| Abstract
| - Sr4Mn3O10, which crystallizes in space group Cmca, is not a Ruddlesden−Popper (RP)phase. The partial substitution of either Mn by Fe or Sr by Ca leads to a stable n = 3 RPphase with tetragonal symmetry (I4/mmm). The minimum amount of Fe or Ca needed toobtain a stable RP phase is x = 0.40 for Sr4Mn3-xFexO10-δ and y = 2.85 for Sr4-yCayMn3O10-δ.High-resolution transmission electron microscopy and selected area electron diffractionelectron microscopy indicate that about 50% of the grains have well-ordered n = 3 structurefor both series of RP phases, while the rest of the grains show significant intergrowth betweenthe n = 2 and n = 3 structures. Sr4Mn2.6Fe0.4O10-δ and Sr1.15Ca2.85Mn3O10-δ are semiconductorsand exhibit spin-glass like transitions at low temperature.
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