Structure of non-phase-separated La2CuO4.03 studied by single-crystal neutron diffraction

The structure of a La2CuO4+y single crystal with the excess oxygen content y = 0.03 has been studied by means of neutron diffraction at T = 13 K. Alth ough the extra oxygen content of y = 0.03 is inside the miscibility gap of La2CuO4+y (0.01 < y < 0.06), the crystal is not phase separated at low temp eratures. The sole phase constituting the sample has Cmca symmetry. It was confirmed that the extra oxygen, O4, is located close to the site (1/4, 1/4 , 1/4). The structural parameters for all atoms lay between those previousl y determined for the oxygen-poor and oxygen-rich phases representing the ed ges of the miscibility gap, y = 0.01 and 0.06, respectively. Our data allow us to conclude that (1) the phase-separated and non-phase-separated La2CuO 4+y compounds are structurally identical, and (2) the crystal structure of La2CuO4+y changes monotonically when the extra oxygen content changes from 0 to 0.05. (C) 1999 Elsevier Science B.V. All rights reserved.