Influence of Zr4+-Co2+ substitution on structure, morphology and dielectric properties of BaZn2U-type hexaferrites

Abstract

A series of Zr4+-Co2+ substituted U-type hexaferrites (Ba4Zn2Fe36-2xZrxCoxO60 (0.0 ≤ x ≤ 1.0, having Δx = 0.25)) were synthesized via sol-gel auto-combustion method. The samples were sintered at 1200 ° C for 6 h. The impact of Zr–Co substitution on phase, structure, morphology, and dielectric behavior were investigated through XRD, FTIR, SEM, XPS and VNA. XRD studies shows that the U-type hexaferrite phase has been developed and the increase in lattice constants (a & c), cell volume, c/a ratio, and percentage porosity was observed. Sample with x = 0.25 exhibited the smallest crystallite size (34.5 nm). The existence of signature metal-oxygen vibrational bands for hexaferrites was observed by FTIR spectra. SEM analysis reflects that the substitution produces a significant effect on morphology and grain size of the samples. X-ray photoelectron spectra (XPS) of sample x = 1.0 confirmed the chemical and elemental composition. The dielectric constant, dielectric loss, and ac conductivity increases with increasing frequency and decreases with Zr–Co substitution. The lowest reflection loss of RL = −64.5 dB (with MW absorption >99.9 %) was observed for the composition x = 0.5 with pellet thickness of 1.73 mm at 1.05 GHz frequency. Due to the improved bandwidth and better absorption, these hexaferrites can be used in microwave and high frequency applications.