An analysis was performed on bismuth strontium calcium copper oxide (Bi2Sr2CaCu2Ox, Bi2212). Researchers have discovered that the capabilities of this superconducting material are restricted by bubble formation during the development process.
The Bi2212 is a high temperature superconductor material that can be shaped into round wire and offers the desired versatility for constructing magnets. It has potential applications in particle accelerators and medical imaging.
The superconducting wires must have the capacity to produce a high current density and should control it in high magnetic fields to make it suitable for use in magnets. However, the Bi2212 material lacks this capability and this limits the application in the magnet technology.
The fabrication of the superconducting wires is carried out using the powder-in-tube process. Here, the Bi2212 powder is filled within silver tubes and molded to the required dimension. The multiple filaments present inside the Bi2212 powder are melted and then cooled slowly. This enables the reformation of the Bi2212 and significantly increases the current density.
Researchers then cooled the samples at various stages of the melting phase and used a synchrotron X-ray microtomography and scanning electron microscope to view the internal structure of the wires. It was found that minute powder pores join to form large bubbles during the melting phase.
These findings recommend that in order to enhance the Bi2212’s critical current density, the material can be made denser before melting.
A better approach to decrease or remove the formation of bubbles is to apply the densification process to the filaments at the final stage, thereby enhancing the powder-packing density from 60% to over 90%.
The study has been published in IOP’s journal Superconductor Science and Technology.