Structural characteristics of pyrochlore formation

Abstract

By calculating the value of the unknown oxygen positional parameter x for a large number of A³⁺₂B⁴⁺₂O₇ pyrochlores, it was determined that increasing the radius of the A cation in a series of constant B increased the value of x, and that increasing the radius of the B cation in a series of constant A decreased the value of x. The region of pyrochlore formation has a range of x values from 0.404 to 0.432 and contains BO₆ polyhedra that closely approach O_h symmetry and AO₈ polyhedra that are highly deformed. It was shown that the characteristics of the BO₆ polyhedra were the most important in determining whether or not a pyrochlore would form.