CODEX Entry 8118: Gadolinium
Gadolinium is a silvery-white rare-earth metal. The metal is too reactive to exist naturally. The main mining areas are in China, the US, Brazil, Sri Lanka, India, and Australia. World production is about 400 tonnes per year. The metal is a helical antiferromagnetic below 20 °C and above 20 °C, it is the most paramagnetic element. As little as 1% of gadolinium can significantly improve the workability and resistance to oxidation of iron, chromium, and related metals. Gadolinium-157 has the highest non-radioactive thermal-neutron capture and can be visualized with an electron microscope. Therefore it is used for shielding in neutron radiography, to target tumors in neutron therapy, and intravenously as an MRI contrast agent. Once injected, gadolinium-based contrast agents accumulate in abnormal tissues of the brain and body, which provides a greater image contrast between normal and abnormal tissues, facilitating location of abnormal cell growths and tumors. Gadolinium as a phosphor is also used in other imaging. It converts 1/5th of the X-rays released from the source into light making it useful for measurements in bone density. It can also be incorporated into carbon nanotubes, called “gadonanotubes”, which are 40 times more effective. In nuclear reactors it is used as an emergency shut-down measure, and also in nuclear marine propulsion systems as a burnable poison. It has microwave applications and is used in fabrication of various optical components, magneto-optical films, and computer bubble memory. Gadolinium can also serve as an electrolyte in solid oxide fuel cells (SOFCs). Physicists Mark Vagins and John Beacom, of the Japanese Super Kamiokande, theorized that gadolinium may facilitate neutrino detection when it is added to very high-purity water in the tank and in hypothetical papers on future viability of warp drives. Gadolinium barium copper oxide (GdBCO) has been researched for superconducting motors or generators. It set a new world record for the highest trapped magnetic field in a bulk high temperature superconductor.