Systematics in Bi-2201, -2212 and -2223 superconductors studied by positron annihilation radiation measurements

Positron lifetimes in Bi2Sr2Ca(n−1)CunO(2n+4+δ) or Bi-22(n−1)n superconducting compounds for n=1, 2 and 3 have been determined from positron annihilation lifetime (PAL) spectroscopy of associated γ-radiations. Bulk lifetime is shown to increase systematically with increase of n, the number of CuO2-layers in the Bi-22(n−1)n compound. Positron annihilation probing of structural units of this perovskite-like crystal system has thus been demonstrated.