Effect of GeIon on Electrical Properties of (La0.1Ca0.9)(Mn1−xGex)O3

Orthorhombic perovskite-type (La_0.1Ca_0.9)(Mn_1−xGe_x)O₃was synthesized in the range (0.00≤x≤0.10). Since the ionic radius of the Ge⁴⁺ion is equal to that of the Mn⁴⁺ion, the (Mn, Ge)–O(1, 2) distances and the angles for (Mn, Ge)–O(1, 2)–(Mn, Ge) are independent of the composition (x). From the measurement of the electrical resistivity (ρ), all manganates exhibit a metal–insulator transition. With increasingx, the metal–insulator transition temperature (T_t) increases anddρ/dTdecreases. The cation–anion–cation overlap integrals are weakened by the Ge⁴⁺ion.