Gadolinium

 

Notable characteristics

Gadolinium is a silvery-white, malleable and K or more, it transforms into its beta form, which has a body-centered cubic structure.

Unlike other rare earth elements, gadolinium is relatively stable in dry air. However, it tarnishes quickly in moist air and forms a loosely-adhering oxide that spalls off, and then exposes more surface to oxidation. Gadolinium reacts slowly with water, and it is soluble in dilute acids.

Gadolinium-157 has the highest thermal neutron Xenon-135, 49,000 barns, but it also has a fast burn-out rate, limiting its usefulness as a nuclear control rod material.

Gadolinium becomes ferromagnetic properties below room temperature.

Gadolinium demonstrates a magnetocaloric effect whereby its temperature increases when it enters a magnetic field and decreases when it leaves the magnetic field. The effect is considerably stronger for the gadolinium Ge₂) ^[1].

Applications

Gadolinium is used for making gadolinium yttrium garnets, which have phosphors for colour TV tubes. Gadolinium is also used for manufacturing compact discs and computer memory.

Gadolinium is used in nuclear marine propulsion systems as a burnable poison. The gadolinium slows the initial reaction rate, but, as it decays, other neutron poisons accumulate, allowing for long-running cores. Gadolinium is also used as a secondary, emergency shut-down measure in some nuclear reactors, particularly of the CANDU type.

Gadolinium also possesses unusual oxidation.

Because of their intravenous radiocontrast agents to enhance images in medical magnetic resonance imaging. Magnevist is the most widespread example.

Besides MRI, gadolinium (Gd) is also used in other imaging. In photoelectric interactions is great. The energy conversion of Gd is up to 20%, which means, one-fifth of the X-ray striking on the phosphor layer can be converted into light photons.

Gadolinium oxyorthosilicate (Gd₂SiO₅, GSO; usually doped by 0.1-1% of Positron Emission Tomography (PET), and for detecting neutrons.

Gadolinium gallium garnet (Gd₃Ga₅O₁₂) is a material with good optical properties, and is used in fabrication of various optical components and as substrate material for magneto–optical films.

In the future, gadolinium ethyl sulfate, which has extremely low noise characteristics, may be used in Curie temperature (which lies just at room temperature) suggest applications as a magnetic component for sensing hot and cold.

Due to extremely high neutron cross-section of gadolinium, this element is very effective for use with neutron radiography.

History

In 1880, Swiss oxide of Gadolinium, from Mosander's yttria in 1886. The element itself was isolated only recently.

Gadolinium, like the mineral Johan Gadolin.

In older literature, the natural form of the element is often called an earth, meaning that the element came from Earth. In fact, gadolinium is the element that comes from the earth, gadolinia. Earths are compounds of the element and one or more other elements. The two most common combining-elements are oxygen and sulfur. For example, gadolinia contains gadolinium oxide (Gd₂O₃).

Biological role

Gadolinium has no known native biological role, but in research on biological systems it has a few roles. It is used as a component of MRI contrast agents, as, in the 3+ oxidation state, the metal has 7 unpaired f electrons. This causes water around the contrast agent to relax quickly, enhancing the quality of the MRI scan. Second, as a member of the lanthanides, it is used in various Ion Channel electrophysiology experiments, where it is used to block sodium leak channels, as well as to stretch activated ion channels.

Occurrence

Gadolinium is never found in nature as the free element, but is contained in many rare minerals such as calcium.

Value

In 1994, the cost of gadolinium was about US$ 0.12 per gram, and it has only increased in value by about US$ 0.01 per gram since then.^[2]:

1994.....$55 per pound (or $0.121 per gram)

1995.....$55 per pound (or $0.121 per gram)

1996.....$115 per kilogram (or $0.115 per gram)

1997.....$115 per kilogram (or $0.115 per gram)

1998.....$115 per kilogram (or $0.115 per gram)

1999.....$115 per kilogram (or $0.115 per gram)

2000.....$130 per kilogram (or $0.13 per gram)

2001.....$130 per kilogram (or $0.13 per gram)

2002.....$130 per kilogram (or $0.13 per gram)

2003.....$130 per kilogram (or $0.13 per gram)

2004.....$130 per kilogram (or $0.13 per gram)

2005.....$130 per kilogram (or $0.13 per gram)

Compounds

Compounds of gadolinium include:

• Fluorides: GdF₃
• GdCl₃
• Bromides: GdBr₃
• Iodides: GdI₃
• Oxides: Gd₂O₃
• Sulfides: Gd₂S₃
• Nitrides: GdN
• gadodiamide

See also gadolinium compounds.

Isotopes

Main article: Isotopes of gadolinium

Naturally-occurring gadolinium is composed of 5 stable radioisotopes, ¹⁵²Gd and ¹⁶⁰Gd, with ¹⁵⁸Gd being the most abundant (24.84% natural abundance).

Thirty radioisotopes have been characterized, with the most stable being ¹⁶⁰Gd with a half-life of more than 1.3×10²¹ years (the decay has not been observed - only the lower limit on the half-life is known), alpha-decaying ¹⁵²Gd with a half-life of 1.08×10¹⁴ years, and ¹⁵⁰Gd with a half-life of 1.79×10⁶ years. All of the remaining isotopes are radioactive, having half-lives less than 74.7 years. The majority of these have half-lives less than 24.6 seconds. Gadolinium isotopes have 4 metastable isomers, with the most stable being ^143mGd (t_½ 110 seconds), ^145mGd (t_½ 85 seconds) and ^141mGd (t_½ 24.5 seconds).

The primary terbium) isotopes.

Gadolinium-153 has a half-life of 240.4 ±10 days and emits gamma radiation with strong peaks at 41keV and 102keV. It is used as a gamma ray source in x-ray absorptiometry or bone density gauges for osteoporosis screening, and in the Lixiscope portable x-ray imaging system.

Precautions

As with the other lanthanides, gadolinium compounds are of low to moderate toxicity, although their toxicity has not been investigated in detail. Also, in patients on dialysis, there are data suggesting that it may cause nephrogenic fibrosing dermopathy^[3] as a side effect of MRI investigations that require the use of a Gadolinium based contrast agent.

References

1. ^ Karl Gschneidner, Jr. and Kerry Gibson (December 7, 2001). MAGNETIC REFRIGERATOR SUCCESSFULLY TESTED. Ames Laboratory News Release. Ames Laboratory. Retrieved on 2006-12-17.
2. ^ James B. Hedrick (1994). "Rare Earths". USGS Commodity Statistics and Information: 72. [1].
3. ^ Grobner T. (2006-01-23). "Gadolinium — a specific trigger for the development of nephrogenic fibrosing dermopathy and nephrogenic systemic fibrosis?". Nephrology Dialysis Transplantation 21 (4): 1104-8.

General references

• Los Alamos National Laboratory – Gadolinium