Sep 12 2002
Yttria (Y), an earth containing yttrium was discovered in 1794 by Gadolin. It was found in a quarry located at Ytterby in Sweden. This site yielded several unusual minerals containing rare earths and other elements. The town is responsible for the names erbium, terbium and ytterbium.
Mosander showed that yttria contained the earths of three elements in 1843. The names yttria was given to the most basic, while the other two became erbia and terbia.
Impure samples of yttrium were prepared by Wohler in 1828 who reduced the anhydrous chloride with potassium.
Yttrium can be found in nearly all rare earth minerals. It was also identified in lunar rocks brought back by Apollo missions, which were found to have quite high yttrium contents.
Occurrence and Production
Commercially yttrium is refined from monazite and bastnasite sands which contain approximately 3% ands 0.2% respectively. Yttrium metal is commercially produced by the reduction of the fluoride with calcium metal, although other techniques also exist.
• It has a silvery metallic lustre
• It is relatively stable in air if the above 400°C
• Finely divided yttrium is highly unstable in air
• Turnings of yttrium are prone to ignition in air
• Has a low cross section for nuclear capture
Yttrium metal is used as:
• A deoxidiser for vanadium and other non-ferrous metals
• Potentially as a noduliser for nodular cast iron
• A catalyst for ethylene polymerisation
• It is also added in small quantities (0.1 to 0.2%) to reduce the grain size in chromium, molybdenum, zirconium and titanium, as well as to strengthen aluminium and magnesium alloys.
Yttrium compounds have the following uses:
• Yttrium oxide is used to produce yttrium iron garnets which are useful microwave filters
• Yttrium oxide is used in ceramic and glass formulations as it has a high melting point and imparts thermal shock resistance and low expansion characteristics to glass
• Yttrium oxide is widely used for making compounds such as YVO4europium and YVO4europium phosphors which are responsible for the red colour in television tubes.
• Yttrium iron (Y3Fe5O12), yttrium aluminium (Y3Al5O12) and yttrium gadolinium garnets possess interesting magnetic properties
• Yttrium iron garnets are extremely efficient transmitters and transducers of acoustic energy
• Yttrium aluminium garnet has a hardness of 8.5 and is finding application as a gemstone (synthetic diamond)