Influence of Sr/Ca on the phase evolution mechanism,phase purity and critical current density of Bi-2212 wires  

作　　者：Zhenbao Li Guoqing Liu Gaofeng Jiao Xiaoyan Xu Qingbin Hao Kai Yao Jianfeng Li 

机构地区：[1]Superconducting Materials Research Center,Northwest Institute for Nonferrous Metal Research(NIN),Xi’an 710016,People's Republic of China

出　　处：《Superconductivity》2024年第4期98-108,共11页超导(英文)

基　　金：financially supported by the Key Research and Development Program of Shaanxi(Program No.2023‐YBGY‐428);the National natural Science foundation of China(No.52002333);the Science and Technology Planning Project in Weiyang District of Xi’an(No.202107);the National Key R&D Program of China(Grant No.2021YFB3800201);the National natural Science foundation of China(No.52277029).

摘　　要：Two batches of Bi‐2212 precursor powder with Sr/Ca=2.24,2.33 were prepared by the spray pyrolysis tech-nology.Then two Bi‐2212 superconducting wires marked as Line4 and Line8‐2 were prepared by the above powders.Line4 with Sr/Ca=2.24 showed much higher phase purity,higher texture and its critical current density(J_(c))was 1.5 times that of Line8‐2 with Sr/Ca=2.33.Their micro‐structure evolution was scrutinized by quenching each wire at 7 instantaneous moments during the partial melting process(PMP).Bi‐2212 was found to decompose into(Sr,Ca)_(14)Cu_(24)O_(x)(14:24AEC),Bi_(9)Sr_(11)Ca_(5)O_(x)(9:16CF),Bi‐rich liquid Bi‐2212 and Bi‐rich solid Bi‐2212 at the initial stage of PMP.When Bi‐2212 began to solidify,the above four phases reacted to generate Bi‐2212.By analyzing the particle size,the content and the composition variation for 14:24AEC,9:16CF as well as the composition variation for Bi‐2212 matrix in above 7 moments of PMP,the phase evolu-tion’s difference between two wires was finally confirmed.The formation energy of 14:24AEC was smaller compared with 9:16CF,while 9:16CF was faster on dynamics.14:24AEC determined the whole synthetic reac-tion’s rate of Bi‐2212,and Sr/Ca as well as its value fluctuation in Bi‐2212 precursor powder can decide both the timeline and the driving force of PMP.A larger Sr/Ca in Line8‐2 made it melt earlier compared with Line4,which led to its earlier timeline during the melting stage of PMP.While the more consistent phase evolution’s pace between 14:24AEC and 9:16CF in Line4 finally contributed a larger Sr/Ca after solidification.Both the larger Sr/Ca and its larger fluctuation in Line4 finally contributed to its faster phase evolution’s pace,higher phase purity,better texture and higher J_(c).The deep logic driving the phase evolution mechanism in Bi‐2212 wires was disclosed for the first time,which will be very helpful to the future improvement of J_(c)for Bi‐2212 wires.

关 键 词：The phase evolution mechanism in Bi-2212 WIRES Timeline in PMP The deep logic driving the phase evolution 14:24AEC Sr/Ca and its value fluctuation 

分 类 号：TG1[金属学及工艺—金属学]