Fluoroaluminate glasses

The 4Ii3/2 - 4Iis/2 infrared emission band of Er3+ ions in fluorozirconate glass is displayed in Fig. 11. The band maximum is located at 1.53 /an and the width at half-maximum is as broad as 60 nm, which favors the use of this transition for optical amplification in the third telecommunication window. In bulk geometry, 1.6 jtm CW-laser action is reported for a Cr, Yb, Er-codoped fluoroaluminate glass slab pumped by a krypton laser [114],... 

In the last few years, only a few studies have been devoted to the optical properties of Sm3+ ions in fluoride glasses [138,139], The main result concerns the excitation of the 4G5/2 level by a three-fold up-conversion process including a direct two-photon absorption mechanism. Izumitani et al. have succeeded in stabilizing divalent samarium in fluoroaluminate and fluorohafnate glasses [140], Absorption spectra reveal a strong 4f - 5d transition whose maximum is located around 320 nm. Emission of Sm2+ ions in fluoroaluminate glass occurs in the red, between 680 nm and 810 nm, from the 5D0 excited state to the 7Fj (J = 0, 1, 2, 3, 4) levels. 

The knowledge of the structures of HMFG is still very incomplete, being in fact limited to a few fluoroaluminate glasses and to several FZ systems. However, even in the latter case, a great deal of controversy is still apparent. 

Izumitani, X, X Yamashita, M. Tokida, K.. Miura and H. Tajima, 1987, Physical, chemical properties and crystallization tendency of the new fluoroaluminate glasses, in Halide Glasses for Infrared Fiberoptics, ed. R.M. Almeida (Martinus Nijhotf, Dordrecht) pp. 187-196. Jacoboni, C, B. Boulard and P. Baniel, 1987, Mater. Sci. Forum 19-20, 253.. 

Many other systems have subsequently been found to display anion conductivity. The electrical conductivity of lead fluoroborate and fluorogermanate glasses is similar to that of the lead fluorosilicate glasses. Calcium fluoroaluminate glasses also conduct by fluorine migration. Fluorophosphate glasses have also proven to be good anionic conductors. All of these systems are free of alkali ions. 

Heumann E, Ledig M, Ehrt D, Seeber W, Duczynski EW, Vanderheide HI et al (1988) CW laser action of Er " in double sensitized fluoroaluminate glass at room-temperature. Appl Phys Lett 52 255-256... 

All fluoride glasses have excellent optical properties and transmit more than 50% between 0.25 pm and 7pm. While fluoroaluminate glasses do not transmit as far as fluorozirconate glasses, non-ZrF4 based on heavy metal can transmit to even longer wavelengths. As a result, fluoride glasses are candidate materials for both bulk windows and fibers for the IR. 

M. Body, C. Legein, G. Silly, J.-Y. Buzare, F high speed MAS NMR investigation of AIFe " octahedron connectivity in fluoroaluminate glasses, J. Non-Cryst. Solids, 353, 2231-2236 (2007). 

Figure 10.18 Photograph of a sample of the fluoroaluminate glass 37AIF3-12BaF2-15CaF2-12MgF2-9SrF2-15Yp3 (molar %) that has undergone thermomechanical analysis (TMA) indentation viscometry with a cylindrical probe. The sample has devitrified during the indentation [35].

Molten salts or ionic liquids (also referred to as fused salts by some authors) were among the very first media to be employed for electrochemistry. In fact, Sir Humphrey Davy describes electrochemical experiments with molten caustic potash (KOH) and caustic soda (NaOH) [1] as early as 1802 A wide variety of single molten salts and molten salt mixtures have been used as solvents for electroanalytical chemistry. These melts run the gamut from those that are liquid well below room temperature to those melting at more than 2000°C. The former present relatively few experimental challenges, whereas the latter can present enormous difficulties. For example, commercially available Teflon- and Kel-F-shrouded disk electrodes and Pyrex glass cells may be perfectly adequate for electrochemical measurements in ambient temperature melts such as the room-temperature chloroaluminates, but completely inadequate for use with molten sodium fluoroaluminate or cryolite (mp = 1010°C), which is the primary solvent used in the Hall-Heroult process for aluminum electrowinning. 

Nd3+ ions are by far the most widely investigated ions in all types of materials, essentially because of the ideal, 4-level, 1.06 m laser transition from 4F3/2 to 4In/2 shown in Fig. 5. Thus, the spectroscopic properties of Nd3+ ions are reported for a large number of different compositions of fluorozirconate, fluoroindate, fluorohafnate, fluoroaluminate and other kinds of fluoride glasses [31,36,63-69]. 

In alkali fluoroaluminate solid compounds, aluminum is present only in octahedral coordination with fluorine. According to Spearing et al. (1994) and Smith and Van Eck (1999), their Al chemical shifts range between -13 and -1.4 ppm and are typically more shielded than the AlOe octahedrons in oxide compounds. Only a few studies report lower coordination numbers for Al in fluorides. Kohn et al. (1991) have described the Al MAS NMR spectra of glasses of jadeite mixed with cryolite in terms of the 5-fold and 6-fold coordination of aluminum at 22 and -5 ppm, respectively. Herron et al. (1993) reported a Al chemical shift at 49 ppm for the tetrahedral anion AIFJ in a [l,8-bis-(dimethylamino) naphtathalene H ] [AIFJ] saturated solution. 

Alcan Recovered Cryolite. [Alcan] Sodium fluoroaluminate (87-90%), aluminum oxide (2%), sodium sulfate (4%), sodium carbonate (1-1.5%) source of fluorine as ceramic flux and opacifler aid in the prod, of vitreous enamels, glass, glazes, abrasives metallurgical flux in refining of aluminum and its alloys. 

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