Structured Diffuse Scattering as an Indicator of Inherent Cristobalite-like Displacive Flexibility in the Rare Earth Zirconate Pyrochlore LaδZr1−δO2−δ/2, 0.49

Abstract

A detailed electron and X-ray powder diffraction study has been made of the compositional and displacive flexibility of the rare earth zirconate pyrochlore (1−δ)ZrO2·δLaO1.5=(La3+)δ(Zr4+)1−δO2−δ/2,δ∼0.5. The extent of the pyrochlore “solid solution” in specimens rapidly quenched from 1500°C is shown to be considerably narrower than previously reported and certainly less than 2 mol.% in width. A weak but highly structured and quite reproducible diffuse intensity distribution in the form of {110}*polarized sheets of diffuse intensity perpendicular to each of the six 〈110〉 real space directions is observed in electron diffraction patterns and interpreted in terms ofβ-cristobalite-like 〈110〉 tetrahedral edge rotation of essentially rigid O(2)(La)4tetrahedra.