为了提高Bi-2212/Ag带的性能(主要指临界电流密度Jc),进行了部分熔化热处理工艺对带材Jc的实验.采用标准的4点法测量Jc,使用PW1700 XRD、SL20 SEM和EDX检验和研究带材的相组成和微观组织.实验表明:在流氧气氛下,烧结温度为860℃～880℃时,前驱粉末以Bi-2212为主相,同时含有少量的Bi-2201相、(Sr,Ca)Cu2O3相和富(Bi,Sr)相.在流氧气氛下,带材Jc性能对热处理工艺参数非常敏感.在实验条件范围内,优化后的热处理工艺参数为:熔化温度Tmax=890℃,熔化时间tmax＝10 min,冷却速率Rc＝2℃h-1;在保温温度为835℃时,保温时间ta=20 h,通过优化的部分熔化热处理工艺,在77 K、0 T下最后所制得带材的最大Ic=6 A,Jc=890 Acm-2.
In order to improve the performances of Bi-2212/Ag tapes (mainly refer to crital current density Jc), the experiment for effects of partial melting process on Jc of the tapes was conducted. Standard 4-point method was used to measure Jc. PW1700 XRD, XL20 SEM and EDX were used to exam and study phase constitution and microstructure of the tapes. The results indicate that sintered at 860℃~880℃ in flowing oxygen atmosphere, Bi-2212 precursors have primary phase of Bi-2212 and a slight amount of Bi-2201 phase, (Sr, Ca) Cu2O3 phase and rich (Bi,Sr) phase. In flowing oxygen atmosphere, processing parameters have critical effects on Jc of the Bi-2212/Ag tape. The optimized processing parameters are that melting temperature Tmax is 890℃, melting time tmax is 10 min and cooling rate Rc is 2℃/h. At 835℃, the optimized holding time ta is 20 h. By optimizing partial melting process, the maximum Ic of the final tapes is 6 A and Jc is 890 A/cm2 at 77 K,0 T.
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