Solvothermal treatment of rare earth chloride hydrates

The reaction of rare earth (RE) chloride hydrates in 1,4-butanediol (1,4-BG) at 300 degrees C in the presence of small amounts of n-hexylamine and 1,6-hexanediamine yielded phase-pure RE(OH)(2)Cl for La-Dy, but RE(OH)(2)Cl obtained from Ho to Yb and Y was contaminated with an unknown compound. The space group of RE(OH)(2)Cl formed by this reaction was P2(1)/m [No. 11]. Thermal analysis of the products in an air flow indicated that the RE(OH)(2)Cl phases for the RE elements other than Cc were dehydrated into REOCl, while Ce(OH)(2)Cl was decomposed at 350 degrees C yielding CeO2 without formation of CeOCl. For the RE elements with smaller ionic size, REOCl was further decomposed into RE2O3 but REOCl with larger ionic size was not decomposed even after calcination at 1000 degrees C. The morphology of RECl3 was altered by the solvothermal reaction, indicating that RE(OH)(2)Cl were formed via a dissolution-crystallization mechanism. (c) 2005 Elsevier B.V. All rights reserved.