We continue to review some of the most important materials in heat treatment and metallurgy.

Yttrium (chemical symbol: Y)

Yttrium, a rare-earth element, is a soft, silvery metal with a number of high-tech applications. In the heat-treat industry, yttrium is often used as an alloying element to increase the strength of aluminum and magnesium alloys and to produce other useful alloys.  

Yttrium was discovered in 1794 by Finnish chemist, physicist and mineralogist Johan Gadolin. Considered the founder of Finnish chemistry research, Gadolin was a brilliant researcher who was fluent in Latin, Finnish, Russian, German, English and French, in addition to his native Swedish. Yttrium was named after the village of Ytterby in Sweden. A famous quarry in Ytterby is the source of 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.

Yttrium is used in concentrations of 0.1-0.2% as an alloying agent in chromium, molybdenum, zirconium and titanium to reduce the grain size. It is used as a deoxidizer for vanadium and other nonferrous metals. Yttrium 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, which results in increased ductility of the iron.5

The most common use of yttrium oxide is in the making of europium phosphors, which provide the red color in cathode-ray tubes. Hundreds of thousands of pounds are used for this purpose. Another main use for yttrium oxide is to produce yttrium-iron garnets (Fig. 1), which are very effective microwave filters. Garnets are a class of silicate materials with unique properties that have been used as gemstones and abrasives for thousands of years. In recent years, yttrium-iron garnets have been used as acoustic transmitters and transducers since they are extremely efficient transmitters and transducers of acoustic energy. They also find use in solid-state lasers, Faraday rotators, data storage and for certain nonlinear optics applications. Yttrium-aluminum garnets are used as gemstones, simulating natural diamond, and to form laser components.

Here are a few scientific and engineering facts about yttrium.1

  • Atomic number: 39
  • Atomic weight: 88.90584
  • Melting point: 1795 K (1522°C or 2772°F)
  • Boiling point: 3618 K (3345°C or 6053°F)
  • Density: 4.47 grams per cubic centimeter
  • Phase at room temperature: Solid
  • Element classification: Metal



1. Jefferson Lab (https://www.jlab.org)