Scientists design new copper-free high-temperature superconductors

Superconductivity is a central phenomenon for several existing and future technologies. This is the ability of certain materials to conduct electrical current with no resistance. 

Although superconductivity is in high demand, its practicality is hindered by the need for temperatures nearing absolute zero (-273 degrees Celsius or -460 degrees Fahrenheit).

However, since 1987, high-temperature superconductivity has emerged as a solution offering materials (predominantly copper oxide or cuprates) that exhibit superconductivity at 30 Kelvin (-243 degrees Celsius or -406 degrees Fahrenheit).

Scientists have recently found a new group of materials that show high-temperature superconductivity. The study, led by researchers at the National University of Singapore (NUS), details the design and synthesis of an oxide compound that does not contain copper at all.

The nickel-oxide compound “(Sm-Eu-Ca)NiO₂” is the first copper-free high-temperature superconducting oxide that works without requiring special pressure conditions since the discovery of cuprates in 1987.

Making predictions

Most high-temperature superconducting materials require extremely high pressures to exhibit superconductivity. Maintaining such high pressures requires expensive equipment, which makes integrating them into practical devices challenging.

Driven by this challenge, the researchers studied the inner structures of superconducting materials, which often contain multiple layers. They identified a direct correlation between superconducting temperatures and interlayer interactions.

This is to say that modifying the interlayer reactions could affect the temperature at which these materials show superconducting properties.

Based on this, the researchers developed a phenomenological model that could predict several copper-free compounds capable of exhibiting high-temperature superconductivity.

Phenomenological models are used in scientific research when focusing on the observable measurements between variables instead of the underlying mechanisms.

Their model predicted the nickel oxide compound (Sm-Eu-Ca)NiO₂ as being able to exhibit high-temperature superconductivity.

Confirming high-temperature superconductivity

Once the model predicted the compound, the researchers synthesized a highly crystalline, pure-phase material.

In other words, the synthesized material had a highly ordered structure of the constituent atoms and contained minimal structural defects and impurities. This is essential to verify because impurities and structural defects in a material can affect its superconducting properties.

Therefore, the structural perfection and purity of the material ensure that the superconductivity observed is an intrinsic property of the material and not a result of imperfections or defects.

Researchers confirmed that the nickel oxide material showed zero electrical resistance at temperatures nearing 40 Kelvin (-233 degrees Celsius or -388 degrees Fahrenheit). This was observed under ambient pressure at sea level, meaning no special pressure conditions were required.

The material was shown to be highly stable under ambient conditions, making it highly accessible for use in practical devices.

In a press release, co-author Dr. Chow stated, “This finding suggests that unconventional high-temperature superconductivity is not exclusive to copper but could be a more widespread property among elements in the periodic table.”

“This observation has profound implications for both theoretical understanding and experimental realization of a broader scope of superconducting materials with practical applications in modern electronics,” added Prof. Ariando.

The researchers plan to conduct further experiments by doping or adding impurities to the material, which change its electronic properties. They also plan to study changes in superconducting properties upon application of uniform pressure to the material.

The findings of the study are published in Nature. 

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