Short and intermediate range structural and chemical order in the relaxor ferroelectric lead magnesium niobate

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Abstract
We have obtained a model of short and intermediate range atomic structure in the relaxor ferroelectric Pb(Mg1/3,Nb2/3)O3 (PMN) by pair-density function (PDF) analysis of pulsed neutron and synchrotron x-ray powder diffraction data. All atomic species are found to be displaced from their ideal cubic perovskite lattice sites in a manner consistent with an eight site crystallographic disorder model. Use of the pair-density function in analyzing the structure of PMN has allowed short and intermediate range displacement correlations to be explored. Our structural model shows strong local displacement correlations resulting in two structurally distinct regions. Here we show that this model is in agreement with observed electron diffraction patterns and high resolution transmission electron microscopy images, and examine how it may be used in interpreting them. Differences in the local structure of the two regions may be important in explaining the relaxor behavior.