Yttrium (Y), the element with atomic number 39, is unequivocally classified as a metal. This silvery-white, crystalline element is never found in its pure form in nature, always occurring in compounds with other elements.
Where Yttrium Sits on the Periodic Table
Yttrium holds a specific place as a transition metal, located in Group 3 and Period 5 of the periodic table. This placement in the d-block technically groups it with elements like Scandium and Lanthanum. Its chemistry, however, is almost identical to that of the Lanthanide series, which are the 15 elements with atomic numbers 57 through 71.
The reason for this chemical alignment is that the size of the yttrium ion (\(Y^{3+}\)) closely matches the size of the heavier lanthanide ions, particularly those of dysprosium and holmium. Because of this strong chemical similarity, yttrium is invariably found in the same mineral deposits as the lanthanides. This is why yttrium is universally and commercially classified alongside the Lanthanides as one of the “Rare Earth Elements,” even though it is not technically a lanthanide itself.
Key Characteristics of Yttrium Metal
As a metal, yttrium exhibits high thermal and electrical conductivity. It also possesses a notably high melting point, averaging around \(1,522 \ \text{°C}\) (\(2,772 \ \text{°F}\)), which makes it valuable in high-temperature industrial processes. Despite its high melting point, yttrium has a relatively low density of approximately \(4.47 \ \text{g/cm}^3\), distinguishing it from many other heavy transition metals.
Yttrium is a chemically reactive metal, a trait that is controlled by its surface interaction with air. In its bulk form, the metal quickly forms a thin, protective layer of yttrium oxide (\(\text{Y}_2\text{O}_3\)) on its surface, which prevents further oxidation at room temperature. However, when heated above \(450 \ \text{°C}\) (\(840 \ \text{°F}\)), the oxidation accelerates rapidly, and the metal can ignite and burn white-hot if it is in a powdered or finely divided state. It also readily reacts with most diluted acids, although hydrofluoric acid is an exception, as it forms an insoluble protective fluoride layer.
Common Uses of Yttrium Today
Yttrium compounds are widely used in the production of phosphors, which are materials that emit light when energized. Specifically, yttrium oxide doped with europium is responsible for the vivid red color in older cathode ray tube (CRT) television screens and remains a component in modern LED lighting and displays.
Yttrium is also frequently incorporated into specialized ceramics, such as Yttria-Stabilized Zirconia (YSZ). This ceramic material is used in oxygen sensors for automobiles and as a highly durable thermal barrier coating to protect components in jet engines from extreme heat. Furthermore, the metal is a component in Yttrium Aluminum Garnet (YAG) crystals, which are manufactured for use in high-power lasers for industrial cutting and welding, as well as for precise medical procedures.
Another important use is its inclusion in high-temperature superconducting materials, such as the ceramic Yttrium Barium Copper Oxide (\(\text{YBa}_2\text{Cu}_3\text{O}_7\)), commonly known as YBCO. When added to metal alloys, such as those based on aluminum or magnesium, small amounts of yttrium significantly increase the alloy’s strength and resistance to corrosion and oxidation, making these materials suitable for high-performance aerospace components.