Superconducting current path and flux line shape in NbTiTa obtained by inter-diffusion process

Area of Science:

• Materials Science
• Condensed Matter Physics

Background:

• Superconducting wires are crucial for advanced technologies.
• Understanding the behavior of Niobium-Titanium-Tantalum (Nb-Ti-Ta) alloys is essential for optimizing superconducting properties.

Purpose of the Study:

• To comprehensively characterize the magnetic and transport properties of Nb-Ti-Ta superconducting wires.
• To investigate the relationship between microstructure and superconducting current flow.
• To determine the factors influencing critical current density and critical field.

Main Methods:

• Solid-state diffusion between Nb-12 at.%Ta alloy and pure Ti.
• Magnetic and transport measurements.
• Microstructural analysis to correlate with physical properties.

Main Results:

• Superconducting currents confirmed to flow within the diffusion layer with steep composition variation.
• Flux line core size is not constant, being smaller at the center of the layer than at the borders.
• Optimal critical current density achieved with a diffusion layer composition of approximately Nb-32%Ti-10%Ta, heat-treated at 700°C for 120 hours.
• The optimized wire exhibits a higher upper critical field.

Conclusions:

• The superconducting behavior of Nb-Ti-Ta wires is optimized by intrinsic properties of the ternary alloy.
• The findings support the proposition of superconducting current flow within the diffusion layer.
• A potential design for flux line core shape is proposed based on experimental observations.