New substitutions and novel derivatives of the aurivillius phases, Bi<SUB>5</SUB>TiNbWO<SUB>15</SUB> and Bi<SUB>4</SUB>Ti<SUB>3</SUB>O<SUB>12</SUB>

We investigated isomorphous substitution of several metal atoms in the aurivillius structures, Bi5TiNbWO15 and Bi4Ti3O12, in an effort to understand structure-property correlations. Our investigations have led to the synthesis of new derivatives, Bi4LnTiMWO15 (Ln = La, Pr; M = Nb, Ta), as well as Bi4PbNb2WO15 and Bi3LaPbNb2WO15, that largely retain the aurivillius (n = 1) + (n = 2) intergrowth structure of the parent oxide Bi5TiNbWO15, but characteristically tend toward a centrosymmetric/tetragonal structure for the Ln-substituted derivatives. On the other hand, coupled substitution, 2TiIV &#8594; MV + FeIII in Bi4Ti3O12, yields new Aurivillius phases, Bi4Ti3-2xNbxFexO12 (x = 0.25, 0.50) and Bi4Ti3-2xTaxFexO12 (x = 0.25) that retain the orthorhombic noncentrosymmetric structure of the parent Bi4Ti3O12. Two new members of this family, Bi2Sr2Nb2RuO12 and Bi2SrNaNb2RuO12 that are analogous to Bi2Sr2Nb2TiO12, possessing tetragonal (I4/mmm) Aurivillius structure have also been synthesized