Samarium

History

Occurence

• 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%.

Isolation

• 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 rectnly, 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.

Properties

• 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 922C. The metal ignites in air at about 150C.
• Twenty one isotopes of samarium exist.
• Natural samarium is a mixture of several isotopes, three of which are unstable with long half-lives.

Uses

• Samarium, along with other rare earths, is used for carbon-arc lighting for the motion picture industry.
• The sulfide has excellent high-temperature stability and good thermoelectric efficiencies up to 1100C.
• 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 masers 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.

Costs