The effects of Mg doping on the microstructure and transport properties of internal tin-processed brass matrix Nb₃Sn superconductors

Abstract

The addition of Zn into Cu matrix has been proved to enhance the Sn activity and accelerate the formation of a Nb3Sn layer in internal tin-processed Nb3Sn wires. However, in our samples, Ti is doped in Sn cores, and during the reaction, Ti was observed to accumulate between the inner and outer sub-elements of the 1980-Nb-core multi-filamentary brass matrix wires. With the addition of Mg into the brass matrix, Ti accumulation between the sub-elements was significantly suppressed, which promoted Ti incorporation into the Nb3Sn layers. Meanwhile, the formed Nb3Sn layers exhibited smaller grain sizes. Compared to the brass (Cu-12wt%Zn) matrix wires, an improvement of critical current density (Jc) was found in the Cu-12Zn-0.2Mg matrix wires due to the incorporation of Ti into the Nb3Sn layer and the refinement of the Nb3Sn grain size. The irreversibility field (Birr) and maximum bulk pinning forces (Fp,max) were calculated from the Kramer plot by analyzing the Jc(B) curves. A small amount of Mg (0.2 wt%) doping into the Cu-12Zn matrix wires can increase the Birr value by about 0.5 T and the Fp,max value by about 3 ∼ 4 GN m−3 after the wires were heat treated between 670 °C and 730 °C. The non-Cu Jc of the Cu-12Zn-0.2Mg matrix wires reaches the maximum value of 1533 A mm−2 @12 T after heat treatment at 685 °C and decreases at higher temperatures.

Effect of carbon doping on magnetic flux pinning and superconducting performance in FeSe0.5Te0.5 single crystals

“…For either low T c or high T c a number of works have attempted to discover the origin of the peak effect in the magnetization. Depending on the particular system investigated, the origin has been found to have an association with different processes [25][26][27][28][29]. In order to shed light on the pinning mechanisms in the field region of the SMP in our samples, we studied the magnetic field dependence of the pinning force density F p .…”

New Microstructure Control for Internal Tin Processed Nb₃Sn Wires through Element Addition to Matrix

“…The data for 650 is the value just after the pre annealing. The holding time for the nal heat treatment is 100 h26 .…”

Effect of Zn addition and Ti doping position on the diffusion reaction of internal tin Nb3Sn conductors

“…Our laboratory samples had larger Nb barrier thicknesses compared with practical internal tin Nb 3 Sn strands. Therefore, when the non-Cu J c was calculated, we used an equivalent area fraction of the barrier in the non-Cu region, which was set as 10% with a slight overestimation, referring to that of typical practical internal tin Nb 3 Sn strands (6%-8%) [35,59].…”

“…Higher Sn activity should also promote nucleation of the Nb 3 Sn phase at the Nb/Nb 3 Sn interface. We have also recently demonstrated that co-doping of Zn and a small amount of Mg to the matrix leads to finer grain morphologies and better J c performances [35]. In early works, Mg was also reported as an effective additive to increase the layer growth rate [36], reduce the grain size [36,37], and improve the J c performance [36][37][38][39].…”