Evidence of three types of short range ordered fluorite structure in the (1 − x) Y0.15Zr0.85O1.93 – x Y0.75Nb0.25O1.75 (0 ≤ x ≤ 1) system

Abstract

The microstructure of the high-temperature quenched oxides of the (1 − x) Y_0.15Zr_0.85O_1.93 – x Y_0.75Nb_0.25O_1.75 (0 ≤ x ≤ 1) system has been investigated by selected area electron diffraction and high resolution transmission electron microscopy. We have found three types of fluorite structure: the x = 0 end member of the solid solution (Y_0.15Zr_0.85O_1.93) shows evidence of tetragonal fluorite-type structure; we have also observed a modulated fluorite-type structure due to short-range ordering of the oxygen vacancies. The microdomain modulated structure gradually evolves from a distorted pyrochlore-type to a type intermediate between C-type and distorted pyrochlore as x decreases from 1 to 0.3.