Direct experimental evidence for the local oxygen non-stoichiometry in electron-doped Nd2-xCexCuO4-δ

Abstract A direct evidence is obtained for the local oxygen non-stoichiometry in T ′-type Nd 2− x Ce x CuO 4−δ using a high resolution analytical SEM technique. A correlation between the oxygen non-stoichiometry and superconductivity is established. It is found that the oxygen content increases from the grain boundary towards the interior of a superconducting grain, suggesting a gradual fall in T c towards the core. Our results reveal that critical levels of carriers and oxygen vacancies are essential for the T ′-type cuprates to exhibit superconductivity.