Low temperature fired and electromagnetic properties of a novel ferroelectric/ferromagnetic composite material

A series of Bi4Ti3O12/Ni0.25Cu0.2Zn0.55Fe2O4 ferroelectric–ferromagnetic composites were prepared by the usual ceramic technology and sintered at 900 °C to adapt to the low temperature cofired ceramic (LTCC) technology. Among all samples, the relative density changes in the range of 94.9–96.4% and reaches the highest value in the composite with 30 wt% Bi4Ti3O12 (BIT). When BIT content increases from 0 to 90 wt%, the magnetic and dielectric properties show different change trends: the permeability (real part) at 1 MHz reaches the maximum 170 in the composite with 10 wt% BIT at first, and then gradually decreases from 170 to 1.4, while the saturation magnetization decrease from 2.85 × 105 A/m to 1.6 × 104 A/m; the dielectric loss tangent obtains a maximum value about 0.47 in the composite with 10 wt% BIT at first, and then decreases sharply, while the permittivity (real part) at 1 MHz increases from 8.8 to 100.3. The Maxwell Garnett mixing rule was used to predict the magnetic and dielectric properties of the composites with different assumptions. The calculated results basing on BIT matrix were more approximate to the measured in comparison to that basing on ferrite matrix.

► A novel ferroelectric–ferromagnetic composite material was prepared at 900 °C.
► High density (94.9–96.4%) can be obtained at 900 °C without adding fluxing agents.
► Good electromagnetic properties can be achieved by adjusting Bi4Ti3O12 content.
► Influences of microstructure on sintering and magnetic properties were discussed.
► The effective medium theory was used to predict the electromagnetic properties.