Atomic-level structural changes in tin selenide revealed

Researchers from the FAMU-FSU College of Engineering and the National High Magnetic Field Laboratory have made an intriguing discovery regarding the compound tin selenide. They found that when tin selenide is heated, it undergoes atomic-level structural changes that enhance its electrical conductivity while reducing its thermal conductivity. This finding has significant implications for various applications such as refrigeration and waste heat recovery in areas like cars and nuclear power plants. The study, published in Nature Communications, sheds light on tin selenide’s unique thermoelectric properties, which could pave the way for sustainable power generation and other future uses.

Tin selenide has already garnered attention due to its exceptional thermoelectric coefficient at high temperatures, enabling it to generate a robust electric current from a temperature gradient. However, the reasons behind this phenomenon remained unclear. The researchers discovered that as the compound is heated, the bonds between tin and selenium remain largely unchanged, characterized by three short and several long bonds. However, the tin atoms within the compound begin to exhibit movement, transitioning from a fully ordered lattice structure to a partially disordered one.

The study revealed that this change represents an order-disorder phase transition, rather than a simple displacement of atoms. The mobility of the tin atoms allows tin selenide to scatter energy waves responsible for heat conduction. This dynamic partial disorder of tin atoms at elevated temperatures enables tin selenide to possess strong electrical conductivity while simultaneously reducing heat conductivity—a desirable combination for an efficient thermoelectric material.

The research involved collaboration between Theo Siegrist, a professor of chemical and biomedical engineering at the FAMU-FSU College of Engineering, scientists from Oak Ridge National Laboratory (ORNL), and the University of Tennessee, Knoxville. The team utilized ORNL’s spallation neutron source, a particle accelerator that generates bursts of neutrons by bombarding a target with protons. This neutron source facilitated the analysis of tin selenide’s crystal structure at the atomic level.

Studying the atomic-scale behavior of materials enables researchers to gain insights into the factors driving specific properties, which can be optimized for engineering purposes. Siegrist emphasized that this research is foundational, aiming to understand the mechanisms and influences at play in order to enhance the efficiency of energy conversion devices.

Source: Florida State University

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