Development of Cu2+ substituted Ni–Zn ferrite nano-particles and their high-temperature semiconductor behaviour

Cu substituted nickel-zinc ferrites with composition Ni_0.2Cu_xZn_0.8-xFe₂O₄ (x ?= ?0 to 0.8) were developed with the technique of citrate-gel method. Rietveld analysis confirmed Fd-3m space grouped cubic spinel structure of single phase. Dislocation density (?) and packing factor percentage (%) of samples under study increase with increased Cu composition. The fine and uniform structure was confirmed from the studies of morphology index. Measurements on electrical resistivity were taken up by using the two-probe method at high temperatures. Arrhenius plots confirm an increase in observed resistivity (Ω) of ferrite samples with a temperature increase. The energy of activation in the ferromagnetic region (E_F) is less when compared to that of the paramagnetic region (E_P). The hopping mechanism decreases Curie temperature, while the activation energy of hopping increases with an increase in Cu substitution. Mobility of charge carriers and temperature are inversely correlated.