Horiuchi S, Hirasaka M, Tsutsumi M, Kosuda K, Szerer M Y, Ben-Dor L
National Institute for Research in Inorganic Materials, Ibaraki, Japan.
Microsc Res Tech. 1995 Feb 15;30(3):258-64. doi: 10.1002/jemt.1070300307.
Microstructures of Bi(Pb)-family 2212 superconductors, which were prepared by a sol-gel method with three different compositions, were examined mainly by scanning and transmission electron microscopy. The magnetization of the specimens strongly depends on the ratio between Bi and Pb content, while Tc is almost constant. In specimen 1, prepared with the nominal composition of Bi/Pb = 9/1, small grains of 2212 phase are formed with a minor fraction of some impurity phases. In specimen 2, with Bi/Pb = 17/3, which is optimum from the viewpoint of magnetization, large grains of the 2212 phase are formed during heating at 800 degrees C, also with the impurity phases. In specimen 3, with Bi/Pb = 8/2, the 2212 grains are divided by layers of (Bi0.86, Pb0.14) (Ca0.7, Sr0.3)Ox. Moreover, plate-like 2212 crystals are severely bent so that small cracks appear often with an inclusion of amorphous substance being rich in Ca and Pb. These layers and cracks must degrade the magnetization. A modulated structure of Bi-type is formed in the 2212 grains of specimens 1 and 2, while not only Bi-type but also Pb-type are formed in specimen 3. The wavelength of Bi-type is different for each specimen.
采用溶胶 - 凝胶法制备的三种不同成分的铋（铅）系2212超导体的微观结构，主要通过扫描电子显微镜和透射电子显微镜进行了研究。样品的磁化强度强烈依赖于铋和铅含量的比例，而临界温度几乎保持恒定。在标称组成为铋/铅 = 9/1的样品1中，形成了2212相的小晶粒，同时还有少量的杂质相。在铋/铅 = 17/3的样品2中，从磁化角度来看这是最佳比例，在800摄氏度加热过程中形成了2212相的大晶粒，同样伴有杂质相。在铋/铅 = 8/2的样品3中，2212晶粒被（Bi0.86，Pb0.14）（Ca0.7，Sr0.3）Ox层分隔。此外，板状的2212晶体严重弯曲，因此经常出现小裂纹，并且包含富含钙和铅的非晶质物质。这些层和裂纹必定会降低磁化强度。在样品1和样品2的2212晶粒中形成了铋型调制结构，而在样品3中不仅形成了铋型，还形成了铅型。每个样品中铋型的波长都不同。
