Nitrogen Transfer between Solid Phases in the System Mn‐N Detected via in situ Neutron Diffraction. Issue 23 (2nd October 2017)

• Record Type: Journal Article
• Authors: Widenmeyer, Marc; Hansen, Thomas C.; Leineweber, Andreas; Weidenkaff, Anke; Niewa, Rainer
• Is Part Of: Zeitschrift für anorganische und allgemeine Chemie. Volume 643:Issue 23(2017)
• Page Start: 1929
• Page End: 1938
• Publication Date: 2017-10-02
• Subjects: Manganese -- Nitrides -- in situ -- Neutron diffraction -- X‐ray diffraction; Chemistry, Inorganic -- Periodicals; Chemistry -- Periodicals; 540
• DOI: 10.1002/zaac.201700304
• Languages: English
• ISSNs: 0044-2313

Abstract

Abstract : The thermochemical properties of θ‐Mn6 N5+ x and ζ‐Mn2 N1– w were investigated by thermal analysis in inert and oxidizing atmospheres. The obtained phase transformation temperatures were used to design an in situ neutron diffraction experiment on the reaction of α‐Mn and flowing NH3 . During this in situ experiment, initially a nitrogen‐poor anti‐perovskite type phase ε‐Mn4 N y [0.70(3) ≤ y ≤ 0.93(3)] was formed, indicating the lowest required nitridation potential necessary for formation of this phase within the binary manganese nitrides. At slightly higher temperatures the γ‐ and β‐type superstructured polymorphs of ζ‐Mn2 N1– w were observed. In the same temperature region the formation of η‐Mn3 N2 [up to 26(2) wt %] at ambient pressure conditions was noticed. For the first time, a direct evidence for the high‐temperature transformation of η‐Mn3 N2 was obtained. At 928 K the nuclear and magnetic superstructures simultaneously collapse and a cubic MnN x phase [0.56(6) ≤ x ≤ 0.70(3)] with defect rock salt structure was generated. Clear indications for the preferred transfer of N between the different above mentioned solid state nitride phases rather than direct release to the surrounding atmosphere during temperature increase were achieved from the compositions of the coexisting phases. An updated phase diagram is suggested. Abstract :