Crystal Structure of Tetragonal YBa₂Cu_3-δCo_δO_7-γ (δ=0, 0.3)

Abstract

Crystal structures of tetragonal YBa 2 Cu 2.7 Co 0.3 O 7-γ and tetragonal YBa 2 Cu 3 O 7-γ are determined by X-ray and TOF neutron powder diffractometries. Structural parameters are obtained by the Rietveld profile refinement method. In YBa 2 Cu 2.7 Co 0.3 O 7-γ' , cobalt atoms preferentially occupy one of the copper sites at 1a(0 0 0) rather than the 2g(0 0 z ) site with z ∼0.36. The lattice constants are a = 3.8644(2)Å and c = 11.7881(9)Å for the quenched YBa 2 Cu 3 O 6.15 and a = 3.8752(2)Å and c = 11.6851(9)Å for the furnace-cooled YBa 2 Cu 2.7 Co 0.3 O 6.81 .