Enhanced microwave absorption of La0.7Sr0.3MnO3−δ based composites with added carbon black

Composites consisting of carbon black (CB) particles, La0.7Sr0.3MnO3−δ (LSMO) powder, and epoxy resin were prepared for development of a high performance microwave absorber. This study investigated the influence of adding amounts of LSMO powder (60, 70, and 80wt%) on complex permittivity, complex permeability, and reflection loss for CB (5wt%)-epoxy composites. The variation of complex permittivity and complex permeability with frequency of the composites was measured by the cavity perturbation technique in the range of 7–14GHz. It was found that the real part of the complex permittivity increased with increasing LSMO addition and the imaginary part of the complex permeability decreased with increasing frequency. The microwave absorption results indicated that the composite filled with 5wt% CB particles and 80wt% LSMO powder had the best absorption performance. The maximum reflection loss was −23.63dB at 7.87GHz and the absorbing bandwidth at −10dB was 1.75GHz with a matching thickness of 5mm.