Reversible Optical Change of Amorphous Red Phosphorus in Reduced Phosphate Glasses

Amorphous red phosphorus formed in reduced phosphate glasses was found to show a photodarkening effect by illuminating the glasses with light approximately equivalent to its absorption edge; the optical transmission edge shifts toward longer wavelengths on illumination, and then a distinct deepening of the reddish color is observable visually. The photo-darkened specimen recovers its original transmission when it is heated at 300° to 350°C. This darkening-restoring process is confirmed to be reversible by repeated illumination and heating. Transmission measurements over a range of elevated temperatures suggest that this optical characteristic of red phosphorus is unique to its amorphous state.     

Bismuth Phosphate Glasses

Homogeneous glasses are formed in the Bi₂O₃-P₂O₅ system up to 35 mol% (63.8 wt%) Bi₂O₃. In property vs composition plots, the thermal expansion coefficient and tan δ exhibit minima, and hardness and activation energy for conduction show maxima at about 20 mol% Bi₂O₃. The deformation temperature of the glasses also increases abruptly at this composition. This anomalous behavior is interpreted in terms of a change in the function of Bi³⁺ ions from network formers to network modifiers.     

Constitution of Mixed-Alkali Phosphate Glasses: Constitution of Lithium-Rubidium Phosphate Glasses

In a previous study of the constitution of lithium-sodium-potassium phosphate glasses slight but definite cationic effects were observed. The constitution of lithium-rubidium phosphate glasses with , the number average chain length, varying from 1.25 to 9.00 was determined by paper chromatographic methods to follow the effect of substituting the rather large rubidium ion (1.47 A) for the small lithium ion (0.68 A). Systematic changes were observed; these changes, however, were numerically small. With the increase in the rubidium substitution for lithium the pyrophosphate content of the glass decreased and the tripolyphosphate content increased. Glasses with values as low as 1.5 (Li/Rb = 1/1) could be made by quenching the platinum crucible containing the melt in water. The = 1.25 glass, however, devitrified when thus made. It could be prepared only by the new copper-block-cooled strip furnace technique.     

Photoelastic Effects in Phosphate Glasses

The stress-optical coefficients of RO-Pz05 glasses (R = Mg, Ca, Sr, Ba, and Zn) were measured, and the photoelasticity mechanisms were analyzed based on the equation expressing the relation among the photoelastic constants, the elastic moduli, and the refractive index of glasses. No simple relation was found between the stress-optical coefficient and the elastic modulus, indicating that the factor (p – q), where p and q are the Neumann strain-optical coefficients, is important. The change of (p – q) with glass composition is governed mainly by changes in the effect of the atoms, rather than the lattice. The atomic effect increases with decreasing radius of the divalent cation, except for Zn²⁺. The ZnO-containing glasses exhibit extraordinarily large atomic effects. The photo-elasticity mechanism is discussed in relation to the nature of the chemical bonds.     

Ionic Conduction in Phosphate Glasses

Ionic conductivity in phosphate glasses has been known for almost 30 years. Recently these glasses have been shown to exhibit some of the highest ionic conductivities ever reported. In many cases, because of their ease of preparation, low melting points, strong glass-forming character, and simple composition, phosphate glasses have been studied more than any other ionically conducting glasses. However, no single review has ever been made of these glasses with the purpose of correlating the apparent widely disparate values of conductivity that these glasses exhibit. In this review, the conductivities of phosphate glasses are examined considering new structural studies of them. A systematic comparison of the dependence of the conductivity on glass chemistry reveals that, similar to other glass families (silicates and borates for example), the conductivity maximizes when the cation environments in the glass are minimized in their charge density and maximized in their site proximity.     

Constitution of Mixed-Alkali Phosphate Glasses: IV, Constitution of Lithium-Cesium Phosphate Glasses

The constitution of lithium-cesium phosphate glasses was determined by paper chromatographic techiques. Because of the rather high hygroscopicity, glasses with M/P ratio >1.33 could not be prepared. With increase in cesium/lithium ratio, the tripoly and tetrapoly fractions increased, indicating a definite cationic effect. The significance of the results is discussed.     

Free Volume of Phosphate Glasses

Free volume (V_f), defined by Simha and Boyer, was measured for glasses in the system MO-P₂O₅ (M=Be, Mg, Ca, Ba, Zn) and (1-x)MO·P₂O₅-xAl₂O₃·3P₂O₅ (M = Mg, Ca, Ba). Experimental V_f of the glasses was ∼0 to 0.3. These results indicate that V_f is not a universal constant (∼0.1) for all glasses as previously reported, but that V_f depends on the glass backbone structure.     

Constitution of Soluble Phosphate Glasses

Filter-paper chromatographic methods have been developed which permit the separation and de- termination of condensed phosphate anions containing up to four phosphorus atoms per ring and of linear structures containing from one to nine phosphorus atoms per chain. These methods have been used to study the anions produced when soluble sodium phosphate glasses of a range of compositions and methods of preparation are dissolved in water. The analyses are in qualitative agreement with the structure of phosphate glasses proposed by Van Wazer. X-ray and other evidence is presented which indicates, for the range of compositions studied, that the structures of condensed phosphate anions found in solution correspond to similar structures of condensed phosphates in the glass before dissolution and do not arise during the solution process. The study thus supports the polymer approach to the constitution of glasses for the range of com- position studied.     

Role of Iron in Calcium Phosphate Glasses

Some physical properties okf phosphate glasses con-taining up to about 26 mol% Fe₂O₂ were studied. Pronounced changes in properties were observed at compositions containingabout 6, 10, and 13 mol% Fe₂O₃. The X-ray diffraction spectra of devitrified (heat-treated) samples showed new compounds near these compositions. Electron spin resonance and optical studies confirmed the presence of Fe³⁺ and Fe²⁺ in both 4- and 6-coordination. An increase in total iron in these samples was associated with a decrease in the ratios Fe²⁺ 4-coordinated/Fe³⁺ 6-coordinated 6-coordinated and Fe³⁺ 4-coordinated/Fe³⁺ 6-coordinated up to about 2.0 mol% Fe₂O₃, as shown by the intensity of the optical absorption bands at about 2.0 and 1.0 μm and by the intensity of the ESR lines at g⋍4.2 and 2.0, respectively. Samples containing up to 4.3 mol% Fe₂O₃ showed an increase in Fe³⁺ concentration and a decrease in Fe²⁺ concentration after gamma irradiation. The electrical conductivity and activation energy decreased sharply with increasing Fe₂O₃ content.     

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.     

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.     

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.     

Electret Properties of Radiation-Charged Phosphate Glasses

The process of formation of a surface charge in phosphate glasses depending on polarization conditions is investigated. A relationship is established between the chemical composition of glass and its capacity for forming internal electric fields under radiation for glasses of type 0.50P₂O₅ – 0.45RO – 0.05R₂O₃.     

Conversion of Tetranary Borate Glasses to Phosphate Compounds in Aqueous Phosphate Solution

In our earlier work, it was found that particles of a ternary alkali-borate glass, containing either CaO or BaO, converted completely to a crystalline phosphate of calcium or barium when reacted in an aqueous phosphate solution at 37°C. The present work is an extension of our earlier work to investigate the conversion of tetranary borate glass with the composition 10Li₂O·10CaO·10(AeO or T₂O₃)·60B₂O₃ (weight percent), where Ae is the alkai-earth metal Mg or Ba, and T is the transition metal La, Sm, or Dy. In the experiments, particles of each glass (150–300 μm) were reacted in 0.25 M K₂HPO₄ solution with a starting pH of ∼9.0 at 37°C. Weight loss and pH measurements indicated that the reaction was complete after 30–50 h, yielding an amorphous product. X-ray fluorescence showed that the as-formed product consisted of a calcium phosphate phase that contained the alkali-earth metal or transition metal present in the starting glass. Heating the as-formed material for 8 h at 600°–700°C produced a mixture of two crystalline phosphates: calcium phosphate and an alkali-earth or transition metal phosphate. The kinetics and mechanism of converting tetranary borate glass to phosphate materials are discussed and compared with data from earlier work for the conversion of ternary borate glass.     

XAFS Investigation of Platinum Impurities in Phosphate Glasses

The coordination environments of Pt impurities in a ternary K-aluminophosphate (KAP) glass and commercial K,Mg-aluminophosphate (KMAP) laser glasses have been investigated by Pt L _III-edge X-ray absorption fine structure (XAFS) spectroscopy. Pt valence in the KAP glass depends on the melt preparation atmosphere. Pt⁴⁺ ions form in melts that are bubbled with oxygen, whereas metallic Pt particles form when these same samples are remelted in air. Residual chlorine in KMAP glasses has an effect on Pt bonding. In chlorine-free samples, Pt⁴⁺ ions are coordinated with ∼5.4 (8) oxygen atoms with an average distance of 2.02 (1) Å. For glasses with low chlorine contents (<200 ppm Cl), the Pt⁴⁺ ions have both O and Cl atoms in the first coordination shell. As the Cl concentration increases, the number of O nearest neighbors decreases and for Cl:Pt > 5, only Cl nearest neighbors are observed. Pt⁴⁺ ions in these latter glasses are coordinated by ∼5.5 (8) Cl atoms at an average distance of 2.27 (2) Å.     

Equilibrium Studies of Fe in Alkali Phosphate Glasses

The Fe²⁺-Fe³⁺ equilibrium in binary Na₂O-P₂O₅, glasses was studied by equilibrating glass melts at different temperatures in air. The enthalpy change (δH) of the reaction 1/2Fe₂O₃⇌FeO+1/4O₂ was calculated for 4 glasses. The results indicate that (1) the equilibrium shifts toward the oxidized state as the Na₂O content of the glass increases (plots of log ([Fe²⁺]/[Fe³⁺]) vs mol% alkali were linear) and (2) Δ H values for glasses of different composition are nearly equal but differ from the standard (calculated) value for the reaction. The experimental ΔH values were nearly equal to that for the reaction FePO₄→1/3 Fe₃(PO₄)²+ 1/6P₂O₅+1/4O₂, indicating that Fe forms phosphate or polyphosphate configurations in the Na₂O-P₂O₅ glasses. In certain of the glasses studied a faint-pink solid precipitated; its X-ray diffraction pattern indicated that its principal component is crystalline Na₂Fe¹¹¹P₃O₁₀.     

部分稀土掺杂磷酸盐玻璃发光性质分析

磷酸盐玻璃中单掺杂镱（Yb）、铒（Er）、钕（Nd）等稀土元素,对其光谱特性,荧光寿命,低温特性等将产生重要影响。也会改善杂质对磷酸盐玻离性能的影响。     

Preparation and Properties of Nitrogen-Doped Phosphate Glasses

Techniques for preparation and the properties of phosphorus oxynitride glasses produced from sodium metaphosphate and nitride compounds are reported. Properties reported include nitrogen content, dissolution rate in water, thermal expansion coefficient, softening point, glass transformation temperature, density, refractive index, microhardness, and infrared absorption.     

Leachability of Molybdenum from Ternary Phosphate Glasses

With a view to use glasses as a source of molybdenum, which is one of the micronutrients required by plants, a systematic study of the leachability of molybdenum from ternary phosphate glasses having molar compositions of 25MoO₃-25X50P₂O_s (where X = Li₂O, Na₂O, K₂O, CaO, B₂O₃, or SiO₂) was carried out. Leaching of molybdenum ions has been studied as a function of pH, which shows that leaching increases with increasing pH of the solutions. The concentration of molybdenum ions in the leachate decreases with increasing bond strength between nonbridging oxygen ions and the cations in glasses. Leaching increases with an increase in leaching time and decreases with an increase in the particle sizes of the glasses. P₂O₅ was also leached along with MoO₃. The leaching characteristics of P₂O₅ from the glasses are also reported.     

Gamma-Ray Induced Coloring of Some Phosphate Glasses

The changes in gamma-ray induced optical absorption in phosphate glasses resulting from changes in composition, conditions during melting, and additions of small amounts of some oxides are discussed. A resolution of the induced spectra showed that the observed absorption is due to the superposition of three bands at 2.3, 2.9, and 5.5 e.v. (540, 425, and 225 mü) and to a fourth band whose absorption peak is beyond 6 e.v. The ultraviolet induced absorption increases, whereas the visible absorption decreases in glasses melted under reducing conditions as opposed to those melted under normal conditions in air and on replacement of K⁺ by Na⁺ or Li⁺. A similar effect is produced on replacement of Ba⁺⁺ by Pb++ and on the addition of T1₂O to a CaO-P₂O₅ glass or the addition of As₂O₃ to a CaOP₂O₅, GeO₂ glass. Additions of large amounts of GeO₂ are accompanied by a decrease in the number of nonbridging oxygens and a decrease in the visible induced absorption. Replacement of Ca ⁺⁺ by Ba⁺⁺ ions showed an over-all decrease in the induced absorption. The addition of small amounts of the oxides of germanium, titanium, iron, thallium, niobium, and arsenic showed an appreciable effect in inhibiting the visible induced coloration.