Nanoparticles enhance properties of Bi-2223 superconductors

Superconductors are materials that reportedly do not offer electrical resistance to the flow of current upon being cooled down below a certain critical temperature. Typically, superconductors have a low critical temperature, close to absolute zero. However, a class of superconductors, known as high-temperature superconductors (HTS), have a critical temperature above 77 Kelvin, and have been used previously for the development of superconducting devices.

Bismuth strontium calcium copper oxide, known as BSCCO, is a class of HTS that has been studied and used in engineering, medical equipment, mining and transport systems. One of its members, (Bi_1.6Pb_0.4)Sr₂Ca₂Cu₃O₁₀ or Bi-2223, possesses a high superconducting critical temperature and could be suitable for potential applications. However, limitations such as a weak critical current density have hindered the development of Bi-2223 superconductors.

To address these shortcomings, researchers led by Professor Muralidhar Miryala from the Shibaura Institute of Technology and Professor Awang Kechik Mohd Mustafa from Universiti Putra Malaysia have investigated the effects of graphene nanoparticles addition on the phase formation and superconducting properties of Bi-2223.

“In this study, we report the effects on the critical temperature, critical current density, and structural and morphological properties of Bi-2223, when graphene nanoparticles are integrated into them using a novel co-precipitation method,” Miryala said.

Since graphene possesses excellent electrical, mechanical and chemical properties, and both graphene and Bi-2223 are grown as sheet-like microstructures, graphene nanoparticles are appealing as additives. The researchers studied the phase formation and crystal structures of different Bi-2223 examples with 0.3, 0.5 and 1.0 weight per cent graphene nanoparticles, using X-ray diffraction (XRD), and compared them to those of a pure sample. They also explored the critical temperature of the samples using alternate current susceptometry (ACS).

The XRD results revealed that a primary Bi-2223 phase and a secondary Bi-2212 phase, another BSCCO, dominated the samples. The volume fraction constituted by the Bi-2223 phase was higher for samples with 0.3 and 0.5 weight per cent graphene and slightly lower for the sample containing 1.0 weight per cent graphene. ACS analysis found that the onset critical temperature, phase lock-in temperature and coupling peak temperature decreased with an increase in graphene addition.

“These results suggest that the addition of graphene nanoparticles, acting as impurities, have the potential to enhance the current density of Bi-2223 superconductors,” Miryala said.

Explaining the potential future applications of Bi-2223 superconductors with enhanced current density, Miryala said they could facilitate diverse fields, like MRI imaging, power generation and distribution, renewable energy integration, particle accelerators, electronics and quantum computing. The research findings were published in the journal Nanomaterials.

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