Crucial role of percolation transition on the formation and electromagnetic properties of BaTiO 3 /Ni 0.5 Zn 0.47 Fe 2 O 4 ceramic composites

BaTiO3/Ni0.5Zn0.47Fe2O4 ceramic composites with various compositions were sintered at different temperatures. It is found both the formation and electromagnetic properties of the composite ceramics are strongly dependent on the percolation transition of NZFO. As NZFO content x is low (x=0.1 and 0.2), the density increases with increasing the sintering temperature T from 1220°C to 1300°C, while it decreases as x is high (x=0.65, 0.75 and 0.85). It is ascribed to the mismatch between the densification of BTO and NZFO. Both the permeability and low-frequency permittivity of the composites exhibit typical percolation behaviors, which are appropriate to the Kirkpatrick׳s effective medium model with the percolation threshold fc ranging from 0.35 to 0.5. As xfc, both the permeability and permittivity increase considerably with increasing T. By analyzing the magnetic and dielectric dispersion spectra, it is revealed they are attributed respectively to the enhancement of domain-wall motion and the increase in the grain conductivity of NZFO.