Date of Award
Winter 3-19-2023
Degree Type
Thesis
Degree Name
Master of Science (MS)
Department
Physics
First Advisor
Susan M. Fischer, PhD
Second Advisor
Chris Goedde, PhD
Third Advisor
Gabriela B. Gonzalez Aviles, PhD
Abstract
The Crystal Structure of Hexagonal Molybdenum Oxynitride Hydride
The following thesis is a comprehensive study of the crystalline structure of a hexagonal molybdenum oxynitride hydride through the analysis of neutron and synchrotron x-ray diffraction patterns. This material is of interest for its tunable electrical, magnetic, thermal, and catalytic properties. It was hypothesized that the wet ammonolysis of a molybdenum oxide precursor could result in a hexagonal MoN phase. The composition of the powder sample was characterized using Prompt Gamma-ray Neutron Activation Analysis, Thermogravimetric Analysis, and Combustion Analysis. Neutron and x-ray diffraction measurements were conducted, as they complement each other, to obtain the full picture for the atomic arrangement of heavy and light atoms in the structure. The diffraction data were analyzed using the Rietveld Refinement method with the General Structure Analysis System II to determine the phase composition of the sample, the positions of the atoms, their thermal parameters, and their site occupation fractions within the unit cell. The δ3-MoN structure reported in the literature, having a hexagonal space group of P63mc, was used as the main phase for the refinement. In the current study, molybdenum atoms do not fully occupy the crystallographic sites indicating a small concentration of cation vacancies. There are two anion sites with nitrogen and oxygen as well as a hydrogen site making this sample an oxynitride hydride. The lattice parameters for this phase were a=5.7470(1) Å and c=5.62771(8) Å. Contrary to what has been reported in literature, two minor additional phases were also detected in the sample. Mo5N6 was considered as a candidate for one of the secondary phases. Two separate possibilities for this hexagonal phase are explored in this thesis: Space group P63/m and P63/mmc. The third phase is cubic Mo2N with space group Fm3m, which appears to be remnants from the wet ammonolysis reaction. The main hexagonal phase has a composition of MoN0.81(1)−0.82(2)O0.23(1)H0.16(1)−0.17(1). The total composition of the sample is MoN0.83(2)−0.86(1) O0.20(1)−0.21(1)H0.14(1)−0.15(1) .
Recommended Citation
Sinha, Shriya, "The Crystal Structure of Hexagonal Molybdenum Oxynitride Hydride" (2023). College of Science and Health Theses and Dissertations. 561.
https://via.library.depaul.edu/csh_etd/561
SLP Collection
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