Description
Barium nitride purportedly has the molecular
formula of Ba3N2 and the molecular weight of
439.9944 g/mol. Its CAS number is 12047-79-9. It is
offered for sale by several reputable manufacturers but
the actual composition and identity may not coincide
with the formula presented. Although Mg, Ca (and to
some extent Sr) forms a number of compounds based
upon the general formula M3N2, there is no report in
the literature that or Ba forms such compositions. The
literature is devoid of any data relating to Ba3N2 and
the subnitride is mentioned only in the presence of Sr2N.
Barium nitride has been reported to be metastable
and sublimes in the 915 to 1050 C temperature range.
The reported equation for this behavior is: log
P = 6.38 × 10
4/T(K) and it decomposes when heated
beyond this range to form the metal and nitrogen gas,
i.e. it is metastable. Thus, the existence of barium nitride
is doubtful and no report of its formation or properties
exists to date.
Physical properties
Barium–nitride–hydride is one of the fewdocumented
H
--ionic conductors. It crystallizes in the a-NaFeO2
structure (space group R
m) with distorted Ba-octahedra
centered alternately by H
- and N
3-. Neutron diffraction
shows that the hydrogen ions are distributed independent
of temperature over lattice sites: 85% on (3a) and
15% on (6c). At T > 525 K a sharp increase of the ionic
conductivity can be observed. The diffusion process
takes place by uncorrelated jumps of hydrogen ions
between regular lattice sites. Using quasielastic neutron
scattering techniques and a planar jump diffusion model,
we were able to determine the mean residence time on
a H
--site to be s = 20 ± 2d ps and the diffusion constant
D to be 2.1×10
-5 cm
2/s at T = 823 K.
Ba2Nhas been used to produce other subnitrides. Bulk
thermal or filament-initiated reactions of mixed powders
of transition metal chlorides and Ba3N2 produces transition
metal nitrides (TiN, ZrN, HfN, VN, V2N) in good
yield. The products were characterized by X-ray powder
diffraction, SEM/EDAX, FT-IR, microelemental analysis
and imaging XPS. The effect of diluting the reaction by
the addition of LiCl was used to lower reaction temperatures
and in the case of WCI4 and Li3N produced WN.
Reaction propagation was investigated by using various
mixtures of nitriding reagent (Li3N, Mg3N2, Ca3N2), this
was correlated with T
ad(s), the maximum adiabatic
combustion temperature for salt formation only.
Uses
Barium nitride is a ceramic that finds use as a dopant in optical materials such as white emitting LEDs. Ba
3N
2 is also used as a synthetic precursor for ternary metal nitrides and as a flux growth medium for GaN.
Safety Profile
A poison by ingestion. Flammableby spontaneous chemical reaction with water to liberateexplosive ammonia gas. Dangerous; explodes uponheating and by spontaneous chemical reaction, liberatingNH3 vapor which can form explosive mixtures with air.Violent
