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• Description

  Gadolinum is found in minerals bastnasite and monazite, always associated with other rare earth metals. It was isolated from yttria in 1880 by the Swiss chemist Marignac, and discovered independently in 1885 by Boisbaudran. It was named in honor of the Swedish chemist Gadolin. Its abundance in the earth’s crust is 6.2 mg/kg and concentration in sea water is 0.7 ng/L.
  Gadolinium is also found in alloys and special minerals known as yttrium garnets. An alloy is made by melting and mixing two or more metals. The mixture has properties different from those of the individual metals. Gadolinium alloys are easier to work with than alloys without gadolinium. Gadolinium yttrium garnets are used in microwave ovens to produce the microwaves. Gadolinium metal is not especially reactive. It dissolves in acids and reacts slowly with cold water. It also reacts with oxygen at high temperatures.
  The most important application of this metal is as control rod material for shielding in nuclear power reactors. Its thermal neutron absorption cross section is 46,000 barns. Other uses are in thermoelectric generating devices, as a thermoionic emitter, in yttrium-iron garnets in microwave filters to detect low intensity signals, as an activator in many phosphors, for deoxidation of molten titanium, and as a catalyst. Catalytic applications include decarboxylation of oxaloacetic acid; conversion of ortho- to para-hydrogen; and polymerization of ethylene.
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• Uses

  Gadolinium oxide (Gd2O3) has multiple uses in medicine, chemical processes, electronics, and glass making. Gadolinium oxide is used in the creation of the phosphors used in television tubes as well as the creation of gadolinium yttrium garnets used in microwaves and materials used to absorb atomic reactions. Gadolinium has a shiny metallic lustre with a slight yellowish tint. It is both ductile and malleable.
  Gadolinium is utilized for both its high magnetic moment (7.94uB) and in phosphors and scintillated material. When mixed with EDTA dopants, it is used as an injectable contrast agent for patients undergoing magnetic resonance imaging. With its high magnetic moment, Gadolinium can reduce relaxation times and thereby enhance signal intensity.
  Gadolinium also possesses unusual metallurgic properties, with as little as 1% of Gadolinium improving the workability and resistance of Iron, Chromium, and related alloys to high temperatures and oxidation.
  Gadolinium compounds are also used for making green phosphors for color TV tubes.
  Gadolinium is used for making Gadolinium Yttrium Garnet (Gd:Y3Al5O12); it has microwave applications and is used in fabrication of various optical components and as substrate material for magneto-optical films.
  Gadolinium Metal is ferromagnetic, ductile and malleable metal, and widely used for making speciality alloys, MRI(magnetic Resonance Imaging), superconductive materials and magnetic refrigerator. Gadolinium is also used in nuclear marine propulsion systems as a burnable poison. In X-ray systems, gadolinium is contained in the phosphor layer, suspended in a polymer matrix at the detector. It is used for making Gadolinium Yttrium Garnet (Gd:Y3Al5O12); it has microwave applications and is used in fabrication of various optical components and as substrate material for magneto-optical films. Gadolinium Gallium Garnet (GGG, Gd3Ga5O12) was used for imitation diamonds and for computer bubble memory. It can also serve as an electrolyte in Solid Oxide Fuel Cells (SOFCs). ;

• Reactions

  The only oxidation state known for this metal is +3. Therefore, all its compounds are trivalent. It reacts with dilute mineral acids forming the corresponding salts. The reaction is vigorous but usually not violent.
  2Gd + 3H2SO4 → Gd2(SO4)3 + 3H2
  2Gd + 6HCl → 2GdCl3 + 3H2
  Although the metal is stable in air at ordinary temperature, it burns in air when heated at 150 to 180°C, particularly when present in sponge or powdered form having a large surface area. The product is gadolinium(III) oxide, Gd2O3.
  Gadolinium is a strong reducing agent. It reduces oxides of several metals such as iron, chromium, lead, manganese, tin, and zirconium into their elements. The standard oxidation potential for the reaction
  Gd → Gd3+ + 3e– is 2.2 volts.
  Gadolinium burns in halogen vapors above 200°C forming gadolinium(III) halides:
  2Gd + 3Cl2 → 2GdCl3
  When heated with sulfur, the product is gadolinium sulfide Gd2S3. Similarly, at elevated temperatures, gadolinium combines with other nonmetals such as nitrogen, hydrogen, and carbon forming nitride, hydride, and carbide respectively:
  2Gd + N2 → 2GdN
  2Gd + 3H2 → 2GdH3 ;

• Production Methods

  Gadolinium is produced from both its ores, monazite and bastnasite. After the initial steps of crushing and beneficiation, rare earths in the form of oxides are attacked by sulfuric or hydrochloric acid. Insoluble rare earth oxides are converted into soluble sulfates or chlorides. When produced from monazite sand, the mixture of sand and sulfuric acid is initially heated at 150°C in cast iron vessels. Exothermic reaction sustains the temperature at about 200 to 250°C. The reaction mixture is cooled and treated with cold water to dissolve rare earth sulfates. The solution is then treated with sodium pyrophosphate to precipitate thorium. Cerium is removed next. Treatment with caustic soda solution followed by air drying converts the metal to cerium(IV) hydroxide. Treatment with hydrochloric or nitric acid solGADOLINIUM 303ubilizes all rare earths except cerium. Rare earth salt solution is then treated with magnesium nitrate. The double salts of samarium, europium, and gadolinium nitrate crystallize out. Individual salts are separated by ion exchange methods.
  Gadolinium is obtained from its salts, usually its chloride or fluoride, by heating with excess calcium at 1,450°C under argon. The reduction is carried out in a tantalum crucible. Alternatively, fused gadolinium chloride mixed with sodium or potassium chloride is electrolyzed in an iron pot that serves as the anode and using a graphite cathode. Sponge gadolinium may be produced by reducing molten gadolinium chloride with a reducing metal oxide in vaporized state at a temperature below 1,300°C (the melting point of gadolium) at a reduced pressure. ;

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