Sm - Samarium

Properties

Samarium is a silvery-white metal and a member of the lanthanoid group of the Periodic Table and the 40th most abundant element within the Earth’s crust. Samarium is stable in dry air, but in moist air an oxide layer forms. This metal will ignite spontaneously at temperatures as low as 150°C. Samarium has strong magnetic properties and mixed with cobalt makes permanent magnets, second only to neodymium magnets in strength.

History

Samarium was discovered in 1879 by the French chemist, Paul-Emile Lecoq de Boisbaudran. Boisbaudran was able to extract the mixture didymium from a sample of samarskite. Whilst analysing this didymium, he noticed that there was a 2nd signature present. He was able to separate the two, and measure the 2nd spectrum. This proved to be the hydroxide of a new element, which he named samarium after the mineral, samarskite, in which he found it.

Sources

Samarium is found in the minerals monazite and bastnasite that contain all rare earth elements. These ores are mined in China, USA, Brazil, India, Sri Lanka and Australia.  Monazite contains 3% by weight of samarium.  There are thought to be around 2 million tonnes of reserves worldwide, with only 700 tonnes per year being extracted worldwide.  Commercially, samarium is extracted by electrolysis of the molten chloride with sodium chloride.  It can also be produced by heating samarium oxide with barium or lanthanum, which drives off the samarium as a vapour.

Uses

Samarium is used in permanent magnets (alloyed with cobalt), which are 10,000 times more powerful than iron, and have the highest resistance to demagnetization of any material, as they can withstand temperatures of over 700°C.  Their strength makes them particularly useful for the miniaturization of devices, such as headphones and motors.  Samarium oxide is used in ceramics and making glass that absorbs infrared rays.  Samarium is also used as a catalyst to aid conversion of ethanol to ethane, and as a neutron absorber for control rods, which regulate reactor cores in nuclear power plants.

Soluble samarium salts are mildly toxic by ingestion and may cause skin and eye irritation.  Samarium is no threat to plants or animals.