Study on the site preference of Ca in superconducting oxides Bi2Sr2−xCaxCuO6+δ (0.1≤x≤1.0)

摘要: Abstract A series of compound with the nominal composition Bi2Sr2 − xCaxCuO6 + δ (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0) were synthesized by sol–gel method. Constituent phases and crystal structure samples analyzed X-ray diffraction. It can be found that Ca-doped Bi-2201 system was composed phase containing Ca a small quantity Bi16(Sr,Ca)14O38. For unit cell Ca, chemical component site preference atoms characterized systematically transmission electron microscopy. With introduction atoms, Sr-sites have been occupied partially Ca2 + in cell, which leads to decrease lattice parameters c b when Ca-content x is below 0.6. Two types new orthorhombic lattices are formed substitution. One space group Pma2 as two nearest neighbor same Sr–O layer Ca2 +. Its a = 5.402 A, b = 5.313 A c = 24.272 A, respectively. When Sr ions second neighboring layers replaced ions, Pmn21 formed. close previous. The modulation vector lying a*–c* plane (Pma2 Pmn21). Bi/Ca-2201 (with Ca) (without coexist grain, described an intergrowth structure.