Scientists unveil hidden secrets of gallium

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Nearly 150 years after its discovery, scientists at the University of Auckland have uncovered new and surprising properties of gallium, a metal known for its unique characteristics.

Gallium, first identified in 1875 by French chemist Paul-Émile Lecoq de Boisbaudran, is famous for its low melting point, which allows a gallium spoon to melt in a cup of tea.

It is also essential in making semiconductors.

Researchers have discovered unexpected behaviors of gallium at the atomic level.

Unlike most metals, gallium forms ‘dimers’—pairs of atoms—and is less dense as a solid than as a liquid, similar to how ice floats on water. Gallium’s atoms share electrons through ‘covalent bonds,’ which is unusual for metals.

A recent study found that these covalent bonds, which disappear when gallium melts, reappear at higher temperatures.

This discovery challenges long-held beliefs about gallium’s low melting point. The research, titled “Resolving Decades of Debate: The Surprising Role of High-Temperature Covalency in the Structure of Liquid Gallium,” was published in the journal Materials Horizons.

The researchers suggest that the key to gallium’s low melting point may be a large increase in entropy—a measure of disorder—when the bonds disappear, freeing up the atoms.

Professor Nicola Gaston from the University of Auckland and the MacDiarmid Institute for Advanced Materials and Nanotechnology stated that this finding overturns thirty years of assumptions about liquid gallium’s structure.

The study was led by Dr. Steph Lambie, now a postdoctoral researcher at the Max-Planck Institute for Solid State Research in Germany, along with Professor Gaston and Dr. Krista Steenbergen from Victoria University of Wellington and the MacDiarmid Institute.

Lambie, while a Ph.D. student, carefully reviewed decades of scientific literature and temperature data to piece together the complete picture of gallium’s behavior.

Understanding how gallium changes with temperature is crucial for advances in nanotechnology, where scientists manipulate materials on a tiny scale to create new substances.

Gallium is used to dissolve other metals, helping to create liquid metal catalysts and ‘self-assembling structures’ where disordered materials become organized.

In a previous project, researchers, including Gaston, Lambie, and Steenbergen, created zinc ‘snowflakes’ by crystallizing zinc in liquid gallium. This highlights gallium’s potential in creating innovative materials.

Gallium was predicted before its discovery. Russian chemist Dmitri Mendeleev, who created the first periodic table in 1871, left gaps for elements yet to be discovered, including gallium. Extracted from minerals like bauxite, gallium is not found in its pure form in nature.

It is used in semiconductors, telecommunications, LEDs, laser diodes, solar panels, high-performance computing, and even in the aerospace and defense industries. It also serves as a mercury alternative in thermometers.

Interestingly, scientists are exploring gallium’s potential to preserve traces of past life on Mars. Researchers at the University of Auckland’s School of Environment and the Te Ao Mārama—Center for Fundamental Inquiry are investigating this possibility.

Named after Gaul, the ancient name for France, gallium reflects the nationality of its discoverer. This new understanding of gallium’s properties opens up exciting possibilities for future technological advancements.