Ambient pressure synthesis and neutron structure analysis of YBa 2Cu 4O 8

Abstract

The high- T c superconductor YBa 2Cu 4O 8 has been synthesized by the solid state reaction of Y 2O 3 with a precursor matrix under ambient oxygen pressure. The final product is single phase 124 which shows zero resistance at 78.5 K ( ΔT c =2.0 K). DC magnetic susceptibility studies confirm the presence of a single bulk superconducting phase ( T c ≅82.5 K) and absence of 123 or 247 phases as impurities. Neutron profile refinement studies of the structure of the sample indicate vacancies at 9% of the linear chain oxygen sites, O(1); increased puckering of Cu(1)-0(1) layers, and a much reduced short-contact distance between neighbouring 0(1)-anions. Other notable features of the structure are vacancies (14%) at Ba-sites and unusually short bridging bond-length Cu(1)-0(4) and Cu(2)-0(4).