Influence Of Jahn–Teller (Cu2+) Ions Substitution On Charge Carrier Mobility And Seebeck Coefficient Of Nickel Ferrites

Polycrystalline ferrite samples of Ni₁₋ₓCuₓFe₂O₄ (x = 0.0, 0.2, and 0.6) were synthesized using the standard double-sintering ceramic technique to investigate the effect of Cu²⁺ ion substitution on the charge carrier mobility and Seebeck coefficient. X-ray diffraction confirmed mono-phase cubic spinel structures for all compositions. The electrical conductivity and thermoelectric power were measured in the temperature range 300–950 K. The results reveal that conductivity increases with Cu content due to enhanced Fe²⁺/Fe³⁺ hopping and reduced activation energy. The Seebeck coefficient is negative, indicating n-type semiconducting behavior dominated by electron conduction. Its value decrease up to certain temperature and then start increasing, consistent with small-polaron hopping conduction. The enhanced carrier mobility and tunable thermoelectric properties make Cu-doped nickel ferrites potential candidates for spintronic and thermoelectric applications.