Maxwell–Wagner polarization in grain boundary segregated NiCuZn ferrite

• We find the existence of CuO-rich grain boundary segregation in NiCuZn ferrite after the sintering process.
• Phase segregation makes the present ferrite electrically heterogeneous giving rise to dielectric relaxation process.
• The relaxation principally originates from heterogeneity and has Maxwell–Wagner origin.

The present work investigates the polarization response in polycrystalline Ni0.9−yCuyZn0.1Fe1.98O4−δ (y = 0, 0.1, 0.2, 0.3, 0.4, 0.5) ferrite synthesized by solid–state reaction method. X-ray diffraction analysis confirmed cubic spinel phase formation in the calcined samples. Sintered samples contain a continuous network of CuO-rich segregation along the grain boundaries for y ≥ 0.2. Dielectric spectra showed a relaxation peak for y ≥ 0.2 in the frequency range of 1 kHz–1 MHz. This relaxation has been explained based on Maxwell–Wagner polarization considering two-layer model in connection with two heterogeneous dielectric media.