| Abstract
| - Schematic drawing illustrating the local correlations among the directions of the A-site Bi/Zn displacements and the B-site Nb/Zn configurations in the A2B2O6O‘ = (Bi,Zn)2(Zn,Nb)2O7 pyrochlores. The correlations are determined by the bond valence requirements of the framework O atoms.
- Local cation environments in the pyrochlore dielectrics A2B2O6O‘ = (Bi,M)2(M,Nb)2O6O‘ (M = Zn,Fe) were determined from the extended X-ray absorption fine structure. The A cations and O‘ ions aredisplaced from their ideal positions, yielding the effective (4 + 2 + 2) coordination for the A cations.The A-cation displacements are directed toward a pair of the framework O atoms; the specific displacementdirections are determined by the nature of the A cations (i.e., Bi, Zn, Fe) and the local Nb/Zn (or Nb/Fe)B-site configurations. Local correlations among the atomic displacements and both [A4O‘] and [A2B2O]configurations provide near-ideal bond valence sums for all constituent species in these pyrochlorestructures.
|
