Multi-field susceptible high-fc ceramic composite with atypical topological microstructure and extraordinary electromagnetic properties

Multi-field susceptible ceramic composite with an ultra high percolation threshold (fc) and extraordinary performance is of great interest and significance for the design of multifunctional devices. In this work, the percolative BaTiO3 (BTO)/Ni0.5Zn0.5Fe2O4 (NZFO) ceramic composite with fc above 0.9 and extraordinary dielectric and magnetic properties was successfully synthesized by a critical-sintering-rapid-cooling-and-post-annealing (CSRC-PA) method. XRD, SEM and EDS were used to analyze the phase structure and observe the morphology of the composite. The analyses reveals that a small amount of crystalline BTO phase enwraps a large amount of bigger-sized crystalline NZFO phase completely and tightly, successfully elevating the percolation threshold above 0.9 (volume fraction of ferrite ∼92%). A precision impedance analyzer and vibrating sample magnetometer were used to measure the dielectric and magnetic properties of the composite. The effective permittivity exceeds 40 000, which is extraordinarily high with a minimum loss tangent of only ∼0.3. The initial permeability and saturation magnetization of the composite, which are ∼106 and ∼76 emu g−1, respectively, approach quite closely to the values of single-phased NZFO ferrite. The composite may be a potential candidate in promoting the miniaturization and integration of modern multifunctional devices, while the CSRC-PA method, based on fundamental chemical principles, is applicable in preparing high-fc bi-phased composites that cannot spontaneously form an enwrapped microstructure.