7440-54-2 Usage
Description
Gadolinium is a rare-earth element with the symbol Gd and atomic number 64. It is a soft, silvery-white, ductile, and malleable metal with a metallic luster. Gadolinium is the second element of the dysprosium subgroup in the middle of the lanthanide series. It tarnishes in air, forming the oxide (Gd2O3) on the surface, which flakes off, exposing a fresh metal that in turn oxidizes. Its melting point is 1,313°C, its boiling point is 3,273°C, and its density is 7.90g/cm3. Gadolinium is the 40th most abundant element on Earth and the sixth most abundant of the rare-earths found in the Earth's crust (6.4 ppm). It is found in minerals such as bastnasite, monazite, and gadolinite, and is associated with other rare earth metals.
Uses
Used in Medical Applications:
Gadolinium is used as an injectable contrast agent for patients undergoing magnetic resonance imaging (MRI) when mixed with EDTA dopants. Its high magnetic moment allows it to reduce relaxation times and enhance signal intensity.
Used in Electronics and Optical Components:
Gadolinium is used in the creation of phosphors used in television tubes and the creation of gadolinium yttrium garnets (Gd:Y3Al5O12) used in microwaves. Gadolinium compounds are also used for making green phosphors for color TV tubes.
Used in Alloys:
Gadolinium 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.
Used in Nuclear Power:
Gadolinium oxide (Gd2O3) is used in the control rods of some nuclear reactors as a nuclear control rod material. It is also used for neutron shielding, phosphor activator, catalyst, and scavenger for oxygen in titanium production.
Used in Microwave Applications:
Gadolinium is used in the manufacture of Gadolinium Yttrium Garnet (Gd:Y3Al5O12), which has microwave applications and is used in the fabrication of various optical components and as substrate material for magneto-optical films.
Used in Superconductive Materials and Magnetic Refrigeration:
Gadolinium metal is widely used for making specialty alloys, MRI, superconductive materials, and magnetic refrigerator.
Used in Nuclear Marine Propulsion Systems:
Gadolinium is used as a burnable poison in nuclear marine propulsion systems.
Used in X-ray Systems:
In X-ray systems, gadolinium is contained in the phosphor layer, suspended in a polymer matrix at the detector.
Used in Catalysts and Scavengers:
Gadolinium is used as a catalyst to speed up chemical reactions and as a scavenger for oxygen in titanium production.
Used in High-Temperature Furnaces:
Gadolinium is used in high-temperature furnaces due to its ability to withstand low temperatures.
Used in Neutron Shielding and Absorption:
Gadolinium's main use is based on its ability to absorb neutrons, making it ideal as a neutron-shielding and neutron-absorbing metal.
Used in Alloying Agent for Steel and Other Metals:
Gadolinium is used as an alloying agent for steel and other metals to make them more workable and able to withstand low temperatures.
Used in Garnets in Microwave Filters:
Gadolinium is used in the manufacture of garnets used in microwave filters.
Physical Properties:
Gadolinium is silvery-white, soft, malleable, and ductile with a metallic luster. It tarnishes in air, forming the oxide (Gd2O3) on the surface, which flakes off the surface, exposing a fresh metal that in turn oxidizes.
Occurrence:
Gadolinium is found in monazite river sand in India and Brazil, the beach sand of Florida, and in bastnasite ores in southern California. It is also produced by nuclear fission in atomic reactors designed to produce electricity.
Chemical Properties:
Gadolinium is available as metal foil, chunks, or powder. The powder of gadolinium is highly flammable and is incompatible with strong oxidizing agents, halogens, and acids. It reacts with water or moisture.
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.
Isotopes
There are 39 isotopes of gadolinium. Seven of these are stable. They are: Gd-54, which makes up 2.18% of all the gadolinium found in the Earth’s crust; Gd-55,supplying 14.80%; Gd-156, making up 20.47%; Gd-157, constituting 15.56%; and Gd-158, accounting for 24.85%. In addition, there are two isotopes of gadolinium that areradioactive and with such long half-lives that they still exist in the Earth’s crust. They areregarded as stable isotopes along with the other seven. They are Gd-152 (1.08×10+14years), which exists in just 0.20% in abundance, and Gd-160 (1.3×10+21 years), foundin 21.86% abundance.
Origin of Name
Named for the mineral gadolinite, which was named for the French
chemist Johann Gadolin.
Characteristics
Gadolinium, unlike most of the rare earths in the dysprosium subgroup, reacts slowlywith water, releasing hydrogen. It is strongly magnetic at low temperatures. Two of its stableisotopes (Gd-155 and Gd-157) have the greatest ability of all natural elements to absorb thermalneutrons to control the fission chain reaction in nuclear reactors. However, few of theseisotopes are found in the ores of gadolinium.
History
Gadolinia, the oxide of gadolinium, was separated by Marignac in 1880 and Lecoq de Boisbaudran independently isolated Gadolinium from Mosander’s “yttria” in 1886. The element was named for the mineral gadolinite from which this rare earth was originally obtained. Gadolinium is found in several other minerals, including monazite and bastnasite, which are of commercial importance. 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. Thirtyone isotopes and isomers of gadolinium are now recognized; seven are stable and occur naturally. 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 α form. Upon heating to 1235°C, α gadolinium transforms into the β 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 loosely adhering oxide film which splits 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). 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. 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 Curie temperature (above which ferromagnetism vanishes) lying just at room temperature. This suggests uses as a magnetic component that senses hot and cold. The price of the metal is about $5/g (99.9% purity).
Hazard
The halogens of gadolinium are very toxic, and gadolinium nitrate is explosive. As withmost rare-earths, care should be taken not to inhale fumes or ingest particles of gadolinium.
Flammability and Explosibility
Flammable
Check Digit Verification of cas no
The CAS Registry Mumber 7440-54-2 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 7,4,4 and 0 respectively; the second part has 2 digits, 5 and 4 respectively.
Calculate Digit Verification of CAS Registry Number 7440-54:
(6*7)+(5*4)+(4*4)+(3*0)+(2*5)+(1*4)=92
92 % 10 = 2
So 7440-54-2 is a valid CAS Registry Number.
InChI:InChI=1/Gd
