Abstract
The structural alteration induced by the substitution of three-valent cations with an isotropic electronic outermost shell for Pb in perovskite-type relaxors was investigated in the solid solutions PbLaScTaO, 0.08 (PST-La) and PbLaScNbO, 0.23 (PSN-La). In order to distinguish the “charge” effects from “strain” effects associated with the incorporation of La in the structure, Sr-containing PbScNbO was characterized as well. The structure of the compounds was analyzed by in situ Raman spectroscopy, single-crystal x-ray diffraction, and powder neutron diffraction at different temperatures or pressures. It is shown that the embedding of La strongly affects the ferroic structural species due to strain effects through a disturbance of the system of lone-pair electrons associated with Pb and a decrease in the tolerance factor. La doping suppresses the dynamical coupling between off-centered Pb and -site cations and enhances antiphase O octahedral tilting which, depending on the level of doping, may lead to long-range order of antiphase O tilts at ambient conditions and frustrated antiferroelectric order of Pb ions at low temperatures.
5 More- Received 16 January 2011
DOI:https://doi.org/10.1103/PhysRevB.83.134106
©2011 American Physical Society