Effect of nitrogen to niobium atomic ratio on superconducting transition temperature of δ-NbNx powders
Powders of cubic niobium nitride δ-NbN x with a particle size of below 20 μm were prepared by reactive diffusion at T = 1455−1475°C under nitrogen pressures of P 1 (N 2 ) = 0.1−3 MPa and P 2 (N 2 ) = 25 MPa. For these powders, the values of the stoichiometric coefficient x , lattice parameter a , an...
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| Published in | International journal of self-propagating high-temperature synthesis Vol. 19; no. 1; pp. 9 - 16 |
|---|---|
| Main Authors | , , , |
| Format | Journal Article |
| Language | English |
| Published |
Heidelberg
Allerton Press, Inc
01.03.2010
|
| Subjects | |
| Online Access | Get full text |
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| Summary: | Powders of cubic niobium nitride δ-NbN
x
with a particle size of below 20 μm were prepared by reactive diffusion at
T
= 1455−1475°C under nitrogen pressures of
P
1
(N
2
) = 0.1−3 MPa and
P
2
(N
2
) = 25 MPa. For these powders, the values of the stoichiometric coefficient
x
, lattice parameter
a
, and the superconducting transition temperature
T
c were measured and the
a
(
x
),
T
c
(
x
) and
T
c
(
a
) functions were analyzed. The
T
c
values were found to linearly grow with increasing a (decreasing structure imperfection). A maximum value of
T
c
(15.8 K) corresponded to a maximum value of
a
(4.3934 Å). Maximain the
a
(
x
) and
T
c
(
x
) curves were found to correspond to a slightly substoichiometric nitride with
x
= 0.98. Having synthesized cubic niobium nitrides with 0.892 <
x
< 1.062, we managed to measure the dependences of
a
and
T
c
on
x
all over the almost entire homogeneity range for δ-NbN
x
. Our
a
(
x
) and
T
c
(
a
) functions were found to reasonably agree with those previously reported for SHS-produced δ-NbN
x
powders. |
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| ISSN: | 1061-3862 1934-788X |
| DOI: | 10.3103/S1061386210010024 |