||(Samarskite, a mineral) Discovered
spectroscopically by its sharp absorption lines in 1879 by Lecoq de
Boisbaudran in the mineral samarskite, named in honor of a Russian mine
official, Col Samarski.
||Samarium is found along with other members
of the rare-earth elements in many minerals, including monazite and
bastnasite, which are commercial sources. It occurs in monazite to the
extent of 2.8%. While misch metal containing about 1% of samarium metal,
has long been used, samarium has not been isolated in relatively pure
form until recent years. Ion-exchange and solvent extraction techniques
have recently simplified separation of the rare earths from one another;
more recently, electrochemical deposition, using an electrolytic
solution of lithium citrate and a mercury electrode, is said to be a
simple, fast, and highly specific way to separate the rare earths.
Samarium metal can be produced by reducing the oxide with lanthanum.
||Samarium has a bright silver luster and is
reasonably stable in air. Three crystal modifications of the metal
exist, with transformations at 734 and 922oC.
The metal ignites in air at about 150oC.
The sulfide has excellent high-temperature stability and good
thermoelectric efficiencies up to 1100oC.
||Twenty one isotopes of samarium exist.
Natural samarium is a mixture of several isotopes, three of which are
unstable with long half-lives.
||Samarium, along with other rare earths, is
used for carbon-arc lighting for the motion picture industry. SmCo5
has been used in making a new permanent magnet material with the highest
resistance to demagnetization of any known material. It is said to have
an intrinsic coercive force as high as 2200 kA/m. Samarium oxide has
been used in optical glass to absorb the infrared. Samarium is used to
dope calcium fluoride crystal for use in optical lasers or lasers.
Compounds of the metal act as sensitizers for phosphors excited in the
infrared; the oxide exhibits catalytic properties in the dehydration and
dehydrogenation of ethyl alcohol. It is used in infrared absorbing glass
and as a neutron absorber in nuclear reactors.
||The metal is priced at about $5/g.
||Little is known of the toxicity of
samarium; therefore, it should be handled carefully.
Source: Los Alamos National Laboratory