The abbreviation SmCo stands for an alloy of samarium and cobalt. The German mineralogist Heinrich Rose, who in turn named it after the Russian mining engineer Vasily Samarsky-Bychovets, discovered the silvery shining element Samarium. The metal belongs to the rare earths; it is still only won in China up until today.
Cobalt belongs to the element category of transition metals, more specifically; it is a ferromagnetic transition metal with a Curie temperature of 1150 ° C. The steel gray, extremely tough heavy metal is suitable as a good conductor for heat and electricity.
The use of SmCo
Samarium cobalt is primarily used for various permanent magnets. Two crystal structures, on the one handSmCo5
and on the otherSm2Co17 (with iron, copper or zirconium as additional alloying elements),
come into question for the application. The two forms of alloy were developed in 1966 and 1972, and were the materials with the highest magnetic energy density known until the discovery of neodymium-iron-boron in 1982.
Due to their properties, permanent magnets made of SmCo are difficult to demagnetize and retain their magnetic forces up to an operating temperature of 450 ° C. Since the temperature coefficient of remanence is very low, the magnetic field loses only a slight effect per degree of temperature rise. Furthermore, thanks to their high coercivity, they are extremely resistant to demagnetizing fields and have enormous corrosion resistance.
Since the elements used rarely occur on Earth, the price for strong SmCo magnets is relatively high. In addition, you have to handle them with care, as it comes with this brittle material relatively quickly to flaking. There is also a relatively complicated manufacturing process.
For this purpose, samarium and cobalt must be melted under a special protective gas atmosphere (argon). The resulting alloy is pulverized after cooling. Now the powder is baked together at a temperature of 1150 to 1250 ° (sintering process). In the course of this process, the material must be converted to the desired starting form, as subsequent processing is no longer possible.