Raman spectra of the solid-solution between Rb2La2Ti3O10 and RbCa2Nb3O10

A site preference of niobium atom in Rb(2-x)La(2)Ti(3-x)Nh(x)O(10) (0.0 les s than or equal to x less than or equal to 1.0) and RbLa2-xCaxTi2-xNb1+xO10 (0.0 less than or equal to x less than or equal to 2.0), which are the sol id-solutions between Rb2La2Ti3O10 and RbCa2Nb3O10, has been investigated by Raman spectroscopy. The Raman spectra of Rb2-xLa2Ti3-xNbxO10 (0.0 less tha n or equal to x less than or equal to 1.0) gave an evidence that niobium at oms substituted for titanium atoms preferably occupy the highly distorted o uter octahedral sites rather than the central ones in triple-octahedral per ovskite layers. In contrast, the Raman spectra of RbLa2-xCaxTi2-xNb1+xO10 ( 0.0 less than or equal to x less than or equal to 2.0) showed no clear info rmation for the cationic arrangement in perovskite slabs. This difference i ndicated that a site preference of niobium atoms is observed only when the linear Rb-O-Ti linkage can be replaced by much stronger terminal Nb-O bond with double bond character. From comparison with the Raman spectroscopic be havior of CsLa(2-x)A'xTi2-xNb1+xO10 (A' = Ca and Ba; 0.0 less than or equal to x less than or equal to 2.0), it is also proposed that a local differen ce in arrangement of interlayer atoms causes a significantly different soli d acidity and photocatalytic activity of the layered perovskite oxides, des pite their crystallographically similar structures.