The transport properties of the mixed Ni-Cu ferrite

The transport properties of mixed Ni-Cu ferrite are measured as ac electrical conductivity and thermoelectric power with a function of temperature and frequency. The results obtained for these materials reveal a semiconductor-metallic-semiconductor behavior as Cu content increase. All studied compositions exhibit a transition with the conductivity versus temperature. This transition temperature is found to decrease with increasing Cu content. The dielectric parameter (ɛ′) and loss (tan δ) are measured for all the compositions Ni1−xCuxFe2O4 with x = 0.0, 0.2, 0.5, 0.8, and 1.0 as a function of temperature at frequency range 200-100 kHz. The conduction mechanism is discussed on the basis of the hopping model. The thermoelectric power φ is positive at room temperature for most samples, and the values of φ tend towards negative values, indicating n-type behavior at high temperature.