Paramagnetic defects in MoO3—revisited

Abstract

Detailed interpretation of EPR signals appearing in commercial MoO₃ upon reduction invacuo at different temperatures is presented. New O^- species in the MoO₃ bulk and Mo⁵⁺ ions without a molybdenyl bond have been found under such conditions, their intensities depending on temperature and time of reduction. It is argued that formation and stabilization of these unusual species is related to traces of nitrogen impurities. A model of redox processes occurring in MoO₃ upon gradual loss of the lattice oxygen and during reconstruction of the MoO₃ lattice upon reoxidation of reduced MoO₃, involving O^- species, as an intermediate stage, is suggested.