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 Sr0,61Ba0,39Nb2O6 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 Sr0,61Ba0,39Nb2O6 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.