By using a new furnace design, M(3)AlF(6) (M = Na, K, Cs) and mixtures of small amounts of AlF(3) in FLiNaK (46.5 mol % LiF, 11.5 mol % NaF, 42 mol % KF) and CsF-KF eutectic have been investigated over a wide temperature range (25-1050 degrees C) by Raman spectroscopy. The peak positions and their relative intensities have been measured as a function of temperature. In FLiNaK, up to 750 degrees C, the bands shift gradually to lower wavenumbers, and their halfwidths increase in agreement with published data. However, it is shown from solubility measurements and Raman data that, in these conditions, the mixture is not totally molten and the spectra correspond mainly to AlF(6)(3-) in the solid state. When the mixture is completely molten, a new band appears clearly on the high-frequency side of the main band of the spectrum, and its intensity grows up when the temperature is increased. The present results are a clear confirmation of the dissociation of AlF(6)(3-) into AlF(5)(2-) and AlF(4)(-) that our study of the Raman bands of the fully melted systems MF-AlF(3) (M = Na, K, Li) previously suggested. On these systems, it is then important to know if the spectra belong mainly to solid or liquid fluoroaluminates before drawing any conclusion concerning the liquid phase structure.

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A Dy2O3 single crystal has been used as a seed for the growth of isothermally melt-textured Dy-123 material. The nucleation-controlled step has been observed to be related to the heterogeneous nucleation of 211 particles at the surface of the dysprosium oxide single crystal. The subsequent growth mode seems to be controlled by a high concentration gradient of dysprosium in the liquid phase. This leads to a directional solidification process of the 123 phase. The size of the 211 particles seems to decrease as the distance from the dysprosium oxide single crystal increases.

IR and Raman spectra IR and Raman spectra D 6530The Dissociation of Fluoroaluminates in FLiNaK and CsF-KF Molten Mixtures: A Raman Spectroscopic and Solubility Study. -(AUGUSTE, F.; TKATCHEVA, O.; MEDIAAS, H.; OESTVOLD, T.; GILBERT*, B.; Inorg. Chem. 42 (2003) 20, 6338-6344; Lab. Anal. Chem. Electrochem., Univ. Liege, B-4000 Liege, Belg.; Eng.) -Schramke 48-017