Properties and structures of R/sub 2-chi/A/sub chi/CuO/sub 4/ phases; R = La, Pr and Nd; A = Sr, Pb and Cd

Journal Article · Tue Feb 28 23:00:00 EST 1989 · Materials Research Bulletin; (USA)

DOI:https://doi.org/10.1016/0025-5408(89)90218-3· OSTI ID:5370676

Gopalakrishnan, J; Subramanian, M A; Torardi, C C; Attfield, J P; Sleight, A W ^[1]

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1. Du Pont de Nemours (E.I.) and Co., Wilmington, DE (USA). Central Research and Development Dept.

The R/sub 2/CuO/sub 4/ phases for R = Pr and Nd were prepared and found to be semiconducting as previously reported. Crystal structures of both compounds were examined by a profile refinements of neutron powder diffraction data. A series of phases of the type R/sub 2-chi/Sr/sub chi/CuO/sub 4/ which are isostructural with R/sub 2/CuO/sub 4/ for chi up to 0.1 were prepared and found to remain semiconducting. Chemical analysis indicates the presence of Cu/sup III/, yet these materials are not superconducting. This supports the view that R/sub 2/CuO/sub 4/ phases should be regarded as Mott insulators. A new series of phases possessing the tetragonal K/sub 2/NiF/sub 4/ structure appear in the Pr/sub 2-z/Sr/sub chi/CuO/sub 4/ system for 1.0{le} chi {le} 1.25. The new phases are semiconducting. The authors also find semiconductivity and not superconductivity for La/sub 2-chi/A/sub chi/CuO/sub 4/ where A is Pb or Cd. Reasons are discussed for why Ga, Sr, Ca and Na substitutions into La/sub 2/CuO/sub 4/ lead to superconductivity whereas the Pb and Cd substitutions do not.

• OSTI ID: 5370676
• Journal Information: Materials Research Bulletin; (USA), Journal Name: Materials Research Bulletin; (USA) Vol. 24:3; ISSN MRBUA; ISSN 0025-5408
• Country of Publication: United States
• Language: English

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