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Tellurium
(Te) was discovered in 1783 by Baron Franz Josef Müller von Reichenstein
in Sibiu, Roumania. Tellurium is a silvery-white, metallic-looking in
bulk, but is usually obtained as a dark grey powder. It is a semi-metal.
Tellurium burns in air or oxygen, is unaffected by water or HCl, but
dissolves in HNO3. It is used in alloys to improve machinability,
in electronics, and in catalysts.
Tellurium has p-type semiconductor properties and, hence, it
is used in the electronics industry. Tellurium compounds (tellurides)
are semiconducting materials and used for photoreceptors in solar cells.
Te is also used in the refining of zinc where it eliminates cobalt from
the process. Contact with either the pure metal or its compounds is
to be avoided as they are not only toxic, but inhalation of the vapours
leads to unpleasant body odors! |
Main
properties:
| Transparency
range, µm |
3.5 - 36 |
| Point group |
32m |
| Lattice parameters,
Å |
a = 4.495,
b = 3.74, c = 5.912 |
| Mohs hardness |
2.3 |
| Density,
g/cm3 |
6.25@ 20°C |
| Melting point
(°C ) |
450 |
| Refractive
indexes: |
- |
at
5.0 µm |
no
= 4.864; ne = 6.316 |
| at
10.6 µm |
no
= 4.792; ne = 6.247 |
| at
14.0 µm |
no
= 4.775; ne = 6.230 |
| at
28.0 µm |
no
= 4.716; ne = 6.183 |
| Non-linear
coefficient at 10.6 µm, pm/V |
d11
= 650 |
| Optical damage
threshold, MW/cm2 |
20 - 40 (at
10.6 µm, 150 ns) |
| Thermal expansion
coefficient , at 293 °K: |
- |
parallel
to z-axis |
1.6 x 10-6
x °K -1 |
| perpendicular
to z-axis |
27.2 x 10-6
x °K -1 |
| Thermal conductivity,
mW x cm-1 x °K -1 |
4000 |
| Orientation
of single crystal |
(0001), (1100)
or (11-20) |
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