Two new perovskites,(Bi_(0.5)A_(0.5))(Sc_(0.5)Nb_(0.5))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 describ...Two new perovskites,(Bi_(0.5)A_(0.5))(Sc_(0.5)Nb_(0.5))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 with combining macron]m space group,but shows local A-site displacements in the[100]direction.Both materials are highly disordered but illustrate the potential of(A)NbO_(3)-BiScO_(3)solid solutions as useful piezoelectrics or relaxors.展开更多
文摘Two new perovskites,(Bi_(0.5)A_(0.5))(Sc_(0.5)Nb_(0.5))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 with combining macron]m space group,but shows local A-site displacements in the[100]direction.Both materials are highly disordered but illustrate the potential of(A)NbO_(3)-BiScO_(3)solid solutions as useful piezoelectrics or relaxors.
