Gd - Gadolinium
|Chemical Element||Gadolinium||Melting Point °C||1313|
|Chemical Symbol||Gd||Boiling Point °C||3270|
|Atomic Number||64||Density g/cm3||7.9|
Gadolinium is a soft, shiny, silvery metal and a member of the lanthanoid group of the Periodic Table. It is the 41st most abundant element within the Earth’s crust and the 6th most abundant rare earth element. Gadolinium tarnishes very slowly in moist air, forming an oxide that flakes off the surface of the metal. When the oxide layer flakes off, fresh gadolinium is exposed to the air and the oxidisation process is continued. This metal reacts slowly with water and dissolves in acids.
Gadolinium was initially discovered by Jean Charles Galissard de Marignac in 1880. Marignac was analysing the supposed new element didymium, which he believed was not in fact a pure substance. This theory turned out to be true, and from a sample of didymium oxide, Marignac was able to extract a new rare earth. He named this new element alpha-yttrium. In 1886, this new element was also obtained by a man named Paul-Emile Lecoq de Boisbaudran, and it was he who suggested the name gadolinium, after the mineral gadolonite from which his sample had been obtained. The mineral itself was named after the Finnish chemist Johan Godolin.
Similarly to all the other rare earth elements, gadolinium is found in the ores monazite and bastnasite, although not in great quantities. Despit this, the main source of gadolinium is from China’s inner Mongolian mines. Monazite contains all of the rare earth elements and is mainly found in river sand in countries such as India, Brazil and South Africa. Bastnasite is mainly found in the Mojave desert in California. World production of gadolinium is said to be about 7,500 mt per year and is separated by ion exchange techniques. Although China is the main producing nation, gadolinium is also found in countries such as the USA, Brazil, India, Australia, Greenland and Tanzania. Global reserves of gadolinium are said to be in excess of 1 million tonnes.
Gadolinium has the greatest ability to capture thermal neutrons of all known elements, and therefore, has various nuclear industry applications. In nuclear energy production, Gadolinium is used as a ‘burnable poison’, especially in boiling water reactors, to even out the performance of the reactor over time. Gadolinium oxide is a neutron absorber, which decays under neutron exposure, compensating for the progressive build up of other absorbers as the uranium oxide fuel is used up. Gadolinium is also the most efficient element used to detect power plant radiation leaks.
Due to its unique magnetic properties and use in alloys, gadolinium has a number of other specialised uses. It is used in magnetic refrigeration to significantly reduce carbon dioxide emissions, due to increased energy efficiency. Optical lenses containing gadolinium are used for magneto-optical and electro-optical systems. In medicine, gadolinium is used in MRIs to provide better imaging of tumours. It is also used in electronic ceramics, glasses, lasers, magnetic recording and crystal scintillators. Gadolinium is used with yttrium to form garnets that have microwave applications. It can also be alloyed with certain metals, such as iron and chromium, to improve their workability and resistance to high temperatures and oxidation. Gadolinium compounds are also used to make phosphors for colour televisions.
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- Stwertka, Albert. A Guide to the Elements, 3rd Edition, Oxford University Press, 2012