The existence of gallium was predicted in 1871 by Mendeleev, who called it eka-aluminium. In 1875 Lecoq de Boisbaudran, whose curiosity had been aroused by the presence of unknown lines in the spectrum of a zinc mineral originating from the Pyrenees, succeeded in isolating the metal, which he named gallium after his native France (Gallia). Gallium remained a laboratory curiosity until 1970 when the semiconductor properties of some of its compounds were discovered.
- A silvery white metal that melts at 29.76°C and boils at 2204°C; it is thus liquid over a temperature range of some 2000°C, with a vapour pressure that remains low at least up to 1500°C.
- On cooling, the metal can remain liquid below its melting point (superfusion), down to 0°C.
- Its volumic mass is higher in the liquid than in the solid state, which means that the metal expands on solidifying (by 3.2%).
- Diffuses rapidly through the crystal lattice of certain metals, e.g. aluminium, causing them to become brittle.
- Metallic gallium is magnetic and an excellent conductor of both heat and electricity
Gallium arsenide and gallium nitride single crystals are used in the manufacture of photovoltaic cells and LEDs.
In space solar cell applications, GaAs epitaxial films deposited on germanium substrates are used; the higher mechanical strength of germanium allowing thinner, and hence lighter, wafers to be manufactured.
Gallium arsenide is also used in mobile telephones and certain microwave appliances, enabling higher-frequency operation and lower energy usage than can be achieved with silicon-based devices.
End-of-life recycling is challenging due to the dissipative use of gallium. Most of the recovered gallium comes from the production residues of gallium used in the epitaxy process for making semiconductors.