Bi2Sr2CaCu2O8的晶体结构与超导性能

本文研究了Bi-Sr-Ca-Cu-O体系中理想成份为Bi₂Sr₂CaCu₂O₈化合物的超导性能和晶体结构。名义成份为BiSrCaCu₂O_5.5零电阻超导转变温度T_c(0)=81.5K。用X射线粉末衍射方法测定了Bi₂Sr₂CaCu₂O₈的晶体结构,其基本结构属体心四方晶系,空间群为D_4h¹⁷-l4/mmm,点阵常数a=3.825?,c=30.82?。每单胞化合式单位为2.2Ca占据2(a)等效点系,4Sr,4Bi和4Cu占据三组4(e)位置,其原子参数z分别为0.110,0.302和0.445,16O分别占据8(g),z=0.445和二组4(e),z=0.210和0.380。Bi₂Sr₂CaCu₂O₈晶体结构可认为是阳离子沿z轴的(00z)和((1/2)(1/2)z)交错排列,由Aurivillius相导生出来的。讨论了在Bi-Sr-Ca-Cu-O体系中可能存在的其它沿z轴不同堆垛层数的超导相。 关键词：

CRYSTAL STRUCTURE AND SUPERCONDUCTIVITY OF Bi2Sr2CaCu2O8 COMPOUND

The crystal structure of the ideal composition compound Bi₂Sr₂CaCu₂O₈ with zero resistance temperature T_c(0) = 81.4K had been determined by X-ray powder diffraction method. The basic structure of this compound exhibits tetragonal symmetry with lattice constants a = 3.825 ?, c = 30.82 ?. The most probable space group is D_4h¹⁷-14/mmm, Each unit cell contains two formula units. The arrangements of atoms in the unit cell are as follows:2Ca cations occupy 2(a) equivalent point position; 4Sr, 4Bi and 4Cu cations occupy the same equivalent point position 4(e) with respective parameters z= 0.110, 0.302, 0.445; 16O anions respectively occupy 8(g) (z = 0.445) and two 4(e) equivalent point positions (z= 0.210 and z = 0.380), The crystal structure of Bi₂Sr₂CaCu₂O₈ can be derived from Aurivillius type structure. The main feature of the structure is alternate arrangement of cations along (00z) and (1/2, 1/2, z) of tetragonal system. The other possible superconducting phases in the Bi-Sr-Ca-Cu-O system can be considered as the structure having different stacking layers along z axis.
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