DETERMINATION OF THE CRYSTAL STRUCTURE OF ERBIUM TITANATE, Er2Ti2O7, BY X-RAY AND NEUTRON DIFFRACTION

Abstract

The crystal structure of erbium titanate, Er2Ti2O7, has been shown by X-ray and neutron powder diffraction to be of the cubic pyrochlore type, with ao = 10.0762 ± 6 Å. Least-squares isotropic refinement based on resolved single reflections gave x(O2) = 0.4200 ± 10 and R = 2.25%. Ionic and neutral X-ray scattering factors gave practically identical results. The six equal Ti—O2 distances in the distorted coordination octahedron of the Ti atom are 1.955 ± 5 Å. The two short (apparent) Er—O distances are 2.1815 ± 5 Å (Er—O1) and 2.471 ± 8 Å (Er—O2). The infrared spectrum of the titanate in the region 1 600 to 250 cm−1 shows features similar to those encountered in the spectra of other simple oxygen compounds of titanium.