Preparation of (Fe x Ni1− x )4N (0.5 ≤  x  ≤ 0.8) compounds and evaluation of their magnetic and microwave absorbing properties

(FexNi1−x)4N (0.5 ≤ x ≤ 0.8) compounds were prepared by combining a simple reduction route with nitridation process under flowing ammonia gas at various temperatures. The microstructure as well as magnetic and microwave absorbing properties of as-prepared products was investigated. The reflection loss of (FexNi1−x)4N-paraffin composites with a filler mass fraction of 50% was calculated from permittivity and permeability, and the magnetization hysteresis loops of the composites were measured at 300 K. It has been found that the saturation magnetization value of as-prepared products increases as x rises from 0.50 to 0.80. Particularly, the reflection loss of (Fe0.67Ni0.33)4N-paraffin composite (x = 0.67) with a matching thickness of 2 mm is −17.5 dB at 12.0 GHz, lower than that of the composites with x = 0.50, 0.75, and 0.80. Moreover, (Fe0.67Ni0.33)4N-paraffin composite with a matching thickness of 2 mm has the reflection loss exceeding −10 dB in a maximum frequency range of 10.5–14.0 GHz, which is ascribed to its proper match of electromagnetic parameters and large magnetic loss. In one word, (Fe0.67Ni0.33)4N has great potential as a thin broadband microwave absorbent.