Electromagnetic absorbers with Schottky contacts derived from interfacial ligand exchanging metal-organic frameworks

Zhenguo Gao; Yihe Song; Shijie Zhang; Di Lan; Zehao Zhao; Zhijun Wang; Duyang Zang; Guanglei Wu; Hongjing Wu

doi:10.1016/j.jcis.2021.05.009

Electromagnetic absorbers with Schottky contacts derived from interfacial ligand exchanging metal-organic frameworks

J Colloid Interface Sci. 2021 Oct 15:600:288-298. doi: 10.1016/j.jcis.2021.05.009. Epub 2021 May 6.

Authors

Zhenguo Gao¹, Yihe Song¹, Shijie Zhang¹, Di Lan¹, Zehao Zhao¹, Zhijun Wang², Duyang Zang¹, Guanglei Wu³, Hongjing Wu⁴

Affiliations

¹ MOE Key Laboratory of Material Physics and Chemistry under Extraordinary, Northwestern Polytechnical University, Xi'an 710072, China.
² State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China.
³ Institute of Materials for Energy and Environment, State Key Laboratory of Biofibers and Eco-textiles, College of Materials Science and Engineering, Qingdao University, Qingdao 266071, China. Electronic address: wuguanglei@qdu.edu.cn.
⁴ MOE Key Laboratory of Material Physics and Chemistry under Extraordinary, Northwestern Polytechnical University, Xi'an 710072, China. Electronic address: wuhongjing@nwpu.edu.cn.

PMID: 34022725
DOI: 10.1016/j.jcis.2021.05.009

Abstract

Various types of polycrystals have been regarded as excellent electromagnetic (EM) microwave absorbents, while differentiated heterointerfaces among grains usually manipulate conductive loss and polarization relaxation, especially interfacial polarization. Herein, polar facets that dominated the optimization of EM attenuation were clarified by carefully designing polycrystalline Schottky junctions with metal-semiconductor contacts for the first time. An ingenious ligand exchange technique was utilized to construct Zn-MOF (ZIF-L) precursors for Fe-ZnO polycrystals, in which Fe-containing Fe(CN)₆^3- etching ligand acted as metallic source in Schottky junctions. By adjusting the Schottky contacts in polycrystals, the enhanced grain boundaries mainly induced stronger interfacial polarization and affected the microcurrent lightly. This is because Schottky barriers can cause local charge accumulation on heterointerfaces for polarization relaxation. Additionally, the coexistence of Zn and O vacancies brought a lot of lattice defects and distortions for dipole polarization. Thus, optimal EM wave absorbability was obtained by polycrystals with 8 h ligand exchange and an effective absorption band reaching 4.88 GHz. This work can provide guidance for designing advanced polycrystalline EM absorption materials and also highlight the mechanism and requirement of Schottky junctions dominating polarization.

Keywords: Electromagnetic microwave absorption; Interfacial polarization; Polycrystals; Schottky junction.