Thermodynamic Properties of the Rare Earth Element Vapor Complexes LnAl₃Cl₁₂ from Ln = La to Ln = Lu

Abstract

Systematic analysis of rare earth element complexes has been carefully carried out in the liquid and solid states but not in the gaseous state because of the lack of a complete set of experimental data for any kind of vapor complexes of all rare earth elements. Here we present experimental quenching results which suggest that the LnAl(3)Cl(12) complexes are the predominant vapor complexes roughly in the temperature range 588-851 K and pressure range 0.01-0.22 MPa for all of the 14 rare earth elements Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. For these elements, thermodynamic functions of the reactions LnCl(3)(s) + (3)/(2)Al(2)Cl(6)(g) = LnAl(3)Cl(12)(g) were calculated from the measurements. Those for the radioelement Pm were smoothly interpolated. The results show Gd divergences from the standard enthalpies and standard entropies from LaAl(3)Cl(12) to LuAl(3)Cl(12).

Comparative study for mutual separation characteristics of binary mixed oxides Y2O3–Ln2O3 (Ln=Dy, Ho and Er) and Ho2O3–Er2O3 using stepwise chlorination–chemical vapor transport reaction mediated by vapor complexes KLnCl4

“…Indeed, this idea was verified by Adachi et al [11] and Wang et al [25,26] from different point of view very recently. Wang et al's investigation has established that Sc, Y and lanthanoid elements have different complex compositions: LnAl 3 Cl 12 is the dominant complexes species for the whole series of lanthanoid elements from Ln = La to Lu [25] while LnAl 2 Cl 9 for Ln = Sc and Y [26] in the same temperature and pressure range.…”

“…Wang et al's investigation has established that Sc, Y and lanthanoid elements have different complex compositions: LnAl 3 Cl 12 is the dominant complexes species for the whole series of lanthanoid elements from Ln = La to Lu [25] while LnAl 2 Cl 9 for Ln = Sc and Y [26] in the same temperature and pressure range. Adachi et al [11] obtained the lowest transport efficiency of YCl 3 and the abnormal separation characteristics of YCl 3 with LnCl 3 (Ln = Dy, Ho and Er) by CVT process mediated by LnAl n Cl 3n+3 or KLnCl 4 and discussed on the basis of their very similar ionic radius and the difference in the ionic structure and electronic configuration of Y(III) with those of Ln(III).…”

Stepwise chlorination-chemical vapor transport reaction for rare earth separation from ternary oxide mixtures Y2O3–Ho2O3–Er2O3 mediated by vapor complexes KLnCl4

“…Indeed, very recently, this idea was verified by Adachi et al [11] and Wang's group [26,27] from different point of view. Wang's groups' investigation has established that Sc, Y and lanthanoid elements have different complex composition: LnAl 3 Cl 12 is the dominant complexes species for the whole series of lanthanoid elements from Ln = La to Lu [26] while LnAl 2 Cl 9 for Ln = Sc and Y [27] in the same temperature and pressure range.…”

“…Wang's groups' investigation has established that Sc, Y and lanthanoid elements have different complex composition: LnAl 3 Cl 12 is the dominant complexes species for the whole series of lanthanoid elements from Ln = La to Lu [26] while LnAl 2 Cl 9 for Ln = Sc and Y [27] in the same temperature and pressure range. Adachi's group [11] obtained the lowest transport efficiency of YCl 3 and the abnormal separation characteristics of YCl 3 with LnCl 3 (Ln = Dy, Ho and Er) by CVT process mediated by LnAl n Cl 3n+3 or KLnCl 4 and discussed on the basis of their very similar ionic radius and the difference in the ionic structure and electronic configuration of Y (III) with those of Ln (III).…”

Mutual separation characteristics for binary mixed oxides Ho2O3–Ln2O3 (Ln = Sc, Y, La, Nd, Sm) using stepwise chlorination-chemical vapor transport reaction mediated by vapor complexes KLnCl4

“…Recently, Wang et al [22][23][24][25] have determined the thermodynamic properties of the gaseous species LnAl n Cl 3n+3 for all of rare earth elements including Sc and Y, and found that LnAl 3 Cl 12 is the predominant gaseous complex species for the lanthanide series from La to Lu while LnAl 2 Cl 9 for Sc and Y in the temperature range from 500 to 900 K. On the other hand, Adachi and co-workers [13,14] have reported the CVT characteristics of the binary oxide mixtures Sc 2 O 3 -Y 2 O 3 [13], Sc 2 O 3 -La 2 O 3 [13] and Y 2 O 3 -Ln 2 O 3 (Ln = La [13], Dy [14], Ho [14] and Er [14]) mediated by gaseous complexes LnAl n Cl 3n+3 and KLnCl 4 . The experiment results [13,14] indicated that ScCl 3 could be easily separated from YCl 3 and LaCl 3 while the separation efficiency between Y and Ln (Ln = Dy, Ho and Er) is very small and unexpected results that the lowest CVT efficiency and that the lowest gaseous complexes stability for YCl 3 compared with LnCl 3 (Ln = Dy, Ho and Er) were observed.…”