By using white line intensities, electron energy-loss spectroscopy in a transmission electron microscope was used to characterize valence conversion and O vacancies in La1-xCaxMnO3-y. When x was equal to 0.33, the Mn4+/Mn3+ ratio was deduced to be between 0.25 and 0.5. The O vacancy content, y, was less than 0.065. This was equivalent to 2.2at% of the oxygen content. When y was equal to 0.065, 60% of the residual charge which was introduced by Ca doping was balanced by the conversion of Mn3+ to Mn4+, and the other 40% was balanced by O vacancies.

Z.L.Wang, J.S.Yin, Y.D.Jiang, J.Zhang: Applied Physics Letters, 1997, 70[25], 3362-4