Kinetic Study of Europium Oxide Chlorination
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UCTION
THE group of elements having the atomic number (Z) 57 to 71 is usually classified as lanthanides and very often referred to as rare earths, europium (Eu) being one of them with the atomic number 63.[1] It is well know that rare earth elements play an important role in many fields of advanced materials science and that their demand tends to increase from year to year.[2] Europium is utilized primarily for its unique luminescent behavior. Excitation of the europium atom by absorption of ultraviolet radiation can result in specific energy level transitions within the atom creating an emission of visible radiation.[3–5] In energy-efficient fluorescent lighting, europium provides not only the necessary red but also the blue. They have exhibited great potentials in applications such as laser materials,[6] organic electroluminescent materials,[7] chemical sensors,[8] and analytical or structure probes.[9]
FEDERICO J. POMIRO, Researcher, is with the Complejo Tecnolo´gico Pilcaniyeu, Departamento de Fisicoqui´mica y Control de Calidad, Centro Ato´mico Bariloche, Comisio´n Nacional de Energi´a Ato´mica. Av. Bustillo 9500, 8400 Bariloche, Ri´o Negro, Argentina. Contact e-mail: [email protected] GASTO´N G. FOUGA, Researcher, is with the Complejo Tecnolo´gico Pilcaniyeu, Departamento de Fisicoqui´mica y Control de Calidad, Centro Ato´mico Bariloche, Comisio´n Nacional de Energi´a Ato´mica, also with Consejo Nacional de Investigaciones Cienti´ficas y Te´cnicas (CONICET), Buenos Aires, Argentina. ANA E. BOHE´, Researcher, is with the Complejo Tecnolo´gico Pilcaniyeu, Departamento de Fisicoqui´mica y Control de Calidad, Centro Ato´mico Bariloche, Comisio´n Nacional de Energi´a Ato´mica, also with Consejo Nacional de Investigaciones Cienti´ficas y Te´cnicas (CONICET), and also with Centro Regional Universitario Bariloche, Universidad Nacional del Comahue, 8400 Bariloche, Ri´o Negro, Argentina. Manuscript submitted February 25, 2013. METALLURGICAL AND MATERIALS TRANSACTIONS B
High temperature chlorination and carbochlorination of ores using gaseous chlorination agents have been widely investigated for metal extraction processes, including rare earths’ extraction. The resulting rare earth chlorides are important for the extraction of rare earth metals due to the development of various rare earth intermetallic materials.[10–12] Extraction of the rare earths by chlorination requires relatively high temperatures and long reaction times. In addition, the rare earth chlorides have a very similar volatility, so that mutual separation is not expected in the sublimation processes. However, rare earth chlorides with lower volatility can react with the aluminum chlorides or alkaline chlorides, forming the vapor complexes such as LnAlnCl3n+3[13] or ALnCl4[14] (Ln = rare earth elements, A = alkaline elements, n = 1 to 4). The mutual separation and recovery of rare earths, called chemical vapor transport reaction (CVT), was studied intensively. The separation of rare earth elements was investigated from binary and ternary oxides mixtures, su
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