Surface activity of antiperovskite manganese nitrides

摘要

Antiperovskite manganese nitrides Mn_3MN (M = Zn, Ni, Cu...) have been extensively studied in the past decade due to their many interesting properties, such as negative thermal expansion. To get a better understanding of the origin of these phenomena, the information from the microscopic scale is necessary, so we performed systematic transmission electron microscopic study of Mn_3Zn_(0.8)Ni_(0.2)N and found that the sample particle is wrapped in a thin MnO layer. The same result was also found in Mn_3Zn_(0.5)Ni_(0.5)N and Mn_3ZnN, indicating that it is a common phenomenon in this kind of compound. The presence of the MnO surface layer was also confirmed by the macroscopic XPS measurements. Our study suggests that M is easier to be lost than Mn in manganese nitrides Mn_3MN (M = Zn, Ni, Cu...), and this character is much more obvious on the surface, i.e., this kind of compound has a strong surface activity. Figure 6 could best represent this manuscript.