Stoichiometry and doping mechanism of the cubic pyrochlore phase in the system Bi2O3–ZnO–Nb2O5

Abstract

The subsolidus phase diagram of the system Bi₂O₃–ZnO–Nb₂O₅ in the region of the cubic pyrochlore phase has been determined at 950 °C. This phase forms a solid solution area that does not include the so-called ideal composition P, Bi₃Zn₂Nb₃O₁₄. It may be described in terms of two compositional variables: ZnO deficiency compared to P together with variable Bi : Nb ratio. Density measurements, preliminary crystallographic studies and the phase diagram indicate the solid solutions to have general formula, Bi_3+yZn_2−xNb_3−yO_14−x−y: −0.11(1) ≤ y ≤ 0.14(1) and −0.03(1) ≤ x ≤ 0.31(1).