Rietveld refinement studies of Nb4N5- and Nb5N6-related phases in the (Mn)-Nb-O-N system
1998 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, Vol. 278, no 1-2, 83-91 p.Article in journal (Refereed) Published
The structures of two Nb and two Mn–Nb (oxy)nitrides have been refined from Cu Kα1 powder diffractometer data by the Rietveld method and have been characterised by electron diffraction. The phases Nb3.49N4.56O0.44 and Mn0.54Nb3.07N4.40O0.60 have structures related to that of Nb4N5, an NaCl type with ordered metal vacancies. Refinements in space group I4/m, with RF=1.3% and 1.1%, respectively, have shown that they are disordered and that metal atoms partially occupy both the nominally filled 8h position and the nominally empty 2a position in the Nb4N5 type. The observed bond lengths indicate that the 2a position is occupied only by Mn atoms in Mn0.54Nb3.07N4.40O0.60. The Nb5N6 type structure of Nb5(N,O)6 and the related structure of MnNb2(N,O)3 has been refined in space group P63/mcm to RF=1.5% and 2.9%, respectively. In the latter, the trigonal prism sites 6g are found to be occupied only by Nb, the octahedral 4d sites by approximately equal amounts Mn and Nb and the octahedral 2a site, empty in the Nb5N6 type structure, only by Mn. The Nb (oxy)nitride structures exhibit short Nb–Nb distances which indicates localised bonding between Nb atoms. Magnetic susceptibility and electrical conductivity measurements of the tetragonal phases at 15–300 K show, respectively, small magnetic moments which are coupled in an antiferromagnetic manner at low temperatures and poor, nearly temperature-independent, conductivities.
Place, publisher, year, edition, pages
1998. Vol. 278, no 1-2, 83-91 p.
Mn-Nb oxynitrides, Rietveld refinement, electron diffraction
Research subject Materials Chemistry
IdentifiersURN: urn:nbn:se:su:diva-43887DOI: 10.1016/S0925-8388(97)00496-9OAI: oai:DiVA.org:su-43887DiVA: diva2:371524