Studies of Mn valence conversion and oxygen vacancies in La1-xCaxMnO3-y using electron energy-loss spectroscopy

Using the white line intensities, electron energy-loss spectroscopy in a transmission electron microscope has been employed to characterize the valence conversion and oxygen vacancies in La1-xCaxMnO3-gamma. For a nominal doping composition x=0.33, the ratio of Mn4+ to Mn3+ is determined to be more than 0.25 but less than 0.5, and the content of oxygen vacancy gamma is no more than 0.065 (equivalent to 2.2 at. % of the oxygen content). At gamma(max)=0.065, 60% of the residual charge introduced by Ca doping is balanced by the conversion of Mn3+ tp to Mn4+ and 40% by oxygen vacancy. (C) 1997 American Institute of Physics.