Abstract: Polarization loss is a kind of dielectric loss, which has equal importance as conductivity loss, but often has not attracted enough attention from researchers. How to precisely regulate the EMW absorption performance by adjusting the polarization loss is now scarce but urgently needed. Herein, an anion-doped-induced vacancy engineering strategy is developed to promote polarization loss and thus enhance electromagnetic wave (EMW) absorption property. The S vacancy can be introduced in two different ways (hydrothermal and calcination) and it turns out that more S vacancies can be harvested by the calcination method. Moreover, it’s worth noting that the co-doping of Se and S can further promote vacancy formation and thus enhance the vacancy level. As a result, the fabricated c-CoNi₂S_4-xSe_x-rGO aerogel manifests distinguished EMW absorption performances with a strong reflection loss (RL) of -40.3 dB and a broad effective absorption bandwidth (EAB) of 7.04 GHz at the thickness of 2.5 mm with a low filling content of 5 %. Such superior EMW absorption performance is attributed to the large number of vacancies formed by the co-doping of S and Se atoms, resulting in abundant dipolar polarization loss. In addition, the polarization loss and conduction loss of the materials are quantitatively analyzed and discussed, and the relationship between the vacancy level and the polarization loss is determined. This work not only demonstrates the importance of polarization loss but also illustrates the correlation between vacancies level and polarization loss, providing a vital guiding significance for accurately regulating the EMW absorption properties of materials.

Key words: Electromagnetic wave absorption, Polarization loss, c-CoNi₂S_4-xSe_x-rGO aerogel, Anion-doped-induced, Vacancy engineering