Journal
ACTA CRYSTALLOGRAPHICA A-FOUNDATION AND ADVANCES
Volume 68, Issue -, Pages 117-123Publisher
WILEY-BLACKWELL
DOI: 10.1107/S0108767311040281
Keywords
relaxors; diffuse scattering; X-ray scattering; relaxation times
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Funding
- RFBR [11-02-00687-a]
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The available body of experimental data in terms of the relaxor-specific component of diffuse scattering is critically analysed and a collection of related models is reviewed; the sources of experimental artefacts and consequent failures of modelling efforts are enumerated. Furthermore, it is shown that the widely used concept of polar nanoregions as individual static entities is incompatible with the experimental diffuse scattering results. Based on the synchrotron diffuse scattering three-dimensional data set taken for the prototypical ferroelectric relaxor lead magnesium niobatelead titanate (PMNPT), a new parameterization of diffuse scattering in relaxors is presented and a simple phenomenological picture is proposed to explain the unusual properties of the relaxor behaviour. The model assumes a specific slowly changing displacement pattern, which is indirectly controlled by the low-energy acoustic phonons of the system. The model provides a qualitative but rather detailed explanation of temperature, pressure and electric-field dependence of diffuse neutron and X-ray scattering, as well as of the existence of a hierarchy in the relaxation times of these materials.
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