripening. The sizes remain unchanged at temperatures in the vicinity of the liquidus temperature (in the range of approximately ±50 K). The temperature dependences of the inhomogeneity density are determined at low temperatures. It is demonstrated that, at temperatures close to the glass transition point of the inhomogeneity regions, their density decreases with a decrease in the temperature.