Phase Diagrams of Water-rich Parts of the Rare Earth Chloride - Water Systems

Cezary Guminski 

Uniwersytet Warszawski, Wydział Chemii, Warszawa, Poland

Abstract

Rare earth (RE) chlorides are essential compounds used for production of the RE metals, their alloys and compounds, also as catalysts in organic synthesis and polymerization. Because in vicinity of room temperature the RE chlorides crystalize from aqueous solutions as hydrates, it was essential to know the phase relations in this region. The corresponding literature was compiled and critically evaluated what allowed to select the most reliable solubility results (liquidus line) and the equilibrium solid phases of the RE chlorides in water. The selected solubility data do not change much near room temperature whereas at elevated temperatures typical strong bends of the liquiduses are observed reflecting tendencies of the systems to immiscibility. The water-rich parts of the RE chloride - water phase diagrams were constructed for majority of the systems. Shapes of the phase diagrams showed evolutional changes of the invariant points and phase stabilities through the RE series. This fact allowed to predict the phase diagrams of the HoCl3-H2O and TmCl3-H2O systems (which were not investigated) as well as of the PmCl3-H2O system (which due to the high radioactivity cannot be treated experimentally at proper concentrations of PmCl3). Dehydration reactions of the RE chloride hydrates at higher temperatures, decreased pressures and using strong dewaterers are multistage processes, however there are some discrepancies in an uniform description of the reaction stages.

(partly based on achievements of late Tomasz Mioduski)

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Presentation: Poster at E-MRS Fall Meeting 2006, Symposium I, by Cezary Guminski
See On-line Journal of E-MRS Fall Meeting 2006

Submitted: 2006-05-12 13:31
Revised:   2009-06-07 00:44
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