A new material was accidentally created on a space station

Aboard the China Space Station, a never-before-seen compound appeared.

An intermetallic compound (IMC) of copper and bismuth, Cu₂₀Bi₉, formed while scientists were studying the microgravity properties of a different alloy, Cu₇₅Sn₁₃Bi₁₂. Back on Earth, Qichao Zhong and Wenjun Xie identified this compound in both spaceflight and ground-parallel samples.

“The discovery of the Cu₂₀Bi₉ intermetallic compound came as a complete surprise to us,” Xie said. “Our original objective for the space solidification experiment on the Cu₇₅Sn₁₃Bi₁₂ alloy was to reveal the kinetics of the liquid phase separation and the evolution of the solidified microstructures under microgravity in space.”

IMCs have useful structural and mechanical characteristics, and the physical structures of bismuth-containing IMCs can be particularly unique and advantageous. However, they typically only form under extreme experimental conditions.

“It attracted our interest mainly because no intermetallic phases exist in the binary Cu-Bi alloy system under ambient pressure, and all previously reported Cu-Bi IMCs were synthesized under high-pressure conditions,” Xie said.

The researchers found the same type of Cu₂₀Bi₉ can be easily created on the ground as well as in space. A unit cell is comprised of 80 copper atoms and 36 bismuth atoms and “looks like a square candy box,” according to Xie. Using models, they showed the material has impressive stability, with individual atoms that only experience small displacements.

The group is working to better understand how Cu₂₀Bi₉ forms and why it seems to only form within the Cu₇₅Sn₁₃Bi₁₂ system. They are also further exploring the IMC’s chemical and physical properties for practical uses in both terrestrial and space environments.

Source: “A tetragonal Cu₂₀Bi₉ intermetallic compound phase discovered in Cu₇₅Sn₁₃Bi₁₂ alloy,” by Q. C. Zhong and W. J. Xie, Journal of Applied Physics (2026). The article can be accessed at https://doi.org/10.1063/5.0342394 .