Local structure of relaxor ferroelectric SrxBa1-xNb2O6 from a pair distribution function analysis
Date
2019
Authors
Pasciak, M.
Ondrejkovic, P
Kulda, J
Vanek, P
Drahokoupil, J
Steciuk, G
Palatinus, L
Welberry, Thomas Richard
Fischer, H E
Hlinka, J
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American Physical Society
Abstract
Pair distribution function analysis of neutron-scattering data and of ab initio molecular dynamics results have been employed to study short-range structural correlations and their temperature dependence in a heavily disordered dielectric material SrxBa1-xNb2O6 (x = 0.35, 0.5, and 0.61). Intrinsic disorder caused by a partial occupation of the cationic sites by differently sized Sr and Ba atoms and their vacancies introduces important local strains to the structure and directly influences the Nb-O-6 octahedra tilting. The resulting complex system of tilts is found to be both temperature and Sr-doping sensitive with the biggest tilt magnitudes reached at low temperatures and high strontium contents, where ferroelectric relaxor behavior appears. We find evidence for two Nb-O-6 subsystems with different variations of niobium-oxygen bond lengths, distinct dynamics, and disparate levels of deviation from macroscopic polarization direction. These findings establish a detailed picture of the local structure of SrxBa1-xNb2O6 and provide a deeper insight into the origins of the materials dielectric properties.
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Physical Review B
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Journal article
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