A study conducted by the Jawaharlal Nehru Centre for Advanced Scientific Research, Bengaluru, has unravelled the electronic mechanisms governing chemical bonding of a new class of materials called ‘incipient metals’, which can boost energy harvesting and power generation.

Sourcing new materials with unique properties can help in the advancement of current technology. Recently, scientists are turning to a class of compounds called group IV chalcogenides that have intriguing properties, making them suitable candidates for technological applications. These compounds contain an element from group VI of the periodic table combined with an element from group III–V of the periodic table, like PbTe, SnTe and GeTe, says a press release from the Department of Science and Technology, Government of India.

Chalcogenides can transition reversibly between amorphous and crystalline phases in response to changes in temperature, pressure, or electrical fields. This unique characteristic has practical applications in rewritable optical discs and electronic memory devices due to the contrasting optical responses of the two phases. Additionally, these chalcogenides are valuable in energy harvesting and power generation applications, thanks to their high electrical conductivity and effective conversion of thermal energy into electrical energy through the thermoelectric effect.

The study, by Professor Umesh Waghmare from the Theoretical Sciences Unit, explored the possibility of introducing the recently introduced metavalent bonding (MVB) within a single 2D layer of Group IV chalcogenides, investigating its mechanisms and the resulting consequences on material properties.

The theoretical work conducted by Prof Waghmare and his team has significant implications and promising applications across industries, the release says. The chalcogenides explored in this study are already employed in computer flash memories, utilising their ability to change optical properties during the transition from crystalline to amorphous states. Additionally, the potential use of these materials in energy storage, especially as phase change materials, opens avenues for more sustainable and efficient energy solutions.

Furthermore, the research connects with the emerging field of quantum materials, aligning with the goals of India’s national mission on quantum technology. These materials, with their distinct electronic structures and properties, offer a prototypical example of quantum topological materials, a critical component in advancing quantum technologies.

High entropy alloys

The reason stainless steel is useful is because the chromium in it forms an oxide layer that protects it from rusting. Today, scientists the world over are toying with multiple-metal alloys — more than five as opposed to two or three in conventional alloys — to make materials of desired properties. Under this ‘High Entropy Alloys’ are of interest because of their extreme sturdiness, which comes from the way the atoms are arranged in the alloys. One difficulty with developing HEAs is that you have to make them and test them.

Now a group of researchers at the Pacific Northwest National University has developed a tool to predict how HEAs will behave under high temperature oxidative environments. The tool helps investigate the arrangement of atoms within samples, using in situ atom probe tomography. This will fast-track development of complex alloys with exceptional high-temperature properties.

The group of researchers predominantly consists of people of Indian origin — Arun Devaraj, Bharat Gwalani, Anil Krishna Battu, Thevuthasan Suntharampillai and Aniruddha Malakar. “This work sheds light on the mechanisms of oxidation in complex alloys at the atomic scale,” says Bharat Gwalani, co-corresponding author of the study.

“Right now there are no universally applicable governing models to extrapolate how a given complex, multi-principal element alloy will oxidize and degrade over time in a high-temperature oxidation environment,” says Devaraj. The ultimate goal is to choose a combination of elements that favour the formation of an adherent oxide, he said. “You know oxide formation will happen, but you want to have a very stable oxide that will be protective, that would not change over time, and would withstand extreme heat inside a rocket engine or nuclear reactor.”