Rare Earths



Gadolinium (Gd, atomic number 64) rare earth metal is obtained from the mineral gadolinite. Gadolinia, the oxide of gadolinium, was separated by Merignac in 1880 and Lecoq de Boisbaudran independently isolated it from Mosasander’s yttria in 1886. Gadolinium is found in several other minerals, including monazite and bastnasite. With the development of ion-exchange and solvent extraction techniques, the availability and the prices of gadolinium and the other rare earth metals have greatly improved. The metal can be prepared by the reduction of the anhydrous fluoride with metallic calcium. Gadolinium is silvery white, has a metallic luster and is malleable and ductile (like other related rare earth metals). At room temperature gadolinium crystallizes in the hexagonal, close packed alpha form. Upon heating to 1235 degrees Celsius, alpha gadolinium transforms into the beta form (which has a body centered cubic structure). The metal is relatively stable in dry air but tarnishes in moist air. It forms a loosely adhering oxide film which falls off and exposes more surface to oxidation. The metal reacts slowly with water and is soluble in dilute acid. Gadolinium has the highest thermal neutron capture cross-section of any known element (49,000 barns).

Some known uses for Gadolinium are as follows:

  • MRI tests- gadolinium changes the way water molecules react in your body when scanned allowing the contrast between healthy and non healthy tissue to be seen.
  • Microwaves- gadolinium yttrium garnets are used in microwave applications.
  • Color Television_ gadolinium compounds are used as phosphors in color televisions.
  • The unusual superconductive properties improve the workability and resistance of iron and chromium and related alloys to high temperatures and oxidation (as little as 1% gadolinium is needed).
  • Duplicating performance of amplifiers such as the maser- gadolinium ethyl sulfate ahs extremely low noise characteristics and may find use in duplicating the performance.
  • Magnetic component that can sense hot and cold- gadolinium metal is ferromagnetic. It is unique for its high magnetic movement and for its special Curie temperature (above which ferromagnetism vanishes) lying at room temperature. Therefore it can be used as a magnetic component that can sense hot and cold.