Molecular and Ionic Species in Vapor over Molten Ytterbium Bromides

Molecular and Ionic Species in Vapor over Molten Ytterbium Bromides 

Butman, D. N. Sergeev, V. B. Motalov, L. S. Kudin, L. Rycerz and M. Gaune-Escard  

Lanthanide atoms are known to most likely exist in halogen compounds in a stable trivalent state. The thermodynamics of vaporization of LnX3 was recently studied fairly completely [1-4], Europium, ytterbium, and samarium are exceptions for which reliable thermodynamic characteristics of the vaporization process have virtually not been published. This primarily accounts for the incongruent character of evaporation [5,6] and the valence transformation Ln(III) Ln(II) in these compounds at high temperatures, which is in accord with the general tendency toward decreasing stability of the trivalent state in the lanthanide series [7, 8] La, Lu, Gd, Ce, Tb, Pr, Er, Nd, Ho, Pm, Dy, Tm, Sm, Yb, and Eu. Their thermal decomposition occurs due to the decreased stability of the state of Ln(III) in tribalogenide compounds [1]  

On the other hand, it was noted in [7] that lanthanide dihalogenides disproportionate at high temperature via the reaction  

Unfortunately, no detailed information on the conditions of the reaction in Equation 3.7.2 has been published, with the exception of data for LnCl2 compounds, which disproportionate under vacuum at T 1273 K [9, 10]. The type of reaction in Equation 3.7.2 was determined mainly by analyzing the composition of the condensed phase, whereas the composition of the gas phase during this reaction was not investigated. 

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