K2NiF4-type (Ca2-xSmx)MnO4 (0.02 <= x <= 03) 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 Mn-O(2)-Mn angle, and the (Ca,Sm)-(Ca,Sm) distance. The samples were n-type semiconductors, and the minimum values of electrical resistivity (rho) and an energy gap (E-g) at x=0.1 were accounted by electron transfer through an Mn-O(2) -Mn path and overlap between the Mnt(2g) and Op(pi) orbitals. In the sample (x= 0.3), the log rho-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 315-325K. (C) 2015 Elsevier Ltd. All rights reserved.