Yttrium oxide

Yttrium oxide, Y₂O₃, is a white powder and one of the most heat-resistant oxides, melting at about 2,400 °C. It's the form yttrium is usually sold in, and where most uses of the element begin.

Yttrium is grouped with the rare earth elements and mined from the same ores, especially certain clays in southern China and minerals such as xenotime. The rare earths are so alike chemically that separating them takes hundreds of stages of solvent extraction, each nudging the balance slightly. The purified yttrium is precipitated from solution as an oxalate, then heated in air so it combines with oxygen and leaves the oxide. Phosphor makers often need 99.99% purity or better.

In this build it goes into YAG phosphor, where it joins aluminum oxide to form the garnet crystal. Yttrium oxide was also the base of the red phosphor in old tube TVs, where europium gave off the red. It's used in heat-resistant coatings and to stabilize zirconia ceramics. Yttrium, ytterbium, terbium and erbium are all named after Ytterby, a village in Sweden where their ore was found.