Synthesis of cubic niobium nitride by reactive diffusion under nitrogen pressure
- Institute of Structural Macrokinetics and Materials Science (ISMAN), Russian Academy of Sciences, Chernogolovka, Moscow 142432 (Russian Federation)
- Institut Charles Gerhardt Montpellier (ICGM), PMOF-UM2-CNRS, pl. E. Bataillon, 34095 Montpellier Cedex 5 (France)
The synthesis of niobium nitride by reactive diffusion in a furnace at 1395-1475 deg. C and under nitrogen pressure in the range 2-25 MPa was investigated. In experiments, we used compacted Nb powder with a mean particle size of 43 {mu}m. Phase transformations in the product as studied by electron probe microanalysis (EPMA) were found to proceed in the following order: Nb {yields} {alpha}-Nb(N) {yields} {beta}-Nb{sub 2}N{sub 1{+-}}{sub x} {yields} {gamma}-Nb{sub 4}N{sub 3{+-}}{sub x} {yields} {delta}-NbN{sub 1{+-}}{sub x}. The size of niobium particles which could react with nitrogen to yield cubic niobium nitride was estimated (SEM analysis) from the dependence of the thickness {delta} of the {delta}-NbN{sub 1{+-}}{sub x} outer layer formed on the surface of Nb particles on the dwell time t{sub dw} at 1460-1473 deg. C. It was shown that {delta} grew nearly proportional to t{sub dw}. At t{sub dw} = 30 min and P(N{sub 2}) = 2 MPa, {delta} was found to attain a value of about 15.5 {mu}m. Prolonged heating (t{sub dw} {approx} 60 min) was found to result in decomposition of the single-phase cubic niobium nitride into a two-phase (multiphase) product. This was confirmed by XRD data and magnetic measurements which showed the occurrence of two different critical temperatures T{sub c} in the same sample. The maximum critical temperature T{sub c} was found to attain a value of 15.6 K.
- OSTI ID:
- 21199758
- Journal Information:
- Materials Research Bulletin, Vol. 44, Issue 5; Other Information: DOI: 10.1016/j.materresbull.2008.11.008; PII: S0025-5408(08)00386-3; Copyright (c) 2008 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0025-5408
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CRITICAL TEMPERATURE
CUBIC LATTICES
DECOMPOSITION
DIFFUSION
ELECTRON MICROPROBE ANALYSIS
HEATING
LAYERS
MICROSTRUCTURE
NIOBIUM NITRIDES
NIOBIUM-ALPHA
NITROGEN
PARTICLE SIZE
PHASE TRANSFORMATIONS
PRESSURE RANGE MEGA PA 10-100
SCANNING ELECTRON MICROSCOPY
SURFACES
SYNTHESIS
TEMPERATURE RANGE 1000-4000 K
X-RAY DIFFRACTION