Abstract
A three-phase composite with SrTiO3 (STO) ultrafine particles and NiZn ferrite (NZO) ultrafine particles embedded in a polypropylene (PP) matrix was fabricated by using a simple low-temperature hot-pressing technique. The dielectric property and magnetic property of the as-prepared composites were investigated in details, as well as the thermal stability. The results indicate that as the volume of the ceramic fillers is fixed, with the increasing of the ratio of STO phase to NZO phase, the permittivities and dielectric losses of the composites increase while the initial permeabilities and magnetic losses decrease. The cut-off frequencies of the composites are all above 1GHz. Since the low resistivity of NZO, the dielectric losses of the composites are big and decrease with frequency below 100 MHz. Good frequency stability within a wide frequency range has been observed above 100 MHz. For the composite containing 10 vol% STO and 30 vol% NZO, the permittivity, dielectric loss, initial permeability and magnetic loss are 5.7, 0.0025, 2.3 and 0.002 at 100 MHz, respectively. The percolation transition of the composites occurs as the volume fraction of NZO is between 20%-30%. The incorporation of ceramic fillers could improve the thermal stabilities of the composites. Such multifunctional magnetic-dielectric three-phase composites could be used in high-frequency communications for the capacitor-inductor integrating devices such as electromagnetic interference filters.
