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 Ni 1− x Cu x Fe 2O 4 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.