Impact of Chromium Substitution on Structural, Spectroscopic, and Dielectric Properties of Ba4Ni2Fe36O60 Ceramics

Abstract

Cr-substituted Ni₂U hexaferrite series (Ba₄Ni₂Fe_36-xCr_xO₆₀for x = 0.0 to x = 2.0 with a step size of 0.5) was prepared via sol-gel auto-combustion route and annealed at 1200 ˚C for 6hours. The samples were investigated using XRD, FTIR, SEM, XPS, and high frequency (1MHz to 6 GHz) dielectric and microwave absorption measurements (VNA). XRD studies revealed that Cr³⁺ ions successfully substituted in BaNi₂U-type hexaferrite and have a single-phase structure. The average crystallite size decreased while the percentage of porosity increased with the substitution. FTIR spectra confirmed the formation of the hexaferrite phase in all compositions. SEM micrographs revealed that the prepared samples are hexagonal. XPS spectra show the presence of all constituent elements in the samples. The dielectric constant, dielectric loss, and A.C. conductivity of samples was analyzed. Cole-Cole plots with single semicircles of different radii show the grain and grain boundaries affecting the conduction process. Moreover, Cr-substitution enhanced the microwave absorption capability. The hexaferrite sample Ba₄Ni₂Fe₃₅ Cr_1.0O₆₀, with a pellet thickness of 1.81mm, showed the highest M.W. absorption at 1.09 GHz frequency with a reflection loss (R.L.) value of -55 dB. The hexagonal-shaped morphology, high porosity, and enhanced reflection loss value suggest their use in high-frequency microwave applications.