Structure refinements of superconducting Tl2Ba2CaCu2O8 and Tl2Ba2Cu3O10 from neutron diffraction data.

TL;DR: In this paper, the structure of the Tl-O planes of a single-crystal x-ray-diffraction (x-ray) X-ray diffraction (XRDF) was refined from neutron-powder diffraction data at both 150 and 13 K.

Abstract: The structures of ${\mathrm{Tl}}_{2}$${\mathrm{Ba}}_{2}$Ca${\mathrm{Cu}}_{2}$ ${\mathrm{O}}_{8}$ and ${\mathrm{Tl}}_{2}$${\mathrm{Ba}}_{2}$${\mathrm{Ca}}_{2}$ ${\mathrm{Cu}}_{3}$${\mathrm{O}}_{10}$ were refined from neutron-powder-diffraction data. The data for ${\mathrm{Tl}}_{2}$${\mathrm{Ba}}_{2}$Ca${\mathrm{Cu}}_{2}$ ${\mathrm{O}}_{8}$ were taken at 298 K, and the data for ${\mathrm{Tl}}_{2}$${\mathrm{Ba}}_{2}$${\mathrm{Ca}}_{2}$ ${\mathrm{Cu}}_{3}$${\mathrm{O}}_{10}$ were obtained at both 150 and 13 K. The results are essentially in agreement with the structural refinements based on single-crystal x-ray-diffraction data and confirm the positional disorder of the oxygen atoms in the Tl-O planes. The low-temperature refinements for ${\mathrm{Tl}}_{2}$${\mathrm{Ba}}_{2}$${\mathrm{Ca}}_{2}$ ${\mathrm{Cu}}_{3}$${\mathrm{O}}_{10}$ indicate that the symmetry remains tetragonal down to 13 K and that there is no significant structural change or discontinuity in the cell parameters through the superconducting critical temperature near 125 K.