Influence of varying particle sizes on microwave absorbing properties of U-type hexaferrites and development of broadband microwave absorber

The present study investigates the influence of particle size variation on the microwave (MW) absorbing properties of (Ba0.7Bi0.3)4Co2Fe34.8Zn1.2O60 U-type hexaferrites. The hexaferrite powders of varying particle sizes were prepared through heating at a constant optimized temperature for different holding time (4, 6, 8 and 10 h) using a novel “one-pot” chemical route. With an increase of the holding time (4 to 10 h), the average particle size is found to increase monotonically (∼65 to ∼170 nm). The hexaferrite sample prepared at a holding time of 8 h exhibits an excellent reflection loss (RL) of ‒44.2 dB (99.99% MW absorption) at 11.6 GHz frequency. In addition, a broadband MW absorber has been developed through an ingenious blending of equal amounts of all four hexaferrite powders. The mixed U-type hexaferrite displays an excellent bandwidth of ∼8.4 GHz for 90% or more MW absorption. The reflection losses (S11) are also measured experimentally through one port short-circuited transmission line method using vector network analyzer (VNA). The strong and broadband absorption results suggest that the prepared U-type samples can be utilized in the high-performance MW absorbing applications.