Abstract Crystal structure design and the relevant morphology design are two main methods to get a quality microwave absorber. To figure out the effective mechanism of these two factors on microwave absorption, MnO2 was chosen due to the characteristic of multiphase and multimorphology. In this paper, four independence samples have been successfully obtained, combining with the dipole calculation, the efforts of phases (α and δ) and morphologies (nanowires and microspheres) of MnO2 on microwave absorption performance have been full-scale discussed. Due to the larger dipole moment and higher conductivity, the α-MnO2 perform better dielectric loss than δ-MnO2; nanowires with more interfaces and trapping centers is the optimal structure for the absorbers compared with microspheres. As a result, nanowires-α-MnO2 (NA) shows the best absorption performance, reflection loss value of NA-wax composite can reach −39.6 dB at 2.64 GHz with 6 mm thickness, and effective absorbing can be achieved in the band of 2.4–18 GHz by selecting the proper thickness of absorber. This work not only provides the design concept of MnO2 as microwave absorbing materials, but also exhibits the insight that to get an excellent absorber is to synthesize the proper kind of materials and optimize the microstructure.

中文翻译：

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从两个维度洞察MnO2的电磁吸收性能：晶体结构和形貌设计

摘要 晶体结构设计和相关形貌设计是获得优质微波吸收体的两种主要方法。为了弄清楚这两个因素对微波吸收的有效机制，由于多相和多形貌的特性，选择了MnO2。本文成功获得了四个独立的样品，结合偶极子计算，全面讨论了MnO2的相（α和δ）和形貌（纳米线和微球）对微波吸收性能的影响。由于更大的偶极矩和更高的电导率，α-MnO2的介电损耗比δ-MnO2要好；与微球相比，具有更多界面和俘获中心的纳米线是吸收体的最佳结构。因此，nanowires-α-MnO2 (NA) 显示出最好的吸收性能，NA-wax 复合材料的反射损耗值在 2.64 GHz 时可以达到 -39.6 dB，厚度为 6 mm，并且可以在 2.4-18 GHz 频段实现有效吸收选择合适的吸收体厚度。这项工作不仅提供了 MnO2 作为微波吸收材料的设计概念，而且展示了获得优秀吸收体是合成合适的材料和优化微观结构的见解。