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History

Yttrium (named for Ytterby, a Swedish village near Vaxholm) was discovered by Finnish chemist, physicist, and mineralogist Johan Gadolin in 1794 and isolated by Friedrich Wohler in 1828 as an impure extract of yttria through the reduction of yttrium anhydrous chloride (YCl₃) with potassium.  Yttria (Y₂O₃) is the oxide of yttrium and was discovered by Johan Gadolin in 1794 in a gadolinite mineral from Ytterby.

In 1843, the great Swedish chemist Carl Mosander was able to show that yttria could be divided into the oxides (or earths) of three different elements. "Yttria" was the name used for the most basic one and the others were re-named erbia and terbia.

A quarry is located near the village of Ytterby that yielded many unusual minerals that contained rare earth and other elements. The elements erbium, terbium, ytterbium and and yttrium have all been named after this same small village.

Characteristics

Yttrium is a silver-metallic, lustrous rare earth metal that is relatively stable in air, strongly resembles scandium in appearance, and chemically resembles the lanthanides, and can appear to gain a slight pink lustre on exposure to light.  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. The metal has a low neutron cross-section for nuclear capture.  The common oxidation state of yttrium is +3.  The current claim-to-fame for yttrium is its use in the so-called 1-2-3 oxide superconductors (along with barium and copper). These were the first superconducting materials to function at liquid nitrogen temperatures.

Occurrence

This element is found in almost all rare-earth minerals and in uranium ores but is never found in nature as a free element. Yttrium is commercially recovered from monazite sand (3% content, (Ce, La, etc.)PO₄) and from bastnasite (0.2% content, (Ce, La, etc.)(CO₃)F). It is commercially produced by reducing yttrium fluoride with calcium metal but it can also be produced using other techniques. It is difficult to separate from other rare earths and when extracted, is a dark gray powder.

Lunar Rock samples from the Apollo program have a relatively high yttrium content.

Applications

Yttrium (III) oxide is the most important yttrium compound and is widely used to make YVO₄:Eu and Y₂O₃:Eu phosphors that give the red color in color television picture tubes. Other uses include:

• Yttrium oxide is also used to make yttrium iron garnets which are very effective microwave filters. 
• Yttrium iron, aluminum, and gadolinium garnets (e.g. Y₃Fe₅O₁₂ and Y₃Al₅O₁₂) have interesting magnetic properties.   Yttrium iron garnet is very efficient as an acoustic energy transmitter and transducer.  Yttrium aluminum garnet has a hardness of 8.5 and is also used as a gemstone (simulated diamond).
• Small amounts of the element (0.1 to 0.2%) have been used to reduce grain size of chromium, molybdenum, titanium, and zirconium.  It is also used to increase the strength of aluminum and magnesium alloys.
• Used as a catalyst for ethylene polymerization.
• Yttrium aluminum garnet, yttrium lithium fluoride, and yttrium vanadate are used in combination with dopants such as neodymiun or erbium in infrared lasers.
• It is used on the electrodes of some high-performance spark plugs.
• This metal can be used to deoxidize vanadium and other nonferrous metals.
• Yttrium is also used in the manufacture of gas mantles for propane lanterns, as a replacement for thorium, which is slightly radioactive.
• Cerium-doped yttrium aluminum garnet (YAG:Ce) crystals are used as phosphors to make white LEDs. 
• Yttrium-90 microspheres have shown promise as a treatment for hepatocelluar carcinoma.
• Yttrium was used as a "secret" element in a superconductor developed at the University of Houston, YBaCuO.  This superconductor operated above 90K, an amazing feat because it can operate at above liquid nitrogen's boiling point. (Y_1.2Ba_0.8CuO₄). The matter created was a multi-crystal multi-phase mineral, which was black and green.

Yttrium has been studied for possible use as a nodulizer in the making of nodular cast iron which has increased ductility (the graphite forms compact nodules instead of flakes to form nodular cast iron).  Potentially, yttrium can be used in ceramic and glass formulas, since yttrium oxide has a high melting point and imparts shock resistance and low thermal expansion characteristics to glass.

Compounds

Although metallic yttrium is not widely used, several of its compounds are. Yttrium oxide (Y₂O₃) and yttrium orthovanadate (YVO₄) are both combined with europium to produce the red phosphor used in color televisions. Garnets made from yttrium and iron (Y₃Fe₅O₁₂) are used as microwave filters in microwave communications equipment. Garnets made from yttrium and aluminum (Y₃Al₅O₁₂) are used in jewelry as simulated diamond.

Isotopes

Natural yttrium is composed of only one stable isotope (Y-89).  The most stable radioisotopes are Y-88 which has a half-life of 106.65 days and Y-91 with a half life of 58.51 days. All the other isotopes have half lifes of less than a day except Y-87 which has a half life of 79.8 hours.  The dominant decay mode below the stable Y-89 is electron capture and the dominant mode after it is beta emission.  Twenty six unstable isotopes have been characterized.

Y-90 exists in equilibrium with its parent isotope strontium-90, which is a product of nuclear explosions.

Precautions

Compounds that contain this element are rarely encountered by most people but should be considered to be highly toxic even though many compounds pose little risk.   Yttrium salts may be carcinogenic.

This element is not normally found in human tissue and plays no known biological role.

Yttrium metal is ductile and silvery. Powdered samples and turnings from machining can burst into flame.

(Ytterby, a village in Sweden near Vauxholm) Yttria, which is an earth containing yttrium, was discovered by Gadolin in 1794. Ytterby is the site of a quarry which yielded many unusual minerals containing rare earths and other elements. This small town, near Stockholm, bears the honor of giving names to erbium, terbium, and ytterbium as well as yttrium. In 1843 Mosander showed that yttira could be resolved into the oxides (or earths) of three elements. The name yttria was reserved for the most basic one; the others were named erbia and terbia. Yttrium occurs in nearly all of the rare-earth minerals. Analysis of lunar rock samples obtained during the Apollo missions show a relatively high yttrium content. It is recovered commercially from monazite sand, which contains about 3%, and from bastnasite, which contains about 0.2%. Wohler obtained the impure element in 1828 by reduction of the anhydrous chloride with potassium. The metal is now produced commercially by reduction of the fluoride with calcium metal. It can also be prepared by other techniques. Yttrium has a silver-metallic luster and is relatively stable in air. Turnings of the metal, however, ignite in air if their temperature exceeds 400^oC, and finely divided yttrium is very unstable in air. Yttrium oxide is one of the most important compounds of yttrium and accounts for the largest use. It is widely used in making YVO₄ europium, and Y₂O₃ europium phosphors to give the red color in color television tubes. Many hundreds of thousands of pounds are now used in this application. Yttrium oxide also is used to produce yttrium-iron-garnets, which are very effective microwave filters. Yttrium iron, aluminum, and gadolinium garnets, with formulas such as Y₃Fe₅O₁₂ and Y₃Al₅O₁₂, have interesting magnetic properties. Yttrium iron garnet is also exceptionally efficient as both a transmitter and transducer of acoustic energy. Yttrium aluminum garnet, with a hardness of 8.5, is also finding use as a gemstone (simulated diamond). Small amounts of yttrium (0.1 to 0.2%) can be used to reduce the grain size in chromium, molybdenum, zirconium, and titanium, and to increase strength of aluminum and magnesium alloys. Alloys with other useful properties can be obtained by using yttrium as an additive. The metal can be used as a deoxidizer for vanadium and other nonferrous metals. The metal has a low cross section for nuclear capture. 90Y, one of the isotopes of yttrium, exists in equilibrium with its parent 90Sr, a product of nuclear explosions. Yttrium has been considered for use as a nodulizer for producing nodular cast iron, in which the graphite forms compact nodules instead of the usual flakes. Such iron has increased ductility. Yttrium is also finding application in laser systems and as a catalyst for ethylene polymerization. It also has potential use in ceramic and glass formulas, as the oxide has a high melting point and imparts shock resistance and low expansion characteristics to glass. Natural yttrium contains but one isotope, 89Y. Nineteen other unstable isotopes have been characterized. Yttrium metal of 99.9% purity is commercially available at a cost of about $75/oz.

Source: CRC Handbook of Chemistry and Physics, 1913-1995. David R. Lide, Editor in Chief. Author: C.R. Hammond