Electrochemical synthesis of ceramic materials. 3. Synthesis and characterization of a niobium nitride precursor and niobium nitride powder
- Texas A M Univ., College Station, TX (United States)
- Univ. of New Mexico, Albuquerque, NM (United States)
- Los Alamos National Lab., NM (United States)
Anodic dissolution of Nb foil in an electrolyte solution containing liquid NH[sub 3] and NH[sub 4]Br produces an insoluble precursor that can be calcined to yield phase-pure NbN. Infrared spectroscopy is consistent with a precursor having the general formula NbX[sub n](NH[sub 2])[sub 5-n][center dot]pNH[sub 3]. By changing the calcination conditions, the phase of the resulting NbN powder can be varied. For example, calcining in pure Ar yields the superconducting [delta]-NbN phase at 600 and 800 [degrees]C but results in [gamma]-NbN at 1000 [degrees]C. A mixed 85% Ar/15% H[sub 2] calcining atmosphere also results in [delta]-NbN at 600 [degrees]C, but yields [gamma]-NbN phases at 800 [degrees]C. When the precursor powder is calcined in NH[sub 3] at 600, 800, or 1100 [degrees]C [approximately]-NbN phases result, but subsequent calcining in Ar at 1450 [degrees]C yields superconducting [delta]-NbN (Tc = 14.75 K). The calcination ambient affects the chemical composition of the powder: in all cases more reducing conditions lower the level of Br contamination. 42 refs., 8 figs., 1 tab.
- OSTI ID:
- 6837053
- Journal Information:
- Chemistry of Materials; (United States), Vol. 6:1; ISSN 0897-4756
- Country of Publication:
- United States
- Language:
- English
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