Yttrium (chemical symbol—Y) is a chemical element with the atomic number 39 of group 3 of the periodic table. Yttrium is a silvery-white, moderately soft ductile, highly crystalline, rare-earth metal. The only naturally occurring isotope of yttrium is the stable isotope Y-89. In total, 33 (excluding nuclear isomers) radioactive isotopes of yttrium ranging in mass from 77 to 109 and half-life from 41 milliseconds (yttrium-108) to 106.63 days (yttrium-88) have been discovered.
Yttrium doesn't occur naturally as a free element. It is found in almost all rare earth minerals (such as laterite clays, gadolinite, euxenite, and xenotime) and in uranium ores. The yellow-brown ore xenotime can contain as much as 50% yttrium phosphate (YPO4). Yttrium is also found in the rare-earth mineral monazite (making up 2.5%) and in smaller quantities in other minerals such as barnesite, fergusonite, and samarskite. In the igneous rocks of Earth’s crust, yttrium is more plentiful than any of the other rare-earth elements, except cerium, and is twice as abundant as lead. Yttrium also occurs in products of nuclear fission. Yttrium exists in two allotropic (structural) forms. The α-phase is close-packed hexagonal with a = 3.6482 Å and c = 5.7318 Å at room temperature. The β-phase is body-centred cubic with a = 4.10 Å at 1,478 °C (2,692 °F).
The top three producers of yttrium are China, Russia, and Malaysia. The output of yttrium is roughly 600 tonnes per year, measured as yttrium oxide, and global reserves are estimated to be around 9 million tonnes.
Yttrium is relatively stable in air due to being protected by the formation by the formation of a stable oxide film on its surface. It oxidizes readily when heated, at around 840oF (450oC), producing Y2O3. It reacts with water decomposing and releasing hydrogen gas, and it reacts with mineral acids. Shavings or turnings of the metal can ignite in air when they exceed 400 °C. When yttrium is finely divided, it is very unstable in air. Yttrium behaves chemically as a typical rare-earth element, having an oxidation state of +3. Its ionic radius is near the radii of dysprosium and holmium, making separation from those elements difficult. Besides the white sesquioxide, yttrium forms a series of nearly white salts, including the sulfate, the trichloride, and the carbonate.
A table of yttrium facts and properties is shown below:
Yttrium facts and properties
3345oC, 6053oF, 3618K
In 1787, Swedish amateur geologist and chemist Karl Arrhenius came across an unusual black rock in an old quarry at Ytterby, near Stockholm. Thinking he had found a new tungsten mineral, Arrhenius passed the specimen over to Johan Gadolin, based in Finland. In 1794, Gadolin announced that it contained a new "earth," which made up 38 percent of its weight. Gadolin called the discovery an "earth" because it was yttrium oxide (Y2O3), which could not be reduced further by heating with charcoal.Over a span of more than a century, nine elements, including yttrium, scandium (atomic number 21), and the heavy lanthanide metals from terbium (atomic number 65) to lutetium (atomic number 71), were separated from the new "earth" or metallic oxide named yttria.
The metal itself was first isolated in 1828 by Friedrich Wöhler. Wöhler reacted yttrium chloride with potassium. In 1843, Carl Mosander investigated yttrium oxide more thoroughly and found that it consisted of three oxides: yttrium oxide, which was white; terbium oxide, which was yellow; and erbium oxide, which was rose-colored. Yttrium is named after Ytterby, Sweden.
For commercial purposes, yttrium is separated from other rare earths by liquid-liquid or ion-exchange extraction, and the metal is produced by metallothermic reduction of the anhydrous fluoride with calcium. Yttrium and its compounds have many uses:
- The largest use of the element is as its oxide yttria (Y2O3) as hosts for red phosphors for fluorescent lamps, color displays, and TV screens that use cathode-ray tubes
- Yttrium aluminum garnet (YAG) doped with other rare earths is used in lasers
- Yttrium iron garnet (YIG) is used for microwave filters, radars, communications, and synthetic gems
- Yttrium oxide-stabilized cubic zirconia is used in oxygen sensors, structural ceramics, thermal barrier coatings, and synthetic diamonds
Yttrium metal has also found some use alloyed in small amounts with other metals to increase strength; examples include aluminum and magnesium alloys. When added to cast iron, yttrium can make the metal more workable. Although metals are generally good at conducting heat, there is an alloy of yttrium with chromium and aluminum, which is heat resistant. Yttrium oxide in glass makes it heat- and shock-resistant and is used for camera lenses. Yttrium oxide is suitable for making superconductors, which are metal oxides that conduct electricity without any loss of energy.