Structural aspects of pyrochlores stability: influence of the cations in [8]A, [6]B positions and lattice parameters.

The influence of mole fraction and nature of the cations in positions ^[8]A and ^[6]B of the pyrochlores containing Na⁺, Ca²⁺, Cd²⁺, U⁴⁺, Nb⁵⁺, Ta⁵⁺, Ti⁴⁺, Sb⁵⁺, Zr⁴⁺, V³⁺, V⁴⁺, W⁵⁺, W⁶⁺ synthesized under hydrothermal conditions at 800 °C, 200 MPa and controlled oxygen fugacity in NaF solution of 1.0 mol·kg⁻¹ H₂O on lattice parameters has been considered. The unit cell parameters of the fluorpyrochlores where for Nb⁵⁺ or Ta⁵⁺ were substituted by other cations showing distinct linear variations from the effective cations radii in positions ^[8]A and ^[6]B. Based on the literary data analysis, the two-parameter nonlinear equation describing dependence of pyrochlore lattice parameters on the cation radii for the oxide-pyrochlores has been proposed. [ABSTRACT FROM AUTHOR]