TEMPERATURE-DEPENDENCE OF ELECTRICAL-RESISTIVITY AND THERMOELECTRIC-POWER IN CU1+X2+TIX4+FE2-2X3+O42- FERRITES

Electrical resistivity and thermoelectric power measurements are made on the system Cu1+x2+Tix4+Fe2-2x3+O42-with x = 0.05. 0.1, 0.15, 0.2 and 0.3. These compounds are studied in wide range of temperature from 300 to 800 K. Impurity conduction is favoured below 400 K while it is due to hopping of polaron at higher temperatures. The conduction process at low temperature is governed by the reaction Cu(A)+ + Cu(A)2+ --> Cu(A)2+ + Cu(A)+, while at higher temperature it is due to intersite cation exchange and reoxidation such as Cu(A)2+ + Fe(B)3+ --> Cu(B)2+ + Fe(A)3+. Near and above Curie temperature, the conduction process is due to segregation of Cu-rich and Cu-poor domains. The change in sign of alpha supports this conduction process. The sign reversal temperature increases with increase of (Cu-Ti) content.