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Enhancement of Bc2 and Birr in bulk MgB2 superconductors with SnO2 Additions
Physica C: Superconductivity and its Applications ( IF 1.7 ) Pub Date : 2020-08-19 , DOI: 10.1016/j.physc.2020.1353749
Danlu Zhang 1 , Michael D Sumption 1 , Edward W Collings 1 , C J Thong 2 , Matt A Rindfleisch 2
Affiliation  

Three (MgB2)1-x(SnO2)x samples with x ranging from 0 to 5 wt% were prepared by the in situ route to study the effect of tin dioxide additions on the superconducting properties of MgB2 bulk materials. All of the reacted samples were slightly Mg deficient although the starting Mg:B precursor powder ratio was 1:2. A heat treatment (HT) temperature of 700 °C with a dwell time of 30 min was used. XRD results showed evidence of peak shifts for MgB2 phases with SnO2 addition. The magnitude of the a-axis lattice constant change (0.361 ± 0.075 %) calculated for the 3 wt% doped samples is comparable in magnitude to that seen previously for the C-doped MgB2 bulks which exhibited enhanced BC2. The upper critical fields (BC2) and the irreversibility fields (Birr) were measured resistively in fields up to 14 T at 5 K to Tc. The best BC2 value at 20 K (15.2 T based on extrapolation) was seen for sample IS3 (x =3 wt%), and was comparable to the best BC2 values (≈ 15 T at 20 K) seen for C-doped MgB2 bulks. IS3 had a corresponding Birr = 10.8 T (20 K). The superconducting transition temperature (Tc) appeared to increase slightly with doping, although within the range of error bars (37.4 K to 37.6 K for 1.6 T BC2 increase at 20 K), in contrast to C doping which is accompanied by a significant decrease in Tc (39 K to 36 K for 3.8 % C doped MgB2 bulk). We attribute the observed increase in both BC2 and Birr for SnO2-additions to lattice strain caused by the introduction of precipitates within the grains.



中文翻译:

添加 SnO2 的块状 MgB2 超导体中 Bc2 和 Birr 的增强

通过原位途径制备了三个 (MgB 2 ) 1- x (SnO 2 ) x样品,其中x范围为 0 至 5 wt%,以研究二氧化锡添加对 MgB 2块状材料的超导性能的影响。尽管起始 Mg:B 前体粉末的比例为 1:2,但所有反应的样品都略微缺乏 Mg。使用 700 °C 的热处理 (HT) 温度和 30 分钟的停留时间。XRD 结果显示了添加SnO 2 的MgB 2相的峰位移的证据。的幅度为 3 wt% 掺杂的样品计算的 - 轴晶格常数变化 (0.361 ± 0.075 %) 在幅度上与先前对 C 掺杂的 MgB 2块体观察到的变化相当,后者表现出增强的B C2。上临界场 ( B C2 ) 和不可逆场 ( B irr ) 在 5 K 至T c 时高达 14 T 的场中进行电阻测量。样品 IS3 (x = 3 wt%) 在 20 K 下的最佳B C2值(基于外推法为 15.2 T )与 C 掺杂的最佳B C2值(≈ 15 T 在 20 K)相当MgB 2块状。IS3有一个对应的Birr  = 10.8 T (20 K)。超导转变温度 ( T c ) 似乎随着掺杂略有增加,尽管在误差条范围内(37.4 K 到 37.6 K,对于 1.6 T B C2在 20 K 增加),与 C 掺杂相反,掺杂伴随着显着的T c降低(对于 3.8% C 掺杂的 MgB 2块体,从39 K 到 36 K)。我们将观察到的 SnO 2添加的B C2B irr 的增加归因于由晶粒内引入沉淀物引起的晶格应变。

更新日期:2020-08-19
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