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

Both the DC conductivity and the thermoelectric power of Cu1+xGexFe2-2xO4 and Cu1+xTixFe2-2xO4 ferrites, for 0less than or equal toxless than or equal to0.4, were measured in a wide range of temperature from RT up to 773K. 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 DeltaE, Fermi energy E-F, the density of charge carriers n or p and the carriers mobility p were determined for both systems. In addition, an energy band schemes of Cu-Ge and Cu-Ti ferrites were schematically represented. (C) 2002 Elsevier Science B.V. All rights reserved.