Synthesis of NiLaxFe(2−x)O4 System as Microwave Absorber Materials by Milling Technique

Abstract

The possibility that nickel ferrite doped with lanthanum could be used as a microwave absorbing material has been investigated. Microwave absorbing materials play a very important role in stealth technology, helping military equipment to avoid radar detection. Synthesis of the lanthanum-doped NiFe2O4 ferrite system (NiLaxFe2−xO4) as microwave absorbing materials was carried out. A series of NiLaxFe2−xO4 (x = 0.0025, 0.0050, 0.0075, and 0.01) were prepared using the solid-state reaction method. Each composition was milled using a high-energy milling (HEM) machine then finally sintered at 1000°C for 5 h. Rietveld refinement of x-ray diffraction (XRD) results showed that single-phase nickel ferrite doped with lanthanum in space group Fd-3m was formed for all compositions. The lattice parameter was found to decrease as the doping composition x was increased. Morphological observation by scanning electron microscopy (SEM) revealed that the largest particle size was obtained for the composition with x = 0.0025. Microwave absorption properties obtained by vector network analyzer (VNA) analysis showed that doping with lanthanum enhanced the ability to absorb microwaves from 90.01% to 96.61% (reflection loss −14.72 dB at 10.22 GHz). Thus, the composition with x = 0.01 (NiLa0.01Fe1.99O4) showed an excellent response and can be considered a candidate microwave absorbing material.