| dc.description |
EXAFS measurements on all the cations in (NCCO) and (NACCO), A=Sr, Ca or Ba, x = 0.06 or 0.18, have been made using synchrotron radiation. Bond lengths (R), coordination numbers (N) and Debye - Waller factors have been obtained from the EXAFS analysis. The curved wave theory in the single-scattering approximation and the small-atom multiple-scattering theory have been applied to experimental EXAFS data and it is found that the latter gives a better fit. The plane contains a strong multiple-scattering contribution. Further, all the dopants (Ce, Sr, Ca and Ba) occupy the Nd site without affecting the basic structure. Doping affects the local structure around the substituents as reflected by the changes in R and values. The observed layer distortion (or large Cu - O - Cu angle deviation from linearity, ) is found to have an adverse effect on as observed in Ca or Ba doped NACCO samples. Further, it is realized that critical levels of charge carriers, oxygen vacancies and planar effects have a strong influence on the SC behaviour of the electron doped cuprates. |
