Electromagnetic wave absorbing properties of Ni-Zn ferrite powder–epoxy composites in GHz range

Abstract Spinel ferrites NixZn1-xFe2O4 (x = 0.4, 0.5, 0.6) with grain sizes ranging from tens of nanometers to several hundred nanometers were prepared using the sol-gel and post-annealing processes. X-ray diffraction (XRD) analysis confirmed that a crystalline single spinel phase could be formed after annealing the sol-gel processed powders at ≥ 400 °C. Reflection loss (RL) maps as functions of frequency (100 MHz ≤ f ≤ 15 GHz) and sample thickness were plotted for the Ni-Zn ferrite–epoxy (10 wt%) composites. The RL patterns were systematically modulated by the Ni-Zn ferrite grain size and Ni composition x. The electromagnetic wave absorbing area of RL