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. 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. 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.
It is used in infrared absorbing glass and as a neutron absorber in nuclear reactors.