Bi3+ doping-adjusted microstructure, magnetic, and dielectric properties of nickel zinc ferrite ceramics for high frequency LTCC antennas

Abstract

Miniaturization, high frequency capability, low loss, and matching impedance play critical roles in new generation antennas. Although ferrite ceramics show a great potential as antenna substrate materials, some challenges still remain associated with their application to high performance antennas. In this work, we synthesized Bi3+-substituted NiCuZn ferrite to adjust the microstructure, magnetic, and dielectric properties at low sintering temperatures. It is shown that Bi3+ substitution not only enhances grain growth and compactness of NiCuZn ferrite at low sintering temperatures, but also effectively tailors the permeability, permittivity, and loss factor. In particular, NiCuZn ferrite doped with 0.025 wt%, of Bi2O3 possesses excellent performance with high permeability (~29.1), high n factor (~22.76), appropriate matching impedance (Z factor = 1.28), and low loss tangents (tanδμ = 0.00853, tanδε = 1.22683 × 10-4). In addition, the dielectric loss is significantly reduced and becomes as low as magnetic loss at high frequencies; the typical tanδε reduces to 1.94 × 10-6, and tanδε/ε´ is greatly decreases to 0.137 × 10-6 at 50 MHz. Thus, Bi3+-adjusted NiCuZn ferrites open up new opportunities for applications in high-frequency LTCC antennas.