Properties and Overview of Samarium

Overview:

Samarium (Sm) is a chemical element with the symbol Sm and atomic number 62. It is part of the lanthanide series, a group of elements known as rare earth metals, which occupy the f-block of the periodic table. Discovered in 1879 by the French chemist Paul-Émile Lecoq de Boisbaudran, samarium was named after the mineral samarskite, from which it was first isolated. Samarium is relatively abundant in the Earth's crust, with an average concentration of about eight parts per million, making it more common than metals like tin. It is typically found in minerals such as monazite and bastnäsite, the primary sources of rare earth elements. Physically, samarium is a silvery-white metal that is moderately hard and has a density of 7.52g/cm³. It has a melting point of 1,072°C and a boiling point of 1,791°C, making it relatively stable at high temperatures compared to other lanthanides. Samarium has a hexagonal crystal structure and exhibits moderate malleability and ductility, meaning it can be deformed and stretched into thin wires without breaking. When exposed to air, samarium slowly oxidizes, forming a protective oxide layer that prevents further corrosion. However, it oxidizes more readily than some rare earth elements, which requires storing it under oil or in an inert atmosphere to prevent degradation.
Chemically, samarium is a reactive metal that readily forms compounds with most nonmetals. It exhibits oxidation states of +2 and +3, with +3 being the most stable and common. In the +3 oxidation state, samarium forms various compounds, including oxides, halides, and sulfides. One of the most notable compounds of samarium is samarium(III) oxide (Sm₂O₃), a pale yellow solid that is used in ceramics and glass production. Samarium also forms halides, such as samarium(III) chloride (SmCl₃) and samarium(III) fluoride (SmF₃), which are used as precursors in chemical syntheses and for doping materials to modify their properties. In the +2 oxidation state, samarium forms compounds such as samarium(II) iodide (SmI₂), which is a powerful reducing agent widely used in organic chemistry for various synthetic reactions, including carbon-carbon bond formation and the reduction of functional groups. This diverse range of chemical reactivity makes samarium valuable in academic research and industrial applications.
Regarding safety, samarium and its compounds are considered low to moderate toxicity. When handled properly, The metal poses little risk, but its dust and powder forms can be flammable and reactive, especially when exposed to moisture or air. The main health risk associated with samarium is inhalation or ingesting its dust or soluble compounds, which can cause respiratory and digestive tract irritation. Long-term exposure to high concentrations of samarium compounds can lead to liver and lung damage. However, such cases are rare and typically limited to occupational settings where strict safety guidelines may not be followed. In laboratory and industrial settings, safety measures such as using fume hoods, wearing protective clothing, and ensuring proper ventilation are essential to minimize exposure to samarium dust and compounds.

Production:

Samarium is primarily produced from monazite and bastnäsite through a series of steps that involve crushing the ore, separating the rare earth elements by solvent extraction, and then reducing the samarium oxide with calcium or lanthanum to produce metallic samarium. The production process also involves electrolysis in a molten salt bath, which helps obtain high-purity samarium metal. Depending on its intended application, the purified metal is then processed into various forms, such as ingots, powders, and alloys. Due to its relatively high abundance among rare earth elements, the production of samarium is not as economically challenging as that of some rare earth metals, and it is available in sufficient quantities to meet industrial demand.

Applications:

Samarium has a variety of applications across different industries, primarily due to its magnetic, electronic, and optical properties. One of its most significant uses is in producing samarium-Cobalt (SmCo) permanent magnets, known for their high magnetic strength, resistance to demagnetization, and stability at high temperatures. These magnets are widely used in applications requiring reliable performance under extreme conditions, such as electric motors, aerospace components, and military technologies. Samarium-cobalt magnets were among the first rare earth magnets to be developed and remain essential in industries where high-performance, lightweight, and compact magnetic materials are needed.
In addition to its use in magnets, samarium plays a role in various nuclear applications. Samarium-149, a naturally occurring isotope, is an effective neutron absorber, making it valuable as a control material in nuclear reactors to regulate the rate of fission. Another isotope, samarium-153, is used in medicine, particularly cancer treatment, for pain relief in patients with bone metastases. Samarium-153 is employed in a radiopharmaceutical known as samarium-153 lexidronam, which targets bone tissue and delivers targeted radiation therapy to reduce pain and improve the quality of life for cancer patients.
Samarium is also used in materials science and catalysis. In materials science, it is used to improve the performance of ceramics and glasses, where it helps increase thermal resistance and strength. Samarium-doped glass is used in laser applications, where its specific optical properties are valuable in producing high-precision and high-power lasers. In catalysis, samarium compounds, particularly samarium diiodide (SmI₂), are widely used as reducing agents in organic synthesis. This reagent is highly effective for a range of chemical reactions, including reducing ketones, aldehydes, and nitro compounds, as well as coupling reactions that form carbon-carbon bonds.

Summary:

Samarium is a versatile element with a wide range of physical, chemical, and nuclear properties, making it valuable in various technological and industrial applications. Its role in developing permanent magnets, its use in nuclear technology, and its contributions to materials science and organic chemistry highlight its importance as a functional material in modern science and technology. While safety considerations are necessary when handling samarium and its compounds, it remains a relatively accessible and manageable element in laboratory and industrial settings. As research continues into new materials and technologies, samarium's unique properties will likely lead to further future innovations and applications.

See a comprehensive list of atomic, electrical, mechanical, physical and thermal properties for samarium below: