Thermally induced changes in the oxidation state of cerium(IV) - a study of carbonate and chloro complexes

Madarász, János and Leskela, T. and Pokol, György and Niinisto, L. (1997) Thermally induced changes in the oxidation state of cerium(IV) - a study of carbonate and chloro complexes. JOURNAL OF THERMAL ANALYSIS, 49 (3). pp. 1347-1355. ISSN 0368-4466

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Abstract

Cesium hexachlorocerate(IV), Cs2CeCl6 (I) and sodium pentakis(carbonato)cerate(IV), Na6Ce(CO3)(5).12H(2)O (II) have been investigated in air by simultaneous TG/DTA, FTIR and XRD in order to follow the oxidation state of cerium during their thermal treatment. The thermal decomposition of the hexachloro compound (I) is accompanied by a double change in the oxidation state of cerium. First, in an inner reduction-oxidation reaction, chlorine is evolved and a Cs2CeCl5 phase is obtained. The immediately starting oxidation of this Ce(III) species caused various phase transitions in the CeCl3-CsCl system formed. The presence of Cs3CeCl6 above 400 degrees C can also be assumed and finally this phase also oxidizes into CeO2 with the formation of CsCl as by-product. In the case of the pentacarbonato complex (II), no Ce(III) species were detected. The final products of its decomposition were CeO2 and Na2CO3.

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