Three-component Glasses Research Articles

Role of short range order on crystallization of tectosilicate glasses: A diffraction study

The relationship between glass structure and crystallization behavior has remained elusive, though a general solution would have broad applications. In this work, three-component glasses were studied in the system MTSixO2x+2, where M = Na, Li, or Ca, T = Al, B, or Fe, and x = 1, 2, and 3. These glasses, selected to systematically explore network and modifier substitutions, included mineralogically important silicate chemistries (i.e., albite, jadeite, carnegieite, nepheline, anorthite, eucryptite, spodumene, aegirine, reedmergnerite, malinkoite). Glasses were interrogated using neutrons and synchrotron X-rays, and empirical potential structure refinement (EPSR) modeling was performed to compare the average glass structures to the analogous crystalline references. Through EPSR modeling, it was shown that similarity in the coordination number of the non-network cations in glass systems (i.e., alkali and alkaline earth) predicts which glasses easily crystallize an isochemical phase during cooling from melt. Average coordination number of the M and T type cations of glass versus isochemical crystal is proposed as a metric to predict crystallization. This metric is compared to other proposed metrics such as normalized temperatures, change in density, fragility, and thermodynamic parameters. This the first study to employ EPSR modeling to relate crystallization propensity of isochemical crystals to network modifier short-range order.

Hermetic glass sealing of AlN packages for high temperature applications

In this study the feasibility of glass soldering of aluminium nitride (AlN) for the package of silicon carbide semiconductors with application temperatures up to 600°C was evaluated. The components used were various commercially available solder glasses and a crystallising three-component glass. Chemical compatibility between the glass and AlN was investigated by means of both thermodynamic calculations and experimental work on solder joints. The PbO-free three-component glass was stable against AlN. Lead oxide containing glasses showed deleterious reaction with AlN, which can be inhibited by a passivating layer. Additionally the influence of the processing parameters atmosphere and mechanical pressure was investigated. Hermeticity of sealed packages could be proved for three glasses allowing high temperature application between 500 and 600°C.

Luminescence and guided-optics in Er-doped glass and GaAs films

We investigated luminescence properties of highly Er-doped silicate glass films prepared from doped silicate targets using RF magnetron sputtering technique. The Er-doped films show a strong, room-temperature luminescence at 1.54 urn wavelength. Fluorescence decay lifetime of up to 9 ms was obtained with the three-component glass. A strong correlation was observed between the lifetime and the melting temperature of glass over a broad range of host composition. The results indicate that network modifiers, such as sodium ions, soften the silica glass network and thus alleviate formation of Er pairs or clusters. The Er-doped thin-film waveguides fabricated on thick-oxide-grown silicon substrates show a propagation loss of less than 1 dB/cm. The relation of optical to electronic properties of Er-doped GaAs is modeled.

Optical losses from compositional fluctuations in three-component glasses

Abstract In a previous paper, the theoretical possibility of reducing optical losses in fused silica by minor additions of an alkali metal oxide was considered. The problem concerns a competition between density fluctuation losses (which decrease on addition of the modifying component) and compositional fluctuation losses (which increase, due to a tendency towards subliquidus phase separation). In order to combat the latter disadvantage, it is desirable to probe the effects of an addition of a second minor constituent, such as Al 2 O 3 , which tends to reduce the forces driving the phase separation. However, an explicit theory of concentration losses in a three-component glass that is capable of making quantitative predictions has never yet been presented. As a preliminary to the primary goal of finding the optimum additives for reducing total losses in the above context, such a formal theory is set out in this paper, and its accuracy tested by comparison with existing scattering measurements on some sodium aluminosilicate glasses.

Structural and valence state of iron ions in sodium-aluminum-phosphate glass

(SAP) glass by means of electron paramagnetic resonance (EPR), M6ssbauer spectroscopy (MS), and nuclear magnetic resonance (NMR). Our results enabled us to determine the characteristics of the occupancy and distribution of iron ions over tetra- and octahedral positions as a function of the ratio of the concentration of iron and aluminum oxides, to determine the concentration of Fe 3+ and Fe 2+ ions and the number of phosphorus and aluminum atoms in the nearest-neighbor environment of the impurity iron ions, as well as to estimate the effect of the concentration of aluminum oxide on the average distance between the phosphorus atoms in the SAP glass. Experimental Conditions. To synthesize the SAP glasses, we prepared a charge consisting of powders of the pure reagents NaPO3, AI203, and NaNO 3. The charge was held at 1100~ in an alundum crucible for 4 h in air to obtain frits of three-component glass, corresponding to the following oxide composition (mass %): 25 Na20-(10-21)AIxO 3-(5363)P205. The frit was mixed with Fe203 powder and held at 1050~ for 6 h, after which the melt was allowed to cool in air to room temperature within 3 h. The samples of SAP glass contained from 0.4 to 6 mass % Fe203. The EPR, M6ssbauer, and NMR spectra were recorded using glass powders with grain size not exceeding 120/zm; all measurements were performed at room temperature. The EPR spectra of the Fe 3 + ions were recorded on a RI~- 1301 radio spectrometer, the 57Fe M6ssbauer spectra were recorded on a YAGRS-4 spectrometer with a 57Co ,,/-ray source in chromium with the signals recorded in a NTA-1024 multichannel analyzer, followed by least-squares analysis of the two doublets on a IBM PC/AT computer. The 27AI and 31p spectra were recorded on a Brucker (Germany) SKHR-90 pulsed Fourier spectrometer, using a "solid-echo" sequence in the high-power regime with external stabilization of the magnetic field. The chemical shifts in the 3tp NMR spectra were read from the signal from an 85 % solution of H3PO 4 used as an external standard. EPR Spectra of Fe 3+ Ions. Figure 1 displays the EPR spectrum of Fe 3 + ions in SAP glass, containing 6 mass % Fe203. For [Fe203] < 4 mass% the EPR spectrum consists of two lines with g-factors of 4.3 and 2, which are determined by the isolated Fe 3+ ions occupying, respectively, tetra-(FeO4) and octahedral positions (FeO6) in the glass structure [1]. The third (wider) line in the region g = 2 (dashed line in Fig. 1) is manifested in the spectrum only with Fe203 content in the glass exceeding 4 mass%. This line was identified with clusters of iron ions, which are characterized by ferromagnetic properties. Figure 2 displays the intensity (Iv_) of the EPR spectrum as a function of the iron oxide concentration in SAP glass with the following composition (mass%): 25 Na20-21AI203-53P xOs-xFe203 (x = 0.4-6 mass%). In the region [FexO 3] <4% In is a linear function of [Fe203]. At high iron oxide concentration the linear relation breaks down because of the sharp increase in the intensity of the line corresponding to iron-ion clusters, which eliminate the direct proportionality between the iron concentration in the clusters and the intensity of the EPR spectrum.

Effects of composition on selected physical properties of SiO2-K2O-Na2O glasses

Physical properties were used to characterize a range of five, three-component glass formulations (SiO2-K2O-Na2O) synthesized from spray-dried precursor powders in terms of their final bulk chemical compositions. Five specimens per composition were produced by mixing dry glass powder with methyl alcohol to form a slurry, then shaping the slurry in a cylindrical mould, using conventional methods. Specimens were fired under vacuum. Optimum firing conditions for each glass were determined by selecting holding times which produced the maximum Young's modulus. Fracture toughness,K IC, values ranged from 0.92–0.99 MPa m1/2 and Young's modulus,E, values ranged from 45.09–58.06 GPa. Linear regression analyses showed significant correlations between chemical composition and fusion temperature (n=5;P<0.001), opacity (n=5;P <0.01), specific gravity (n=5;P<0.02), dynamic Young's modulus (n=5;P<0.01) and fracture toughness (n=30;P<0.001). The selected physical properties were found to be very sensitive to small variations in chemical composition.

Ionic conductivity in a network of silicate glasses: Extension of a previous model to three-component glasses

In this paper we describe the ionic conductivity in silicate glasses by using equations which include non-linear behaviour as a function of ionic concentration. We analyzed binary-alkali silicate glasses, PbOSiO 2 and three-component glasses, namely Na 2OROSiO 2 (R = Mg, Zn, Ca, Pb, Sr, Ba). The alkali concentration varied in the molar concentration 15–35%, while in the case of three-component glasses the ratio between RO and Na 2O concentrations ranged from 0.1 to 3.1. Taking into account that the analyzed experimental results refer to a wide temperature (300 K < T < 900 K) and concentration ranges, the obtained theoretical agreement is satisfactory.

Wide-band multimode graded fiber waveguides

Multimode graded fiber waveguides were formed from a three-component glass (Ge, P):SiO2 with the dispersion optimized simultaneously at two wavelengths of 0.85 and 1.3 µ. Optimization of the parameters of the MCVD process and their correction on the basis of the results of measurements of differential mode delays in fiber waveguides increased the average bandwidth-duration product up to 0.9 GHzkm at the wavelength of 0.85 µ and up to 1 GHzkm at 1.3 µ.

Preparation and Mechanical Properties of Mg‐Al‐Si‐O‐N Glasses

A three‐component glass system (Mg–Al–Si) was nitrided by adding amorphous and crystalline Si3N4. Glasses with varying amounts of nitrogen were melted, and their mechanical properties were measured. Density, hardness, Young's elastic modulus, and fracture toughness increased with increasing nitrogen content.

Sintering and properties of zircon ceramic with glass-forming additives

The sintering and properties of a ceramic based on zircon with additions corresponding to eutectic mixtures of three-component glasses have been studied.

Internal Friction of Simple Alkali Silicate Glasses Containing Alkaline‐Earth Oxides: II, Interpretation and Discussion

The results of internal friction measurements on simple three‐component glasses that were reported in Part I of this paper are discussed. From a consideration of the basic equations governing internal friction and examination of the results of other investigators, a basis of interpretation is developed. It is shown that changes in peak‐temperature position can be explained by changes in the activation energy of the process causing the peak. A change in peak height not accompanied by a change in the shape of the peak is shown to be due to a change in the concentration of the relaxation mechanisms. Using this information the changes in the peaks due to composition variations are explained on a structural basis. A mechanism is also suggested to explain the new high‐temperature peak. A critical examination of the measurements on alkali‐free and phosphate glasses leads to the conclusion that it may be necessary to re‐evaluate some of the concepts concerning the low‐temperature peak in alkali silicate glasses.

Transmission of near-infrared energy by some two- and three-component glasses

Transmission of near-infrared energy by some two- and three-component glasses

A Three-component Glass Filter to Correct the Spectral Sensitivity Curves of Selenium Rectifier Photoelectric Cells to that of the Eye for Photopic Vision

The preparation of a filter to correct the spectral sensitivity curve of a selenium photoelectric cell to that of the eye for photopic vision is described and the spectral sensitivity curves for three makes of British cell are given. The filter consists of a light yellow, a dark yellow and a blue-green glass cemented together with Canada balsam. The glass types and the correction obtained are described.