Zr
ZIRCONIUM
(Arabic zargun, gold color)
Zr at. wt. 91.22
at. no. 40
m.p. l852±20°C
b.p. 4377°C
sp. gr. 6.506 (20°C)
valence +2, +3, and +4.
Electronic configuration
| SHELL |
K |
L |
M |
N |
O |
P |
Q |
| SUB SHELL |
He |
Neon |
Argon |
Krypton |
Xenon |
Radon |
Eka-radon |
| 1s |
2s 2p |
3s 3p |
3d 4s 4p |
4d 5s 5p |
4f 5d 6s 6p |
5f 6d 7s 7p |
| Zirconium
|
1s22s22p63s23p63d104s24p64d25s2 |
|
|
| Symbol
|
2F2 |
Zirconium, or its variations, is mentioned in biblical writings. The name zirconium probably originated from the arabic word zargun, which
describes the color of the gemstone now known as zircon,
jargon, hyacinth, jacinth, or ligure. The mineral
was not known to contain a new element until Kiaproth,
in 1789, analyzed a jargon from Ceylon and found a new
earth, which Werner named zircon (silex circonius), and
Klaproth called Zirkonerde (zirconia). The impure metal
was first isolated by Berzelius in 1824 by heating a mixture
ofpotassium and potassium zirconium fluoride in a small iron
tube. Pure zirconium was first prepared in 1914. Very pure zir-
conium was first produced in 1925 by van Arkel and de Boer
by an iodide decomposition process they developed. Zirco-
nium is found in abundance in S-type stars, and has been
identified in the sun and meteorites. Preliminary analyses of
lunar rock samples obtained during the Apollo 11 mission to
the moon showed a surprisingly high zirconium oxide con-
tent, compared with terrestrial rocks. Naturally occurring zir-
conium contains five isotopes, one of which, Zr96 (abundant
to the extent of 2.80 %), is unstable with a very long half-life
of >3.6 x 1017 yrs. Fifteen other unstable nuclides and
isomers of zirconium have been characterized. Zircon,
ZrSiO4, the principal ore, is found in deposits in Florida,
South Carolina, Australia, and Brazil. Baddeleyite, found
in Brazil, is an important zirconium mineral. It is prin-
cipally pure ZrO2 in crystalline form having a hafnium
content of about 1 %. Zirconium also occurs in some 30 other
recognized mineral species. Zirconium is produced com-
mercially by reduction of the chloride with magnesium (the
Kroll Process), and by other methods. lt is a grayish-white
lustrous metal. When finely divided, the metal may ignite
spontaneously in air, especially at elevated temperatures.
The solid metal is much more difficult to ignite. The inherent
toxicity of zirconium compounds is low. Hafnium is in-
variably found in zirconium ores, and the separation is
difficult. Commercial-grade zirconium contains from I to
3 % hafnium. Zirconium has a low absorption cross section
for neutrons, and is therefore used for nuclear energy
applications, such as for cladding fuel elements. Zirconium
has been found to be extremely resistant to the corrosive
environment inside atomic reactors, and it allows neutrons
to pass through the internal zirconium construction material
without appreciable absorption of energy. Reactors of the
size now being made may use as much as a half-million lineal
feet of zirconium alloy tubing. Reactor-grade zirconium is
essentially free of hafnium. Zircaloy is an important alloy
developed specifically for nuclear applications. Zirconium
is exceptionally resistant to corrosion by many common
acids and alkalis, by sea water, and by other agents. It is used
extensively by the chemical industry where corrosive
agents are employed. Zirconium is used as a getter in vacuum
tubes, as an alloying agent in steel, in making surgical
appliances, photoflash bulbs, explosive primers, rayon
spinnerets, lamp filaments etc. It is used in poison ivy lotions
in the form of the carbonate as it combines with urushiol.
With columbium, zirconium is superconductive at low
temperatures and is used to make superconductive magnets,
which offer hope of direct large-scale generation of electric
power. Alloyed with zinc, zirconium becomes magnetic at
temperatures below 350K. Zirconium oxide (zircon) has a
high index of refraction and is used as a gem material. The
impure oxide, zirconia, is used for laboratory crucibles that
will withstand heat shock, for linings of metallurgical
furnaces, and by the glass and ceramic industries as a
refractory material. Its use as a refractory material accounts
for a large share of all zirconium consumed. Commercial
zirconium metal sponge is priced at about $5/lb. Fabricated
zirconium parts are higher in cost.
© 1999 F. Davies
Delphi O.E.M. Co.
All rights reserved
