Gadolinium

History

Occurence

• Gadolinium is found in several other minerals, including monazite and bastnasite, which are of commercial importance.
• The element has been isolated only in recent years.
• With the development of ion-exchange and solvent extraction techniques, the availability and price of gadolinium and the other rare-earth metals have greatly improved.
• Seventeen isotopes of gadolinium are now recognized; seven occur naturally.

Properties

• The metal can be prepared by the reduction of the anhydrous fluoride with metallic calcium.
• As with other related rare-earth metals, it is silvery white, has a metallic luster, and is malleable and ductile.
• At room temperature, gadolinium crystallizes in the hexagonal, close-packed alpha form.
• Upon heating to 1235C, alpha gadolium transforms into the beta form, which has a body-centered cubic structure.
• The metal is relatively stable in dry air, but in moist air it tarnishes with the formation of a lossely adhering oxide film which spalls off and exposes more surface to oxidation.
• The metal reacts slowly wiht water and is soluble in dilute acid.
• Gadolinium has the highest thermal neutron capture cross-section of any known element (49,000 barns).

Isotopes

• Natural gadolinium is a mixture of seven isotopes.
• Two of these, 155Gd and 157Gd, have excellent capture characteristics, but they are present naturally in low concentrations.
• As a result, gadolinium has a very fast burnout rate and has limited use as a nuclear control rod material.

Uses

• It has been used in making gadolinium yttrium garnets, which have microwave applications.
• Compounds of gadolinium are used in making phosphors for color TV tubes.
• The metal has unusual superconductive properties.
• As little as 1% gadolinium has been found to improve the workability and resistance of iron, chromium, and related alloys, to high temperatures and oxidation.
• Gadolinium ethyl sulfate has extremely low noise characteristics and may find use in duplicating the performance of amplifiers, such as the maser.
• The metal is ferromagnetic. Gadolinium is unique for its high magnetic moment and for its special Cuire temperature (above which ferromagnetism vanishes) lying just a room temperature.
• The suggests uses as a magnetic component that senses hot and cold.

Costs