Tuning of electromagnetic properties in Ba(MnZn)xCo2(1-x)Fe16O27/NBR flexible composites for wide band microwave absorption in 6–18 GHz

Abstract

W-type barium cobalt hexaferrites substituted with different concentrations of Mn2+, Zn2+ ions in Ba(MnZn)xCo2(1-x) F16O27 (x = 0.0, 0.3, 0.4, 0.5 and 0.7) have been prepared by simple and cost effective solid state process. From XRD analysis, the systematic incorporation of these ions into lattice of ferrite has been confirmed from gradual decrease in lattice parameters of its hexagonal structure. SEM analysis reveals the formation of distorted hexagonal platy morphology of these powders with particles size of 2–15 µm with thickness of 1–2 µm for x = 0.4. With an appropriate substitution of Mn2+, Zn2+ (x = 0.4), ferrite showed the highest saturation magnetization (Ms) and broad magnetic loss tangent (tan δm) > 0.8 over 6–18 GHz with maximum value ~ 1.4 at 15 GHz. To obtain flexible microwave absorber, Ba(MnZn)0.4Co1.2F16O27/NBR composites have been prepared with different loading percentage (50–80 wt%) of ferrite for investigation of microwave absorption properties. Composite with higher content of ferrite (NBR-F80) shows >90% microwave absorption (RL > 10 dB) over 7.5–14 GHz with maximum value of ~ –37 dB at 10.5 GHz at absorber thickness of ~ 2.5 mm. The maximum absorption and bandwidth (RL > 10 dB) of absorber can be tuned with variation of thickness from 2.0 to 3.0 mm within 6–18 GHz. The maximum absorption of the absorber is attributed to the presence of large content of ferrite and its hexagonal plate like morphology of particles, which enhances multiple scattering within material. The fabricated flexible rubber based MW absorbers may be a potential candidates for wide band frequency applications on any target with complex geometry.