Order-disorder nature of ferroelectric BaTi2O5 -: art. no. 112903

Ferroelectric single crystals of BaTi2O5 have been studied in detail by Raman and high-resolution micro-Brillouin scattering with a focus on the central component of the relaxation mode over a wide temperature range (20-600 degrees C). A relaxation mode has been clearly observed in these single crystals. The temperature dependences of the relaxation time and integrated intensity of the relaxation mode are well reproduced by the extended semiclassical tunneling model. The ferroelectric phase transition shows, at least near the vicinity of T-c, an order-disorder nature. Our results indicate that the spontaneous polarization mainly resulted from the dynamic disorder of the Ti ions in the octahedra along the polar b axis of BaTi2O5. (C) 2005 American Institute of Physics.