Y - Yttrium

Properties

Yttrium is a soft, silvery-white metal that is a member of Group 3 of the Periodic Table; it is the 28th most abundant element within the Earth’s crust. Yttrium is stable in air, as it is protected by the formation of a resistant oxide film on its surface. It burns if ignited, and is attacked by water, which decomposes it to release hydrogen gas. Yttrium, when cut small enough, will burn spontaneously in air. Surprisingly, rocks brought back from the moon by the Apollo astronauts contained an unusually high yttrium content.

History

Yttrium was first discovered in 1787 in Sweden in a small village called Ytterby, from which its name is derived. Several other elements: ytterbium, erbium and terbium were also found in quarries in this town, as the choice of names show. Yttrium was discovered in its oxide form by an army Lieutenant, Karl Axel Arrhenius, who came across a coal-like substance. Whilst analysing this object, he realised that it was definitely too heavy to be a lump of coal. He then passed the mineral on to a chemist, Johan Gadolin, of the University of Abo, Finland. It was Gadolin who investigated this mineral and determined that there was a new ‘earth’ responsible for 38% of the weight of the black rock. It was Gadolin who gave yttrium its name, but he was unable to isolate the metal, and it was not until 1828 that this was acheived by Freidrich Woller.

Sources

Yttrium phosphate makes up approximately 50% of the ore Xenotime.  Yttrium oxide though, is mainly found in a rare earth mineral Monazite and makes up about 2.5% of it.  Other minerals containing yttrium oxide in smaller quantities are fergusonite and samarskite.

Yttrium oxide is extracted from the aforementioned ores, of which about 600 mt are produced a year.  There are thought to be world reserves of yttrium oxide in the region of 9,000,000mt, while comparatively there are only a few tonnes of yttrium metal produced each year, which requires yttrium fluoride to be heated with calcium metal in order to be produced.

Uses

Yttrium is used in alloys which improve magnesium (Mg) castings.  It gives a finer grain to chromium (Cr), molybdenum (Mo) and zirconium (Zr) metals.  Also, when added to cast iron, it makes it more workable.  Unusually for metals, when alloyed with chromium and aluminium it becomes heat resistant.  Yttrium oxysulfide, when doped with europium, creates the red colour in televisions.  Yttrium oxide is used as a glass additive, rendering it heat and shock resistant, and is therefore used in camera lenses.  Yttrium oxide is also used for making superconductors, and the compound yttrium-barium-copper oxide (YB2Cu3O7-9) was the first superconductor to work at temperatures of liquid nitrogen (-183°C).  Yttrium-iron-garnet (YIG) is used as resonators in frequency meters and in magnetic recording.   Yttrium also has an important role within aerospace where it is used as a stabiliser and mold-former for jet engine turbines among other parts.