On the Formation of Cerium Molybdates under different atmospheric and thermal conditions

Abstract

The thermal degradation products of Ce2(MoO4)3 · 4.5 H2O were studied by means of thermogravimetric analysis, x‐ray diffraction and spectroscopical methods under rigorously controlled conditions. From the crystalline hydrate various amorphous and crystalline products with a Ce/Mo ratio 2/3 may be obtained by variation of the thermal and atmospheric conditions. In nitrogen, the decomposition pattern leads directly to Ce2(MoO4)3 with a pseudo‐scheelite structure, in air or oxygen atmosphere oxidation takes place below 450°C, resulting in amorphous or crystalline ceric molybdate, γ‐Ce2Mo3O13. About above 500°C both in inert and oxidizing conditions oxygen desorption leads to Ce2(MoO4)3. Reoxidation of this compound to Ce2Mo3O12,25 is possible at higher temperatures, giving also CeO2 by oxidative degradation. The thermal stability of γ‐CeMo3O13 differs from other such substances with the same stoichiometric composition.

Mechanisms of Localized Corrosion Inhibition of AA2024 by Cerium Molybdate Nanowires

“…The XRD pattern corresponding to the initial cerium molybdate nanowires indicates that these nanomaterials are amorphous, without any defined crystalline phase. However, the nanowires revealed structural changes after immersion in NaCl solutions, with a phase consisting of Ce 2 (MoO 4 ) 3 •4.5H 2 O, 44 formed after immersion in 0.05 M NaCl. Apparently, the NaCl solution induces reorganization of the amorphous phase into a more stable and crystalline form.…”

Investigation of CeO2, MoO3, and Ce2(MoO4)3, Synthesized by the Pechini Method, as Catalysts for Fructose Conversion

“…the thermogram obtained for CeMo (Table 2 and Figure S1, Supplementary Materials), only one thermal decomposition event was observed above 1000 °C (with a mass loss of 19%), which clearly continues to occur, but which is not quantified due to the limitation of the equipment, which operates at a maximum temperature of 1500 °C. This suggests that the interaction between the molybdenum and cerium ions for the formation of cerium molybdate leads to an increase in thermal stability, and the mass loss above 850 °C is associated with the decomposition of the material into cerium and molybdenum oxide and the subsequent sublimation of MoO3 [47][48][49]. Reports indicate that in this type of material, when subjected to temperatures above 700 °C, defects are formed that favor greater mobility of the molybdenum and cerium ions, consequently leading to changes in the mutual interaction between them, leading to increased thermal stability [48].…”