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An Overview of Gadolinium

The oxide of gadolinium, gadolinia, was separated by Marignac in 1880 and it was Lecoq de Boisbaudran who independently isolated the element from Mosander’s “yttria” in 1886. Gadolinium is found in several minerals. The two of commercial importance are monazite and bastnasite. Seventeen (17) isotopes of gadolinium are now recognised, seven (7) of which occur naturally.

The metal may be prepared the reduction of the anhydrous fluoride with metallic calcium. The metal has a silvery white appearance with a metallic lustre. It is ductile and malleable. Gadolinium metal is ferromagnetic.

Gadolinium (Gd) has two temperature dependant crystal structures, at room temperature it crystallises in the hexagonal, close-packed α form. Upon heating to 1235°C, α gadolinium transforms into the β form, which has a body-centred cubic structure.

Gadolinium metal is relatively stable in dry air, however in moist air it tarnishes with and forms a loose oxide film, which spalls off, and exposes fresh metal to oxidation. In water it reacts slowly and is soluble in dilute acid.

Gadolinium has the highest thermal neutron capture cross-section of any know element (49 000 barns.). However, gadolinium has a very fast burnout rate and for this reason has limited use as a nuclear control rod material.

Applications

Gadolinium has been used in making gadolinium yttrium garnets, which are useful in microwave and superconducting applications.

Gadolinium compounds are used in making phosphors for colour TV tubes. As an alloy element for improved workability and resistance to high temperature oxidation in iron, chromium, and their related alloys.

Gadolinium ethyl sulphate has extremely low noise characteristics and could be used to duplicate the performance of h.f. amplifiers, such as the maser.

Because gadolinium is ferromagnetic and has a very high magnetic moment coupled with its special Curie temperature (above which ferromagnetism ceases), which lies at room temperature. Gadolinium may be used as a magnetic component that senses hot and cold fluctuations.

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