The crystal structure and electrical properties of K2NiF4-type (Ca2−xSmx)MnO4

K2NiF4-type (Ca2−xSmx)MnO4 (0.02 ≤ x ≤ 0.3) was synthesized using a polymerized complex route. The crystal structure changed from tetragonal to orthorhombic at x = 0.3. A variation in the lattice parameters was explained by the Mn–O(2) distance, the MnO(2)Mn angle, and the (Ca,Sm)–(Ca,Sm) distance. The samples were n-type semiconductors, and the minimum values of electrical resistivity (ρ) and an energy gap (Eg) at x = 0.1 were accounted by electron transfer through an MnO(2)Mn path and overlap between the Mnt2g and Opπ orbitals. In the sample (x = 0.3), the log ρ–1000/T curve consisted of two different lines that intersected at ca. 325 K, and a peak was observed at ca. 315 K in the magnetic susceptibility–temperature curve. These results indicated the presence of a charge-ordering (CO) transition at 315–325 K.