What Is Gallium?
Gallium is a soft, odorless, silvery-white metal.
Gallium’s elemental symbol is Ga, its atomic number is 31, and its CAS number is 7440-55-3. Gallium is widely distributed in nature and is found in trace amounts in minerals such as bauxite and germanite, which are aluminum ores.
Uses of Gallium
Gallium is used as a semiconductor material because it is a compound semiconductor as gallium arsenide, a compound with arsenic. Gallium arsenide is used in electronic products such as laser printers, supercomputers, and cellular phones.
Gallium nitride (GaN), a compound of Gallium and nitrogen, is used in blue light-emitting diodes (LEDs). Blue LEDs are used in Blu-ray Discs, LED light bulbs, and new types of traffic lights.
Properties of Gallium
Gallium has a melting point of 29.8 °C and a boiling point of 2,403 °C. It exists as a solid or liquid at room temperature and has a density of 5.91 g/cm3 in the solid state. Among metals, Gallium’s best-known characteristic is its low melting point. It is antimagnetic in the solid state, but paramagnetic in the liquid state, with a magnetic susceptibility of 2.4 x 10−6 at 40 °C.
Structure of Gallium
Unlike other metals, Gallium does not crystallize in any of the simple crystal structures. The stable phases at ambient pressure are α-, β-, γ-, and δ-Gallium, which form under different conditions, and Ga-II, Ga-III, and Ga-IV, which form at high pressure.
1. Structure of Α-Gallium
α-Gallium is a polymorph of Gallium existing under normal conditions and has an orthorhombic structure with eight atoms in the unit lattice. The distance between the nearest atoms is 244 pm, and the six neighbors are separated by an additional 39 pm. This unstable, poorly symmetric structure is believed to be responsible for Gallium’s low melting point.
2. Other Polymorphs
Other crystalline forms of Gallium can be obtained by crystallization from supercooled liquid Gallium. Above -16.3 °C, monoclinic β-Gallium is formed with a zigzag structure of gallium atoms, and above -19.4 °C, triclinic δ-Gallium is formed with a distorted arrangement of 12 gallium atoms, a crystal structure similar to α-boron At -35.6 °C, δ-gallium is formed. At -35.6 °C, orthorhombic γ-Gallium is formed, which has a structure similar to that of α-boron, with seven gallium atoms arranged in a ring and a linear arrangement of atoms interconnected in the center.
Other Information on Gallium
1. How Gallium Is Produced
Gallium is produced only as a byproduct during the processing of ores of other metals, and its main raw material is bauxite, the main ore of aluminum, but it can also be extracted from zinc sulfide ore. In the Beyer method, Gallium accumulates in a sodium hydroxide solution during the processing of bauxite to alumina, so that Gallium metal can be obtained by electrolysis after the use of an ion exchange resin. For semiconductor applications, it is further purified by the zone melt process or single crystal extraction from melt, and very high purities such as 99.9999% are routinely achieved and commercially available.
2. Handling and Storage Precautions
Handling and storage precautions are as follows:
- Seal the container tightly and store in a dry, cool, and dark place.
- Use only outdoors or in well-ventilated areas.
- Avoid mixing with acids, alkalis, oxidizers, and halogens.
- Do not use on parts that may come in contact with metals, especially aluminum, as it will corrode them.
- Wear protective gloves and glasses when using.
- Wash hands thoroughly after handling.
- In case of skin contact, flush immediately with water.
- In case of eye contact, rinse cautiously with water for several minutes.