Determining the Actual Composition of Nb<sup>5+</sup>–Ni<sup>2+</sup> Codoped Barium Ferrites to Controllably Regulate the Microwave Absorbing Properties
Chuyang Liu, Zhiwei Chen, Xueyu Xiang, Gang Fang, Zongrong Wang, Yujing Zhang, Piyi Du
Abstract
The substitution amount of foreign ions for Fe3+ ions significantly influences the electromagnetic and microwave absorption performance of barium ferrite. To establish the correlation between composition and property, Nb5+–Ni2+ codoped M-type barium ferrite powders with molar ratio of the added Ba2+, Fe3+, Nb5+, and Ni2+ ions being 1:(12–2x):x:x (x = 0–0.8) were prepared by the sol–gel method. The actual substitution amount of Nb5+ and Ni2+ ions for Fe3+ ions are theoretically determined based on the measured concentrations of Fe2+ ions, surface absorbed oxygen, and the lattice parameters of the doped barium ferrite. The calculation results demonstrate that the substitution amount of Ni2+ ions is obviously lower than that of Nb5+ ions in the doped barium ferrites, while the total substitution amount of Nb5+–Ni2+ is still higher than the only Nb5+ ions doping case. As a result, the multiresonant permeability is obviously achieved and dual reflection loss peaks with broad bandwidth ∼12 GHz are apparently observed in the BFNNO with x = 0.4–0.6 over 18–40 GHz. Moreover, the frequency of reflection loss peaks can be adjusted to cover wider frequency range −18 GHz to +40 GHz with variation of x from 0 to 0.8. The developed theoretical calculation approach provides powerful guidance for the controllable design of material composition and regulation of microwave absorption.