Precession electron diffraction of Mn₂O₃ and PbMnO_2.75: solving structures where X-rays fail

The structure solutions of the two phases Mn₂O₃ and PbMnO_2.75 by precession electron diffraction (PED) are presented. In the powder samples used these structures could not be solved by X-ray diffraction because Mn₂O₃ is a minority phase in an MnO₂ powder and the complex structure of PbMnO_2.75 leads to severe peak overlap in the powder diffraction pattern. The influence of different parameters on the structure solution is studied, i.e. the number of reflections measured, precession angle, resolution limit and Lorentz-type correction. It is shown that the number of reflections is the most important parameter for successful structure solution from PED data.