Studies of relaxor ferroelectrics with spontaneous polar nanoregions

0485831 - FZÚ 2018 CZ eng D - Thesis
Ondrejkovič, Petr
Studies of relaxor ferroelectrics with spontaneous polar nanoregions.
Univerzita Karlova, Matematicko-fyzikální fakulta. Defended: Praha. - Praha: Univerzita Karlova, 2017. 128 s.
R&D Projects: GA ČR GA16-09142S; GA ČR GA15-04121S
Institutional support: RVO:68378271
Keywords : relaxor ferroelectrics * strontium barium niobate * inelastic neutron scattering * phase-field simulations
OECD category: Condensed matter physics (including formerly solid state physics, supercond.)

The thesis is devoted to relaxor ferroelectrics with spontaneous polar nanoregions. We have investigated one of the canonical representatives, uniaxial strontium barium niobate, by means of neutron scattering, and also performed computer simulations with a model of a uniaxial ferroelectric with point defects. Neutron scattering studies of strontium barium niobate single crystals elucidate diffuse scattering which is associated mainly with the static ferroelectric nanodomain structure and dynamic order-parameter (polarization) fluctuations. Moreover, high-resolution neutron backscattering experiments allowed us to resolve characteristic frequencies of the order-parameter fluctuations and prove that this component is caused by the same polar fluctuations that are responsible for the Vogel-Fulcher dielectric relaxation. The model system with point defects exhibits relaxor-like physical properties which are associated with a distribution of crossover temperatures.

Permanent Link: http://hdl.handle.net/11104/0280771