喷雾热分解制备Bi-2212前驱粉末的相演变和超导性能

Phase Evolution and Superconductivity of Bi-2212 Precursor Powder Prepared by Spray Pyrolysis

采用喷雾热分解技术制备高温超导Bi_(2)Sr_(2)CaCu_(2)O_(x)(Bi-2212)前驱粉末,并研究了粉末热处理过程中的相演变过程及线材的超导性能。结果表明,喷雾热分解制备的粉末平均粒度为3.03μm,颗粒为球状并呈弥散分布。粉末在热处理过程中的相演变包含4个过程:粉末在527℃下主要进行硝酸盐的分解和组元之间的初步反应;由于喷雾粉末具有很高的活性,在588℃时生成Bi_(2)Sr_(2)CuO_(x)(Bi-2201)相;喷雾粉末在780℃发生Bi-2212相的成相反应;在834℃时粉末完全融化。Bi-2212/Ag超导线材的热处理温度窗口很窄,最高热处理温度T_(max)变化±2℃时,临界电流Ic的降幅达到了31 A。Bi-2212/Ag超导线材的最佳T_(max)为885℃,在该温度条件下制得的线材临界电流Ic(4.2 K,0 T)达到最高值,约为486 A。前驱粉末的热处理气氛为氧气时,线材的临界电流可以进一步提高到712 A。

The Bi_(2)Sr_(2)CaCu_(2)O_(x)(Bi-2212)precursor powder was prepared by spray pyrolysis.The phase evolution during the heat treatment process and the superconductivity of wires were analyzed.Results show that the powder prepared by spray pyrolysis is spherical with the average particle size of 3.03μm and the dispersion distribution.The phase evolution during the heat treatment process of powder includes four main reaction processes.The decomposition of nitrate and the pre-reaction process between components occur firstly at 527°C.Then the Bi_(2)Sr_(2)CuO_(x)(Bi-2201)phase is formed at 588°C due to the high reactivity of spray powder.The Bi-2212 phase is generated at 780°C,and the powder is completely melted at 834.2°C.The heat treatment temperature window of the Bi-2212/Ag wire is very narrow.The critical current(Ic)is reduced by 31 A when the maximum heat treatment temperature(T_(max))is changed by±2°C.When the optimal T_(max)of Bi-2212/Ag wire is 885°C,the maximum Ic(4.2 K,0 T)is 486 A.The critical current is increased to 712 A in the oxygen atmosphere during heat treatment.