Microstructure and defect investigations of the layered manganites La2-2xCa1+2xMn2O7 (x=0.6, 0.8 and 0.9) by HREM

The microstructure and defects of the n=2 Ruddlesden-Popper manganites La2-2xCa1+2xMn2O7 (x=0.6, 0.8 and 0.9) were investigated by electron diffraction and high-resolution transmission electron microscopy. Besides the predominant n = 2 layered structure in the examined compounds, intergrowths with different number of the perovskite-like layers were observed. Intergrowth of n = 1 (K2NiF4-type) was ob-served only in x = 0.9 sample. Intergrowths with n >= 5, essential perovskite microdomains or inclusions, were seen in the x = 0.8 and 0.6 samples. The type of defects in x = 0.8 sample is much richer than that in x = 0.6 and 0.9 samples and two rare types were observed and analyzed. Some of edge dislocations in the x = 0.6 specimen were presented. (C) 2009 WILEY-NCH Verlag GmbH & Co. KGaA, Weinheim