Maier, Bernd J.; Welsch, A.-M.; Mihailova, B.; Angel, R. J.; Zhao, J.; Paulmann, C.; Engel, J. M.; Marshall, W.G.; Gospodinov, M.; Petrova, D.; Bismayer, U. (2011): Effect of la doping on the ferroic order in Pb-based perovskite-type relaxor ferroelectrics. In: Physical Review B - Condensed Matter and Materials Physics, Vol. 83, Nr. 13
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The structural alteration induced by the substitution of three-valent cations with an isotropic electronic outermost shell for Pb2+ in perovskite-type relaxors was investigated in the solid solutions Pb 1-xLaxSc(1+x)/2Ta(1-x)/2O 3, x =0.08 (PST-La) and Pb1-xLaxSc (1+x)/2Nb(1-x)/2O3, x =0.23 (PSN-La). In order to distinguish the \"charge\" effects from \"strain\" effects associated with the incorporation of La3+ in the structure, Sr-containing PbSc0.5Nb0.5O3 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 La3+ strongly affects the ferroic structural species due to strain effects through a disturbance of the system of lone-pair electrons associated with Pb2+ and a decrease in the tolerance factor. La doping suppresses the dynamical coupling between off-centered Pb and B-site cations and enhances antiphase BO6 octahedral tilting which, depending on the level of doping, may lead to long-range order of antiphase BO6 tilts at ambient conditions and frustrated antiferroelectric order of Pb ions at low temperatures.