Phase transition of layered compound Ba1-xBi2+xTixNb2-xO9

Structure phase transitions of Ba1-xBi2+xTixNb2-xO9 have been observed in t he Raman spectra. For the case with x = 0.0, the end member BaBi2Nb2O9 disp lays a clearly distinct Raman spectrum with respect to the cases with x not equal 0. Later they have similar Raman spectra as that of other layered fe rroelectrics. Therefore, it is proposed that a ferroelectric-nonferroelectr ic phase transition takes place for the case of BaBi2Nb2O9. A preliminary a ssignment of the vibration modes is given. (C) 1999 Published by Elsevier S cience Ltd. All rights reserved.