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Abstract: A systematic study has been carried out for the stepwise chlorination-chemical vapor transport (SC-CVT) characteristics of pure rare earth oxides from Sc2O3 to Lu2O3 mediated by the vapor complexes KLnCl4 and NaLnCl4 (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 KCl as complex former, the main deposition temperature of the rare earth chlorides LnCl3 is in the increasing order ScCl3 ScCl3, 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 EuCl3 and GdCl3 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 LaCl3, CeCl3, YbCl3 and LuCl3, while the total transport amount of rare earth chloride for KCl as complex former is higher than that for NaCl except for LaCl3 and EuCl3. 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 AlCl3 as complex former. [Copyright &y& Elsevier]

Abstract: Mutual separation characteristics for ternary oxide mixtures Y2O3–Ho2O3–Er2O3, in which these three kinds of rare earth ion (III) have very similar ion radius values, have been investigated using a stepwise chlorination-chemical vapor transport (SC-CVT) reaction mediated by vapor complexes KLnCl4 in different temperature gradients. Both the main deposition temperature region tendency and total transport amounts of chlorides for YCl3 with respect to the ion radius of Y (III) were exceptional compared with those of LnCl3 (Ln=Ho and Er), which were observed both in the degressive temperature gradient and the wave type temperature gradient. All the three chlorides produced from the oxide mixtures concentrated in the middle temperature range from 1150 to 1000K (FN=5–9) in degressive temperature gradient. The deposition temperature of the largest chlorides amounts was at FN=6 for YCl3 and FN=8 for HoCl3 and ErCl3, which in the order of YCl3 >HoCl3 ≈ErCl3. Total transported yields of the chlorides was in the order of HoCl3 >ErCl3 >YCl3 in the two type temperature gradients. The largest separation factors 7.48 for Ho:Y, 5.10 for Er:Y and 7.58 for Ho:Er in the lower temperature region were observed in the degressive temperature gradient, respectively. Furthermore, the improved separation factor values of 23.8 for Ho:Y and 19.2 for Er:Y were obtained in the wave type temperature gradient due to variation of the dynamic conditions of CVT. The results were discussed on the difference between the ionic structure of Y and 4f lanthanoid elements of Ho and Er and verified that the ionic radius of the rare earth is one of the decisive factors of CVT reaction only for lanthanoid elements, not for Y. On the other hand, the cooperate effect among the three elements and the variation of the dynamic conditions of CVT have been the important factors to influence the separation efficiency of the three elements. [Copyright &y& Elsevier]

Abstract: Mutual separation characteristics for a series of rare earth elements Sc, Y, La, Nd, Sm, Gd, Ho and Er from their binary oxide mixtures Er2O3–Sc2O3, Er2O3–Y2O3, Er2O3–La2O3, Er2O3–Nd2O3, Er2O3–Sm2O3, Er2O3–Gd2O3 and Er2O3–Ho2O3 has been investigated using a stepwise chlorination-chemical vapor transport (SC-CVT) reaction mediated by vapor complexes KLnCl4. The total transported yield of the chlorides produced from the oxide mixtures was in the order of ErCl3 >ScCl3, ErCl3 >YCl3, ErCl3 >LaCl3, ErCl3 >NdCl3, ErCl3 >SmCl3, ErCl3 >GdCl3 and HoCl3 >ErCl3, and the total separation factors are 13.0 for Er:Sc, 1.49 for Er:Y, 1.48 for Er:La, 1.15 for Er:Nd, 2.33 for Er:Sm, 2.72 for Er:Gd and 1.10 for Ho:Er. The largest separation factors 1213.8 for Er:Sc, 6.37 for Er:Y, 189.3 for Er:La, 100.6 for Er:Nd, 105.7 for Er:Sm, 27.8 for Er:Gd and 1.14 for Er:Ho in the lower temperature region, while 102.7 for La:Er, only 14.3 for Nd:Er, 16.7 for Sm:Er, 4.0 for Gd:Er and 2.04 for Ho:Er in the higher temperature region were observed, respectively. The results showed the obvious divergence effect of Gd both in the largest separation factors, the total separation factors and total transport efficiency. Furthermore, the results were discussed on the difference of ionic radius of Sc and Y on the one side and the lanthanoid elements of La, Nd, Sm, Gd, Ho and Er on the other hand, and verified that the ionic radius is one of the decisive factors only for lanthanide elements, not for Sc and Y. [Copyright &y& Elsevier]

Abstract: Mutual separation characteristics for binary oxide mixtures Y2O3–Dy2O3, Y2O3–Er2O3 and Ho2O3–Er2O3, in which these four kinds of rare earth ion(III) have very similar ion radius values, using a stepwise chlorination–chemical vapor transport (SC–CVT) reaction mediated by vapor complexes KLnCl4 have been investigated in different temperature gradients. The unexpected results, together with that for Y2O3–Ho2O3 reported previously, are used to make a comparative analysis for the effect of ion radius values on the SC–CVT reaction for mutual separation of rare earths. Both the main deposition temperature region tendency and total transport amounts of chlorides for YCl3 with respect to the ion radius of Y(III) were exceptional compared with those of LnCl3 (Ln=Dy, Ho and Er), which were observed both in the degressive temperature gradient and the wave-type temperature gradient. The main deposition temperature of the chlorides produced from the oxide mixtures was in the order of DyCl3>YCl3, HoCl3ErCl3, total transported yields of the chlorides was in the order of DyCl3>YCl3, HoCl3>YCl3, ErCl3>YCl3 and HoCl3>ErCl3, and the largest separation factors 11.49 for Dy:Y, 15.28 for Ho:Y, 6.37 for Er:Y and 2.04 for Ho:Er in the lower temperature region were observed in the degressive temperature gradient, respectively. The results were discussed on the difference of ionic structure of Y on the one side and 4f lanthanoid elements of Dy, Ho and Er on the other hand, and verified that the ionic radius of the rare earth is one of the decisive factors of CVT reaction only for lanthanoid elements, not for Y. Furthermore, the improved separation factor values of 4.22 for Ho:Er and 3.20 for Er:Ho were obtained in the wave type temperature gradient due to variation of the dynamic conditions of CVT. [Copyright &y& Elsevier]

Mutual separation characteristics for binary oxide mixtures Ho2O3–Sc2O3, Ho2O3–Y2O3, Ho2O3–La2O3, Ho2O3–Nd2O3 and Ho2O3–Sm2O3 using a stepwise chlorination-chemical vapor transport (SC-CVT) reaction mediated by vapor complexes KLnCl4 have been investigated. The total transported yields of the chlorides produced from the oxide mixtures was in the order of HoCl3>ScCl3, HoCl3>YCl3, LaCl3>HoCl3, HoCl3>NdCl3 and HoCl3>SmCl3, the main deposition temperature of the chlorides is in the increasing order of ScCl3, and the largest separation factors 19.0 for Sc:Ho, 15.3 for Ho:Y, 125.0 for Ho:La, 10.6 for Ho:Nd and 13.6 for Ho:Sm in the lower temperature region, while 1480.0 for Ho:Sc, only 2.1 for Y:Ho, 50.0 for La:Ho, 15.2 for Nd:Ho and 9.0 for Sm:Ho in the higher temperature region were observed, respectively. The results were discussed on the difference of ionic radius of Sc, Y and La on the one side and 4f lanthanides elements of Ho, Nd and Sm on the other hand, and verified that the ionic radius is one of the decisive factors only for lanthanide elements, not for Sc and Y. Furthermore, the SC-CVT characteristics mediated by vapor complexes KLnCl4 of binary oxides Ho2O3–Ln2O3 were studied compared with that of Y2O3–Ln2O3 mediated by KLnCl4 or LnAlnCl3n+3 for the ionic radius of Ho3+ and Y3+ are very near. [Copyright &y& Elsevier]

Stepwise chlorination–chemical vapor transport (SC–CVT) reaction has been investigated for the rare earth oxide mixtures Gd2O3–Tb4O7, Tb4O7–Dy2O3 and Dy2O3–Ho2O3 mediated by vapor complexes LnAlnCl3n+3 (where Ln=rare earth elements). The results show selective deposition of lighter elements at higher temperatures. The separation factors are 5.84 for Gd/Tb, 3.72 for Tb/Dy and 3.13 for Ho/Dy when using CO as the CVT carrier gas. A combination of enhanced separation factor with reduced total transport yield is also observed for the Tb4O7–Dy2O3 system when using argon as the CVT carrier gas. [Copyright &y& Elsevier]