Published online by Cambridge University Press: 21 February 2011
The domain structure and the commensurate - incommensurate transition of some niobates, with general formula A2BNb5O15 where A = Ba, Sr or Pb and B = Na or K, are examined by using electron microscopy and electron diffraction methods. A model of the commensurate phase at room temperature is proposed and the natureof the incommensurate phase is discussed.