The existence of gadolinium was first noted by the Swiss chemist Jean Charles Galissard de Marignac in 1880 in the mineral samarskite. The element was eventually named after Johan Gadolin, a Finnish chemist, whose name was also given to another rare earth mineral, gadolinite. Today, gadolinium is primarily obtained from ion adsorption clays in China and less so from the minerals xenotime, monazite and bastnaesite.
Gadolinium is a silvery white, malleable and ductile metal with a metallic lustre. Unlike other rare earth elements, gadolinium metal is relatively stable in dry air. It does however tarnish quickly in moist air, forming a loosely-adhering oxide which flakes off, and exposes the underlying surface to further oxidation. It is weakly magnetic, or paramagnetic, at room temperature, but becomes strongly magnetic or ferromagnetic below room temperatures. Gadolinium, particularly in alloy form, demonstrates a magneto caloric effect whereby its temperature increases when it enters a magnetic field and decreases when it leaves the magnetic field.
Applications of Gadolinium:
- Materials and Electronics: Gadolinium is used in making gadolinium yttrium garnets, which have microwave applications, and gadolinium compounds are used for making phosphors for colour TV tubes. Gadolinium is also used for manufacturing compact discs and computer memory.
- Alloys: Gadolinium possesses unusual metallurgic properties; as little as 1% of gadolinium improves both the workability of iron, chromium and related alloys and raises their resistances to high temperature oxidation. Future applications may include its use as a magnetic component for sensing hot and cold.
- Medical: Solutions of organic gadolinium complexes and gadolinium compounds are used as intravenously administered, contrasting agents to enhance images in medical magnetic resonance imaging (MRI). Gadolinium is also used in X-ray imaging where terbium-doped, gadolinium oxysulfide as a phosphor converts the X-rays released from a source into light. Because it has a high neutron capture cross-section, gadolinium is very effective for use with neutron radiography.
- Specialty Glass: Gadolinium gallium garnet is used in fabrication of various optical components and as substrate material for magneto-optical films.
- Energy: Gadolinium is used in nuclear marine propulsion systems as a burnable nuclear poison and as a secondary, emergency shut-down measure in some nuclear, particularly CANDU type, reactors.