Low temperature synthesis route and structural characterization of (Bi(0.5)A(0.5))(Sc0.5Nb0.5)O-3 (A = K+ and Na+) perovskites

摘要

Two new perovskites, (Bi(0.5)A(0.5))(Sc0.5Nb0.5)O-3 where A = K+ and Na+, have been made phase pure for the first time. The synthesis procedure that prevented the formation of pyrochlore impurities is described. B- site ordering in A = K+ is successfully achieved by prolonged heating. Combined Rietveld refinement on synchrotron X- ray diffraction and neutron diffraction data is used to determine the complex average structure of these materials. A = Na+ crystallizes in the tetragonal P4/mbm space group and has disordered a(0)a(0)c(+) rotations of BO6 octahedra. A = K+ crystallizes in the cubic Pm (3) over barm space group, but shows local A- site displacements in the [100] direction. Both materials are highly disordered but illustrate the potential of (A) NbO3-BiScO3 solid solutions as useful piezoelectrics or relaxors.