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

Abstract

Multi-field susceptible ceramic composite with an ultra high percolation threshold (f_c) and extraordinary performance is of great interest and significance for the design of multifunctional devices. In this work, the percolative BaTiO₃ (BTO)/Ni_0.5Zn_0.5Fe₂O₄ (NZFO) ceramic composite with f_c 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-f_c bi-phased composites that cannot spontaneously form an enwrapped microstructure.