Defect Induced Polarization Loss in Multi‐Shelled Spinel Hollow Spheres for Electromagnetic Wave Absorption Application

Abstract

Defect engineering is an effective approach to manipulate electromagnetic (EM) parameters and enhance absorption ability, but defect induced dielectric loss dominant mechanism has not been completely clarified. Here the defect induced dielectric loss dominant mechanism in virtue of multi-shelled spinel hollow sphere for the first time is demonstrated. The unique but identical morphology design as well as suitable composition modulation for serial spinels can exclude the disturbance of EM wave dissipation from dipolar/interfacial polarization and conduction loss. In temperature-regulated defect in NiCo 2 O 4 serial materials, two kinds of defects, defect in spinel structure and oxygen vacancy are detected. Defect in spinel structure played more profound role on determining materials' EM wave dissipation than that of oxygen vacancy. When evaluated serial Co-based materials as absorbers, defect induced polarization loss is responsible for the superior absorption performance of NiCo 2 O 4 -based material due to its more defect sites in spinel structure. It is discovered that electron spin resonance test may be adopted as a novel approach to directly probe EM wave absorption capacities of materials. This work not only provides a strategy to prepare lightweight, efficient EM wave absorber but also illustrates the importance of defect engineering on regulation of materials' dielectric loss capacity.

Lightweight Ni Foam‐Based Ultra‐Broadband Electromagnetic Wave Absorber

“…The differences in work function of materials are reported to cause the redistribution and accumulation of charges in interfaces thus leading to interfacial polarization. [26,[66][67][68][69] The work function of Ni, ZnO, NiO, and NiFe 2 O 4 are 5.1, 5.3, 5.4, and 4.61 eV, respectively. [70][71][72][73] In Zn5, the interfacial polarization comes from Ni/ZnO (5.1 eV/5.3 eV) interface.…”

Influence of Mg substitution on structural, magnetic and electrical properties of Zn-Cu ferrites

“…Hard ferrites, which are difficult to magnetize due to their high coercivity, are used to produce permanent magnets that have been used for applications in the loudspeaker, refrigerator, communication system, washing machine, TV, switchmode power supply, dc-dc converter, microwave absorption system, etc. [4,[7][8][9]. On the other side, soft ferrites behave as good conductors at low magnetic field due to their low coercivity, whose magnetization can be easily altered.…”

Architecting functionalized carbon microtube/carrollite nanocomposite demonstrating significant microwave characteristics

“…It is found that CuCo 2 S 4 nanoparticles and FCMT/CuCo 2 S 4 nanocomposite showed the considerable imaginary part of permeability, derived from the intrinsic features of nanoparticles. These phenomena are realized by the produced crystal defects, distortions, and dislocations, as well as the induced magnetic dipole moments, established by the unique interactions at grain boundaries 104 , 105 . Eddy current loss plays a vital role in microwave absorption.…”