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Welsch, A.-M.; Maier, Bernd J.; Engel, J. M.; Mihailova, B.; Angel, R. J.; Paulmann, C.; Gospodinov, M.; Friedrich, A.; Stosch, R.; Güttler, B.; Petrova, D.; Bismayer, U. (2009): Effect of Ba incorporation on pressure-induced structural changes in the relaxor ferroelectric PbSc0.5 Ta0.5 O3. In: Physical Review B - Condensed Matter and Materials Physics, Vol. 80, No. 10
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Pressure-induced structural changes in the canonical relaxor Pb0.78 Ba0.22 Sc0.5 Ta0.5 O3 were studied with both in-house and synchrotron single-crystal x-ray diffraction as well as Raman spectroscopy at pressures up to 9.8 GPa. The results reveal that the substitution of Ba for Pb in AB O3 perovskite-type structures, i.e., the substitution of a two-valent element with an isotropic electron shell for an isovalent element with a stereochemically active lone pair, leads to a \"diffuse pressure-induced phase transition,\" a structural transformation over a broad pressure range, without a well-defined critical pressure point. The smeared phase transition of the average structure results from the existence of local structural deformations in the vicinity of A-positioned Ba cations.