Structural study of Sr(sub 2)CuO(sub 3+delta) by neutron powder diffraction

摘要

Average crystal structures of superconducting Sr(sub 2)CuO(sub 3+(delta)) synthesized at ambient pressure from a hydroxometallate precursor were refined from neutron powder diffraction data. A simplified model was used to fit the modulated superstructures. Both compounds have an oxygen deficient La(sub 2)CuO(sub 4)-type tetragonal T structure with O vacancies located in the CuO(sub 2) planes, not in the Sr(sub 2)O(sub 2) layers. This raises important questions about the superconductivity in Sr(sub 2)CuO(sub 3+(delta)) reported to be a 70 K superconductor.