Yttrium is a silver-metallic, lustrous rare earth metal that is relatively stable in air and chemically resembles the lanthanides. 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.
- Yttrium oxide is used to make yttrium iron garnets which are very effective microwave filters.
- Yttrium iron, aluminium, 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 aluminium 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 aluminium and magnesium alloys.
- Used as a catalyst for ethylene polymerization.
- Yttrium aluminium garnet, yttrium lithium fluoride, and yttrium vanadate are used in combination with dopants such as neodymium or erbium in infrared lasers.
- 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 aluminium garnet (YAG:Ce) crystals are used as phosphors to make white LEDs.
Yttrium is found on many planets, but is most abundant on Yttric worlds.