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Title: Synthesis and characterization of novel group VI metal (Mo, W) nitride and oxide compounds

Abstract

Investigations into the preparation of tungsten nitrides have involved the synthesis of molecular precursors, and their conversion to tungsten nitrides at relatively low temperatures. Two interesting molecular precursors, [WNCl 3∙NCCH 3] 4 and WN(N 3) 3∙xNCCH 3, have been prepared and characterized. The molecular structure of the first consists of a W 4N 4 tetrameric core with multiple and single W-N bonds arranged in an alternating fashion. Three new solid state phases, amorphous W 3N 5, cubic WN, and W 2N 2(C 2N 2), have been discovered by solid state and chemical vapor transport reactions. The structures have been investigated. A systematic study in the Ln 2O 3-MoO 3-Mo (Ln = La, Ce, Pr, Nd, Sm) system has been explored to better understand LnMo 8O 14. The study has shown that the sizes of the rare-earth cations affect the formation of these phases. Larger cations (La, Ce, and Pr) aid in the formation of trans-Mo 8 bicapped octahedra, and the smaller cations (Nd, Sm) only stabilize the cis-Mo 8 bicapped octahedra. Magnetic susceptibility measurements have indicated that no effective moment contribution arises from the Mo 8 metal clusters, even though the cis-Mo 8 cluster in LnMo 8O 14, containing allmore » cis-Mo 8 octahedra, apparently contains an odd number of electrons (23). Electrical resistivity measurements and electronic structure calculations have shown that the LnMo 8O 14 compounds containing cis-Mo 8 clusters are metallic, and the LnMo 8O 14 compounds containing a 1:1 ratio of cis- to trans-Mo 8 clusters are semiconducting.« less

Authors:
 [1]
  1. Iowa State Univ., Ames, IA (United States)
Publication Date:
Research Org.:
Ames Lab., IA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
587893
Report Number(s):
IS-T-1829
ON: DE98004649; TRN: 98:009463
DOE Contract Number:  
W-7405-ENG-82
Resource Type:
Thesis/Dissertation
Resource Relation:
Other Information: TH: Thesis (Ph.D.); PBD: 23 Feb 1998
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; TUNGSTEN NITRIDES; LANTHANUM OXIDES; MOLYBDENUM OXIDES; CERIUM OXIDES; NEODYMIUM OXIDES; SAMARIUM OXIDES; PRASEODYMIUM OXIDES; PRECURSOR; MOLECULAR STRUCTURE; FABRICATION; MAGNETIC SUSCEPTIBILITY; ELECTRIC CONDUCTIVITY; PHASE STUDIES

Citation Formats

Zhang, Zhihong. Synthesis and characterization of novel group VI metal (Mo, W) nitride and oxide compounds. United States: N. p., 1998. Web. doi:10.2172/587893.
Zhang, Zhihong. Synthesis and characterization of novel group VI metal (Mo, W) nitride and oxide compounds. United States. doi:10.2172/587893.
Zhang, Zhihong. Mon . "Synthesis and characterization of novel group VI metal (Mo, W) nitride and oxide compounds". United States. doi:10.2172/587893. https://www.osti.gov/servlets/purl/587893.
@article{osti_587893,
title = {Synthesis and characterization of novel group VI metal (Mo, W) nitride and oxide compounds},
author = {Zhang, Zhihong},
abstractNote = {Investigations into the preparation of tungsten nitrides have involved the synthesis of molecular precursors, and their conversion to tungsten nitrides at relatively low temperatures. Two interesting molecular precursors, [WNCl3∙NCCH3]4 and WN(N3)3∙xNCCH3, have been prepared and characterized. The molecular structure of the first consists of a W4N4 tetrameric core with multiple and single W-N bonds arranged in an alternating fashion. Three new solid state phases, amorphous W3N5, cubic WN, and W2N2(C2N2), have been discovered by solid state and chemical vapor transport reactions. The structures have been investigated. A systematic study in the Ln2O3-MoO3-Mo (Ln = La, Ce, Pr, Nd, Sm) system has been explored to better understand LnMo8O14. The study has shown that the sizes of the rare-earth cations affect the formation of these phases. Larger cations (La, Ce, and Pr) aid in the formation of trans-Mo8 bicapped octahedra, and the smaller cations (Nd, Sm) only stabilize the cis-Mo8 bicapped octahedra. Magnetic susceptibility measurements have indicated that no effective moment contribution arises from the Mo8 metal clusters, even though the cis-Mo8 cluster in LnMo8O14, containing all cis-Mo8 octahedra, apparently contains an odd number of electrons (23). Electrical resistivity measurements and electronic structure calculations have shown that the LnMo8O14 compounds containing cis-Mo8 clusters are metallic, and the LnMo8O14 compounds containing a 1:1 ratio of cis- to trans-Mo8 clusters are semiconducting.},
doi = {10.2172/587893},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1998},
month = {2}
}

Thesis/Dissertation:
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