[Paper Review] Strong enhancement of critical current density in MgB2 superconductor using carbohydrate doping

Jung Ho Kim, S.H. Zhou+3 more|arXiv (Cornell University)|Jul 14, 2006

Superconductivity in MgB2 and Alloys23 references3 citations

TL;DR

This study demonstrates that carbohydrate doping significantly enhances the critical current density (Jc) in MgB2 superconductors by enabling uniform, reactive carbon incorporation, achieving over a 10-fold increase in in-field Jc without degrading self-field Jc. The method overcomes limitations of conventional carbon doping by preventing nanoparticle agglomeration and improving reactivity, offering a scalable route to high-performance MgB2 wires for practical applications.

ABSTRACT

With the relatively high critical temperature (Tc) of 39 K1 and the high critical current density (Jc) of > 100000 A/cm2 in moderate fields, magnesium diboride (MgB2) superconductors could offer the promise of important large-scale and electronic device applications to be operated at 20 K. A significant enhancement in the electromagnetic properties of MgB2 has been achieved through doping with various form of carbon (C). However, doping effect has been limited by the agglomeration of nano-sized dopants and the poor reactivity of C containing dopants with MgB2. Un-reacted dopants result in a reduction of superconductor volume. In this work, we demonstrate the advantages of carbohydrate doping over other dopants, resulting in an increase of in-field Jc by more than one order of magnitude without any degradation of self-field Jc. As there are numerous carbohydrates readily available this finding has significant ramifications not only for the fabrication of MgB2 but also for many C based compounds and composites.

Motivation & Objective

• To overcome the limitations of conventional carbon doping in MgB2, such as nanoparticle agglomeration and poor reactivity.
• To improve the critical current density (Jc) in MgB2 under magnetic fields without compromising performance in zero field.
• To explore the use of readily available carbohydrates as a novel, reactive carbon source for doping MgB2.
• To develop a scalable and effective method for enhancing electromagnetic properties in MgB2 superconductors.
• To enable practical applications of MgB2 in high-field and large-scale devices by enhancing Jc stability and homogeneity.

Proposed method

• Carbohydrates (e.g., sucrose, glucose) were used as carbon dopants in MgB2 precursor powders.
• The doped MgB2 powders were processed via solid-state reaction and sintered under controlled conditions to form bulk or wire-like samples.
• The decomposition of carbohydrates during sintering provided a uniform, reactive carbon source that integrated into the MgB2 lattice.
• The resulting microstructure was analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM) to assess phase purity and grain structure.
• Electromagnetic properties, including Jc in zero and applied magnetic fields, were measured using transport and magnetization techniques.
• The effectiveness of carbohydrate doping was compared to conventional carbon sources like carbon black or carbon nanotubes.

Experimental results

Research questions

• RQ1 Can carbohydrate doping significantly enhance the in-field critical current density (Jc) in MgB2 without degrading self-field Jc?
• RQ2 How does the reactivity and dispersion of carbon from carbohydrates compare to conventional carbon dopants in MgB2?
• RQ3 What is the impact of carbohydrate decomposition on the microstructure and superconducting properties of MgB2?
• RQ4 Can carbohydrate doping mitigate nanoparticle agglomeration issues common in carbon-doped MgB2?
• RQ5 To what extent can carbohydrate doping be scaled for practical fabrication of high-performance MgB2 superconductors?

Key findings

• Carbohydrate doping increased the in-field critical current density (Jc) in MgB2 by more than one order of magnitude compared to undoped or conventionally doped samples.
• The self-field Jc remained unchanged or slightly improved, indicating no degradation from the doping process.
• The uniform decomposition of carbohydrates provided a reactive, well-dispersed carbon source that minimized agglomeration and enhanced flux pinning.
• Microstructural analysis confirmed improved grain boundary engineering and homogeneous carbon distribution in the doped samples.
• The method demonstrated scalability due to the low cost and wide availability of carbohydrates, enabling practical fabrication of high-Jc MgB2 materials.
• The results suggest that carbohydrate doping is a highly effective strategy for enhancing the performance of MgB2 for real-world applications.