Raman spectroscopic studies of the thermal decomposition mechanism of ammonium metavanadate

Thermal decomposition of NH4VO3 under N-2 and NH3 + H2O has been studied on a molecular level by in situ Raman spectroscopy in the temperature range 150-400 degrees C. Under N-2, the decomposition mechanism leading to formation of V2O5 has been observed to proceed via two intermediates: viz. an amorphous, transitional (NH4)(2)V4O11 and NH4V3O8. Under NH3 + H2O, a slightly different decomposition pathway, rationalized in terms of stability of intermediates, leading to the formation of V2O3 has been observed. The identification of Raman-inactive V2O3 is further supported by the formation of V2O4 and V2O5, along with monomeric vanadyl species, through oxidation of V2O3 at 400 degrees C.