Synthesis of a new class of high-entropy nitride ceramics and the effects of nitrogen vacancies on their magnetic properties

Authors：Zhao, Lei; Sun, Xiaoyan; Zeng, Xianghui^*; Li, Yang; Fang, Wei; Du, Xing; He, Xuan; Wang, Daheng; Li, Weixin; Chen, Hui^*

Source：Applied Surface Science, 2023, 618: 156543.

DOI：10.1016/j.apsusc.2023.156543

• High-entropy nitride
• Ammonia nitridation
• Nitrogen vacancy
• Magnetic properties

This research prepared a new type of (Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)N0.956 high-entropy nitride (HEN) ceramic powder with a cubic single-phase zinc blende structure using the (Co,Cr,Fe,Mn,Ni)3O4 high-entropy spinel oxide as raw material through ammonia nitridation. Nitrogen vacancies are the main feature of HENs, considerably influencing the HEN their structure and magnetic properties. (Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)N0.864 HENs with ni-trogen vacancies were synthesized through hydrogenation. Theoretical calculations and experimental charac-terization results show that the samples obtained by heat treatment at 300 degrees C for 30 min in Ar/H2 atmosphere have the most nitrogen vacancies. Nitrogen vacancies affect the interactions among metal ions in the crystal, resulting in the spin tilt of some divalent metal ions requiring more energy; thus, coercivity (Hc) decreases from 411.98 to 251.40 Oe, and saturation magnetization (Ms) increases from 5.71 to 8.09 emu/g. We offer a fresh viewpoint to explain the structural origin of magnetic characteristics in high-entropy ceramics based on the theoretical calculations of the association between defects, structure, and magnetism as well as the character-ization data.