Appearance and Characteristics
Harmful effects:
Water soluble compounds of yttrium are considered to be slightly toxic, while its insoluble compounds are considered to be non-toxic.
Characteristics:
Yttrium is a soft, silvery metal. Yttrium usually exists as a trivalent ion, Y3+, in its compounds. Most of its compounds are colorless.
Yttrium’s properties are very similar to those of the rare earth elements of the lanthanide series. Accordingly, yttrium is classified as one of the rare earth elements.
It is relatively stable in air as a result of an oxide film which forms on its surface.
The finely divided metal ignites in air when heated.
Yttrium reacts with water to form yttrium hydroxide plus hydrogen gas.
Interestingly, samples of rock and dust brought back from the Apollo moon landings show a high yttrium content. The yttrium content in lunar soil samples ranged from 54 to 213 parts per million. This compares with an average abundance of 33 parts per million in the earth’s crust.
Yttrium has an exceptionally high affinity for oxygen, with a free energy of formation for the oxide of 1817 kJ mol-1, probably the greatest of any element. Yttrium also dissolves oxygen gas in relatively high concentrations.
Uses of Yttrium
Yttrium is often used in alloys, increasing the strength of aluminum and magnesium alloys.
It is also used as a deoxidizer for non-ferrous metals such as vanadium.
Yttrium is used as a catalyst in ethylene polymerization.
Yttrium-90, a radioactive isotope, is used in treatments for various cancers and is used in precision medical needles to sever pain-transmitting nerves in the spinal cord.
Yttrium oxide is the most important compound of yttrium. It is used to make the high-temperature superconductor YBCO (yttrium barium copper oxide). This substance becomes superconducting at -178 oC (meaning that it can be kept in a superconducting state using liquid nitrogen, rather than more expensive and more difficult to handle liquid helium).
Yttrium oxide is also used to make yttrium iron garnets (Y3 Fe5O12) which are very effective microwave filters, blocking some microwave frequencies, while allowing others through in communication devices such as satellites.
Yttrium doped with europium is used to produce phosphors, which provide the red color in color television tubes.