Structural disorder in BZN-based pyrochlores

Abstract

Careful structural investigations have been carried out on the Bi 1.5ZnNb1.5O7 based dielectric system (of A 2 B 2O7 pyrochlore structure type) in an attempt to understand the origin and tolerance of relaxor behavior in such materials. A highly structured, characteristic diffuse intensity distribution was observed in electron diffraction patterns, which arises from static disordering caused by local short range ordering of Bi and Zn ions on the pyrochlore A sites and associated structural relaxation of the O'A 2 sub-structure. This structural disordering is not affected by B site substitution of the Nb5+ ions by Sn4+ or Ti4+ ions. The result is of significance for optimizing the dielectric properties of bismuth-based advanced ceramics.