Sm-doped enhanced magnetic-dielectric properties of low-temperature fired Co2Z ferrite materials for high-frequency device applications

Abstract

Co2Z ferrite with superior performance is a beneficial material for high filter devices and antenna substrates. In this work, Ba3Co2Fe24-xSmxO41 (x = 0.00–0.50 with a step of 0.10) materials were prepared using low temperature-fired process with 2.5 wt% of Bi2O3. The phase formation, microstructure, magnetic property, complex permittivity, and complex permeability were studied using X-ray diffraction, scanning electron microscopy, vibrating sample magnetometer, and vector network analyzer. The materials remained in a single hexagonal phase, and the grain size increased with increase of Sm-doped content. Saturation magnetization of samples increased at first and then decreased. When x = 0.20 and 0.30, the value of 4πMS was 2910.4 G and 2861.7 G, respectively. The variation of saturation magnetization is mainly due to the occupancy of Sm3+ ions. When Sm3+ ion doped Fe3+ ion of Co2Z ferrite, Sm3+ ion first preferred to occupy 4eIV site due to its low electronegativity, and then occupied 12k and 4f sites at high doped content, affecting magnetic moment and magneto-crystalline anisotropy. Furthermore, low-temperature sintering improves magnetic-dielectric properties of Sm-doped materials in high-frequency range. The real part of magnetic permeability (μ′) reached a maximum value of 8.4 when x = 0.20 and the real part of dielectric permittivity (ε′) reached a maximum value of 14.1 when x = 0.30. The magnetic loss and dielectric loss remained low (tanδμ = 0.05–0.08 and tanδε = 0.005–0.04) and the off-cut frequency was nearly 1 GHz. The results indicated that these magnetic-dielectric materials have great potential for high-frequency antenna applications.