Description
Barium selenide has the molecular formula of BaSe and the molecular weight of 216.2956 g/mol. Its CAS
number is 1304-39-8. It is a white crystalline powder
having a melting point of 1782°C. Its density is 5.02 g/cm
3. It reacts with water so that an aqueous
method of precipitation cannot be used to prepare
this compound. Barium selenide is very moisture
sensitive, and must be handled under inert conditions.
It can be prepared by reaction of the oxide or
carbonate with Se, or by the reduction of the selenate
with hydrogen gas:
2BaCO3+ 5Se+ Heat 2BaSe+ 3SeO2+ CO2
BaSeO4+ 4H2 BaSe+ 4H2O
Strontium selenide and barium selenide both have
a simple cubic structure, with cube edges equal to
3.117 and 3.308 , respectively.
Chemical Properties
Crystalline powder. Decomposes in water.
Uses
Barium selenide has been used to construct a photocell
that has been used extensively to measure the solar
irradiance of the Sun at various points on the globe. It is
used because other photocell elements like selenium
tend to decline in output and saturate under the intense
radiance of the Sun. BaSe remains quasi-linear and can
be used to measure intensity from 2000 to 7200
using a double monochrometer as a spectrum analyzer.
As a portable unit, it uses narrowband (20–50 halfwidth)
interference glass filters in 14 steps as a spectrum
analyzer over the range 3100 to 16,300 , but the
recording is manual. The field of view is <3° of the solar
irradiance over the face of the Sun.
BaSe is available commercially as a sputtering target
or in limited quantities as a powder.
Uses
In photocells, semiconductors.
Synthesis
BaSeO4 + 4 H2 = BaSe + 4 H2O
The selenate (about 1 g.) is distributed in a thin layer over a
quartz boat 10 cm. long and 1 cm. wide. The drying at 200°C is
repeated, this time in a reaction tube and in a stream of N2. Reduction in a stream of H2 follows. It should continue for two hours at 500°C
for BaSeO4.
