A systemic study of stepwise chlorination-chemical vapor transport characteristics of pure rare earth oxides from Sc_2O_3 to Lu_2O_3 mediated by alkaline chlorides as complex former

摘要

A systematic study has been carried out for the stepwise chlorination-chemical vapor transport (SC-CVT) characteristics of pure rare earth oxides from Sc_2O_3 to Lu_2O_3 mediated by the vapor complexes KLnCl_4 and NaLnCl_4 (Ln = Sc, Y and La-Lu) used NaCl and KCl as complex former, respectively. The results showed that the SC-CVT characteristics are similarly for NaCl and KC1 as complex former, the main deposition temperature of the rare earth chlorides LnCl_3 is in the increasing order ScCl_3 < YCl_3 < LaCl_3, and then with a systematically decreasing trend from the early lanthanide chlorides to the end one. The results also showed that the total transported amount of the produced chlorides is YCl_3 > ScCl_3, and they are much higher than that of most lanthanoid chlorides. For lanthanoids, the total transported amount of chloride increases systematically from the early lanthanoid chlorides to the end one except for EuCl_3 and GdCl_3 mediated by KCl and NaCl as complex former, respectively, which showed the divergence effect of Gd in the total transport efficiency. But there are some differences in SC-CVT characteristics of pure rare earth oxide mediated by KCl and NaCl as complex former, that is the main deposition temperature region for the same rare earth element was lower for KCl than that for NaCl as complex former except for LaCl_3, CeCl_3, YbCl_3 and LuCl_3, while the total transport amount of rare earth chloride for KCl as complex former is higher than that for NaCl except for LaCl_3 and EuCl_3. More over, the discussion was carried out for Sc and Y on the one hand and the lanthanides contain 4f electron as another hand based on the 4f electron hybridization assumption. Further more, the transport characteristics of rare earth oxides with alkaline chlorides as complex former in this study were compared to that with AlCl_3 as complex former.