Fig. 2a and b shows the XRD patterns of the precursor of manganese
oxalate and Mn2O3 nanobundles. In Fig. 2a, all the reflections
in the pattern could be indexed on the basis of an
monoclinic cell reported for manganese oxalate dihydrate (JCPDS
No. 25–0544, a = 12.016 Å, b = 5.632 Å, c = 9.961 Å), indicating the
pure manganese oxalate dihydrate precursor was obtained. All of
the reflections of the XRD pattern in Fig. 2b can be indexed to
the standard pattern of the pure cubic phase of a-Mn2O3 which
is in good agreement with the reported data (JCPDS No. 78–
0390). This revealed that the Mn2O3 sample produced a singlephase
cubic structure. From XRD data, the crystallite size (Dc) of
as-prepared Mn2O3 particles was calculated to be 21 nm using
the Debey–Scherrer equation [32],