The inhibition of Nb₃Sn grain growth in the presence of ZrO₂ nanoparticles appears to be one of the most promising method for pushing the critical current densities of Nb₃Sn superconducting wires to levels that meet the requirements set for the Future Circular Collider. We have investigated the effect of ZrO₂ nanoparticles formed by the internal oxidation of Zr on the superconducting properties and microstructure of Nb₃Sn formed from Nb-1 wt%Zr, Nb-7.5 wt%Ta, Nb-7.5 wt%Ta-1 wt%Zr and Nb-7.5 wt%Ta-2 wt%Zr alloys. A monofilamentary wire configuration was used, with a 0.22 mm outer diameter Nb-alloy tube containing a core of powdered metal oxide (SnO₂, CuO or MoO₃) as oxygen source and successive deposits of Cu, Sn and Cu on the outer surface. As determined from inductive measurements, the layer critical current densities of the samples based on Nb alloys with internally oxidized Zr were superior to those based on Nb-7.5 wt%Ta. The samples based on Nb-7.5 wt%Ta-1 wt%Zr and Nb-7.5 wt%Ta-2 wt%Zr showed higher critical current densities at high magnetic fields (above 10–15 T), and upper critical fields exceeding 28.5 T at 4.2 K (99% normal state resistivity criterion). A record value of 29.2 T of the upper critical field at 4.2 K was obtained on samples based on Nb-7.5 wt%Ta-2 wt%Zr. Hypotheses are proposed and discussed for explaining this unexpected increase of the upper critical field, by considering the possible effects of non-oxidized Zr on the superconducting properties of Nb₃Sn and of the oxidized Zr on the formation and microchemistry of Nb₃Sn. Regardless of sample type the Nb₃Sn grains observed in our samples have an aspect ratio of 1.5–1.7. When compared in the short axis direction, the mean distance between grain boundary intercepts (lineal intercept method) is ∼40% smaller in the samples with internally oxidized Zr than in the reference samples based on Nb-7.5 wt%Ta. In the long axis direction the reduction is of 20%–30%.

在ZrO ₂纳米粒子的存在下抑制Nb ₃ Sn晶粒的生长似乎是将Nb ₃ Sn超导线材的临界电流密度提高到满足Future Circular Collider要求的水平的最有前途的方法之一。我们研究了Zr内部氧化形成的ZrO ₂纳米颗粒对Nb-1 wt％Zr，Nb-7.5 wt％Ta，Nb-7.5 wt％Ta-1形成的Nb ₃ Sn的超导性能和微观结构的影响。wt％Zr和Nb-7.5 wt％Ta-2 wt％Zr合金。使用单丝线结构，外径为0.22 mm的Nb合金管，其中包含粉末状金属氧化物（SnO ₂，CuO或MoO ₃）作为氧气源，并在其外表面连续沉积Cu，Sn和Cu。由电感测量确定，基于具有内部氧化Zr的Nb合金的样品的层临界电流密度优于基于Nb-7.5 wt％Ta的样品的层临界电流密度。基于Nb-7.5 wt％Ta-1 wt％Zr和Nb-7.5 wt％Ta-2 wt％Zr的样品在高磁场（10-15 T以上）下显示出更高的临界电流密度，并且上临界场超过28.5 T为4.2 K（99％正常态电阻率标准）。在基于Nb-7.5 wt％Ta-2 wt％Zr的样品上，在4.2 K时的上临界场的记录值为29.2T。通过考虑非氧化Zr对Nb ₃超导性能的可能影响，提出并讨论了假设，以解释上临界场的这种意外增加Sn和氧化Zr对Nb ₃ Sn的形成及微观化学的影响。无论样品类型如何，在我们的样品中观察到的Nb ₃ Sn晶粒的长径比均为1.5-1.7。当在短轴方向上进行比较时，内部氧化Zr的样品中晶界截距（线性截距法）的平均距离比基于Nb-7.5 wt％Ta的参考样品小40％。在长轴方向上减少了20％–30％。