Thermal strain-induced enhancement of electromagnetic properties in SiC-MgB2 composites

Abstract

Strain engineering has been used to modify materials properties in ferroelectric, superconducting, and ferromagnetic thin films. The advantage of strain engineering is that it can achieve unexpected enhancement in certain properties, such as an increase in ferroelectric critical temperature, Tc, by 300 to 500K, with a minimum detrimental effect on the intrinsic properties of the material. The strain engineering has been largely applied to the materials in thin film form, where the strain is generated as a result of lattice mismatch between the substrate and component film or between layers in multilayer structures. Here, we report the observation of residual thermal stress/strain in dense SiC-MgB2 superconductor composites prepared by a diffusion method. We demonstrate that the thermal strain caused by the different thermal expansion coefficients between the MgB2 and SiC phases is responsible for the significant improvement in the critical current density, Jc, the irreversibility field, Hirr, and the upper critical field, Hc2, in the SiC-MgB2 composite where the carbon substitution level is low. In contrast to the common practice of improving the Jc and Hc2 of MgB2 through chemical substitution, by taking advantage of residual thermal strains we are able to design a composite, which shows only a small drop in Tc and little increase in resistivity, but a significant improvement over the Jc and Hc2 of MgB2. The present findings open up a new direction for manipulation of materials properties through strain engineering for materials in various forms.

References in corpus (6)

• Giant anharmonicity and non-linear electron-phonon coupling in MgB${}_2$; A combined first-principles calculations and neutron scattering study
• Systematic effects of carbon doping on the superconducting properties of Mg(B${}_{1-x}$C${}_x$)${}_2$
• Carbon substitution in MgB2 single crystals: structural and superconducting properties
• Phonon Density-of-States in MgB2
• Large Upper Critical Field and Irreversibility Field in MgB2 wires with SiC additions
• Negative thermal expansion of MgB${}_2$ in the superconducting state and anomalous behavior of the bulk Grüneisen function