Ti4+ and Ge4+ ionic substitution in Cu-ferrite,electrical conductivity and thermoelectric power

Both the DC conductivity and the thermoelectric power of Cu_1+xGe_xFe_2−2xO₄ and Cu_1+xTi_xFe_2−2xO₄ ferrites, for 0⩽x⩽0.4, were measured in a wide range of temperature from RT up to 773 K. The measurements showed that the substitution of both tetravalent ions (Ge⁴⁺ and Ti⁴⁺) tend to convert Cu-ferrite from n- to p-type semiconductor. The results were analyzed on the basis of the small polaron model. The cation distribution for each system was proposed. The activation energy ΔE, Fermi energy E_F, the density of charge carriers n or p and the carriers mobility μ were determined for both systems. In addition, an energy band schemes of Cu–Ge and Cu–Ti ferrites were schematically represented.