Low-loss Z-type barium hexaferrite composites from nanoscale ZnAl2O4 addition for high-frequency applications

In this study, nanocrystalline ZnAl2O4 (ZA) were introduced to Z-type barium hexaferrite (Co2Z) and the effects of ZA addition upon the crystal-phase composition, microstructure, permeability and permittivity as well as losses characteristics over a wide frequency range of 10 MHz–1 GHz have been systematically investigated. With increasing ZA content (x) from 0 to 15 wt%, the permeability μ′ at low frequencies decreased from 12.0 to 4.3, while the permittivity ε′ was decreased from 27.4 to 10.7. Correspondingly, the frequency stability of permeability and permittivity were improved and the losses were effectively reduced. When x is in the range of 5–10 wt%, the magnetic loss tan δμ is in the order of 10-2 and the dielectric loss tan δε is in the order of 10-3 at 300 MHz, which is lower by one order of magnitude compared with that of undoped Co2Z. The modified magnetic and dielectric properties are closely related to the changing phase composition and microstructure.