Thermodynamic properties of the rare earth element vapor complexes LnAl(3)Cl(12) from Ln=La to Ln=Lu

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) + 3/2Al(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 LaAl3Cl12 to LuAl3Cl12.