Harnessing Pseudo‐Jahn−Teller Disordering of Monoclinic Birnessite for Excited Interfacial Polarization and Local Magnetic Domains

Abstract

The symmetry in a polymorph is one of the most important elements for determining the inherent lattice nature. The MnO2 host tends to high‐symmetry MnO6 octahedra as a result of the electronic structure t2g3eg0 of Mn4+ ions, displaying an ordered structure accompanying with poor polarization loss and limiting its application toward high‐performance microwave absorbers. Here, a pseudo‐Jahn−Teller (PJT) distortion and PJT disordering design with abundant self‐forming interfaces and local magnetic domains in the monoclinic birnessite–MnO2 host is first reported. The PJT distortion can give rise to asymmetric MnO6 octahedra, inducing the formation of interfaces and increased electron spin magnetic moment in the lattice. The resultant birnessite with PJT distortions and PJT disordering delivers an outstanding reflection loss value of −42.5 dB at an ultralow thickness of 1.7 mm, mainly derived from the excited interfacial polarization and magnetic loss. This work demonstrates an effective approach in regulating the lattice structure of birnessite for boosting microwave absorption performance.

Intelligent Tunable Wave-Absorbing CNTs/VO2/ANF Composite Aerogels Based on Temperature-Driving

“…However, increasing electromagnetic wave (EMW) pollution and radiation also cause threats to human health and information security. The urgent demand on how to deal with EMW pollution and absorb EMW radiation efficiently has raised great concerns about the development of efficient EMW absorbing materials. − In recent years, many traditional materials such as carbon-based materials (graphene, carbon nanotubes), conductive polymers (ferrites, alloys), and metal-based materials have been applied to electromagnetic wave absorption (EMA) strategies. , Graphene is a two-dimensional structure composed of a single layer of carbon atoms with excellent high electrical conductivity and mechanical strength but is currently expensive to prepare on a large scale and prone to structural changes at high temperatures, affecting performance . Carbon nanotubes have shown great strengths in electromagnetic wave-absorbing materials due to their excellent electrical and thermal conductivity, light weight, and good stability; however, they are easy to agglomerate, are difficult to disperse in the substrate, and have a large dielectric constant, which is not conducive to impedance matching. − The physical properties of aerogels with ultralow density, high porosity, large specific surface area, and low dielectric constant have great potential for modulating EMA. − …”