Transport properties of Ti–Ni spinel ferrites

Polycrystalline ferrites with the composition Ti_xNi_(1+x)Fe_(2−2x)O₄ (0≤x≤0.625) were prepared by a double sintering ceramic method. Results of DC electrical resistivity, ρ_DC, versus a temperature ensured that the samples possess a semiconductive character. Results of Seebeck coefficient S reveal that pure Ni ferrite is n-type semiconductor while the sample with x=0.625 is p-type semiconductor over the whole range of temperature. However, for other samples, S shows a transition from p-type to n-type semiconductor with increasing temperature. On the basis of ρ_DC, S and ρ_AC, the conduction mechanism of Ni–Ti ferrite was determined