Grain size effect on the dielectric and magnetic properties of NiFe2O4 ceramics

Nanocrystalline NiFe2O4 powders with different crystal sizes were hydrothermally synthesized with different alkali concentrations at 230 °C. Then the NiFe2O4 nanopowders were sintered at various temperatures to obtain NiFe2O4 ceramics with different grain sizes. The NiFe2O4 ceramic properties were strongly dependent on the grain size. With the increase in the grain size, saturation magnetization (Ms) and magnetic permeability (μ) increased, Curie temperature (Tc) decreased. Dielectric constant enhanced and dielectric loss decreased in nanoferrites. The possible mechanism of grain size dependences was discussed in detail.