Polar fluctuations of nanoscale size as a source of giant dielectric response of relaxor ferroelectrics

Characteristic frequencies of nanoscale polar fluctuations have been resolved by means of neutron diffuse scattering measurements on a Sr_0,61Ba_0,39Nb₂O₆ single crystal in the MHz-GHz frequency region. Comparison with dielectric measurements proved that these polar fluctuations are a source of giant dielectric response, whose temperature-frequency dependence is specific for a significant group of substances exhibiting a glass-type ferroelectric phase transition, so-called relaxor ferroelectrics.

(a) Typical domain structure of Sr_0,61Ba_0,39Nb₂O₆ with polar nanodomains and its characteristic disk-like diffuse scattering (b). Comparison of temperature dependence of diffuse scattering intensity obtained experimentally (c) on neutron spectrometers at Institut Laue-Langevin (Grenoble) and numerically (d) from a model based on dielectric data at various energy transfers.

¹Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 18221 Praha 8, Czech Republic
²Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France
³Institute of Materials Science, University of Silesia, Bankowa 12, PL-40-007 Katowice, Poland
⁴Institute of Electronic Materials Technology, 133 Wolczynska Street, 01-919 Warsaw, Poland