Phosphorus Vacancy-Induced Built-In Electric Field for Electromagnetic Properties Modulation.

Anion vacancy engineering represents an effective strategy to construct built-in electric fields (BIEFs) for the purpose of modulating electromagnetic (EM) properties. However, the in-depth and systematic comparative analysis of the effects of various anionic vacancies on defect-induced polarization is still lacking. In this work, the effects of defect-induced polarization resulting from group VA anion vacancies, particularly phosphorus vacancies (V_P), are compared to the anion vacancies of other elements. The EM property modulation mechanisms and quantitative structure-property relations of NiCo_0.5Fe_0.5P_1-x with varying contents of V_P are investigated. It is concluded that the high content of V_P establishes more intense BIEFs, forming permanent induced dipoles that function as polarization centers, thus enhancing defect-induced polarization and improving permittivity and dielectric loss. NiCo_0.5Fe_0.5P_1-x3 with a high content of V_P exhibits significant reflection loss (RL) with multi-band compatibility and wide effective absorption bandwidth (EAB) covering the whole X-band. This work offers a constructive perspective on the exploration of anionic vacancies from group VA, particularly V_P, in modulating EM properties. Additionally, it addresses the issue of incompatibility associated with multi-band strong microwave absorption (MA) and offers a viable strategy for designing advanced metal phosphide MA materials.