Single Rare Earth Oxide Chemical Vapor Transport And Fire Laws Of The Mixed Rare Earth Oxide Separation

Rare earth elements have distinct physical chemical properties and play a very important role in the field of advanced materials science and technology. Highly pure rare earths have been used for many advanced materials. But rare earth elements have very similar characteristics and usually coexistent together in minerals. Thus, separation of rare earth has been one of the most difficult problems in rare earth chemistry or in inorganic chemistry.In this study, a new chemical vapor transport (CVT) reaction, so called stepwise selective chlorination-chemical vapor transport (SC-CVT) reaction was designed for investigating the separation characteristics and mechanism of rare earth oxide mixtures. The SC-CVT reaction composed of two steps. One was the selective chlorination of rare earth oxide mixture by Cl2 gas at temperature 800K for 2h.Anothet one was the chemical vapor transport of the resulted rare earth chlorides, the other taking AlCl3 as complex former and Ar gas as carrier gas at T=1300K within 6h.The SC-CVT characteristics was systemically investigated of all the pure rare earth oxides except for the radioactive element Pm .It was observed that the largest deposit region of rare earth oxide had been changed from the higher temperature region to the lower temperature region with the contraction of the lanthanide ionic size of Ln3+ from La to Lu, while the total transported amounts of lanthanide oxide increased with the contraction of the ionic size of Ln³⁺, except for Eu₂O₃, and that both the largest deposit region and the total transport amounts of Sc₂O₃ and Y₂O₃ were not related to the ionic size of Sc3+ and Y3+ .The experimental results provide a new indirect support for Gschneidner's assuming that the electronic orbitals of La3+ in fact contain the 4f composition due to its electron hybridization. The transportation amount using the complex fomer KCl is larger than that of AlCl3.The separation of binary mixed rare earth oxides Y₂O₃-Dy₂O₃,Y₂O₃- Ho₂O₃,Y₂O₃-Er₂O₃ which ionic radium were very closely ,and the neighboring weight rare earth oxides Ho₂O₃-Er₂O₃,Er₂O₃-Tm₂O₃,Tm₂O₃-Yb₂O₃, Yb₂O₃-Lu₂O₃ were investigated by SC-CVT reaction .The results show that the products of reactions of Y₂O₃-Dy₂O₃ ,Y₂O₃- Ho₂O₃,Y₂O₃-Er₂O₃ mostly concentrate in fraction number 9,10,11 .And the separation fractor is high, which is as follows in turn: SFY/Dy=11.49,SFY/Ho=15.28,SFY/Er=6.37; the separation fractor of Ho₂O₃-Er₂O₃, Er₂O₃-Tm₂O₃, Tm₂O₃-Yb₂O₃ , Yb₂O₃-Lu₂O₃ separation.