Systematics and Anomalies in Rare Earth/Aluminum Bromide Vapor Complexes: Thermodynamic Properties of the Vapor Complexes LnAl3Br12 from Ln = Sc to Ln = Lu

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• 作者：Zhi-Chang Wang ; Jin Yu
• 刊名：Inorganic Chemistry
• 出版年：2007
• 出版时间：May 14, 2007
• 年：2007
• 卷：46
• 期：10
• 页码：4248 - 4255
• 全文大小：121K
• 年卷期：v.46,no.10(May 14, 2007)
• ISSN：1520-510X

文摘

Systematics and anomalies in the rare earth/aluminum bromide vapor complexes have been investigated by thephase equilibrium-quenching experiments. The measurements suggest that the LnAl₃Br₁₂ complexes are thepredominant vapor complexes for the 16 rare earth elements Ln = Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho,Er, Tm, Yb, and Lu in the temperature range 601-833 K and pressure range 0.01-0.22 MPa, which is differentfrom the rare earth/aluminum chloride systems, where the predominant vapor complexes are LnAl₃Cl₁₂ from Ln =La to Ln = Lu, but LnAl₂Cl₉ for Ln = Sc and Y are roughly in the same ranges, which indicates the importanceof the halogen anion radius on the rare earth vapor complex formation. In the temperature and pressure ranges,gaseous Al₂Br₆ and AlBr₃ are dominant species and the molar fraction of LnAl₃Br₁₂ is normally less than 0.01.Thermodynamic functions of the reactions LnBr₃(s) + (3/2)Al₂Br₆(g) = LnAl₃Br₁₂(g) were calculated from themeasurements for the 16 rare earth elements and then smoothly interpolated for the radioelement Ln = Pm. Thestandard molar enthalpies and standard molar entropies show significant Gd divergences from LaAl₃Br₁₂ to LuAl₃Br₁₂ when plotted as functions of the rare earth atomic number. They also suggest nearly linear manner for ScAl₃Br₁₂, LuAl₃Br₁₂, YAl₃Br₁₂, and LaAl₃Br₁₂ when plotted as functions of the rare earth ionic radius.