Direct observation of the formation of polar nanoregions in Pb(Mg$_{1/3}$Nb$_{2/3}$)O$_3$ using neutron pair distribution function analysis
ORAL
Abstract
Using neutron pair distribution function (PDF) analysis over the temperature range from 1000~K to 15~K, we demonstrate the existence of local polarization and the formation of medium-range, rhombohedrally ordered polar nanoregions (PNRs) in a prototypical relaxor ferroelectric Pb(Mg$_{1/3}$Nb$_{2/3}$)O$_3$. We estimate the volume fraction of the PNRs as a function of temperature and show that this fraction steadily increases from 0 \% to a maximum of $\sim$ 30\% as the temperature decreases from 650~K to 15~K. Below T$\sim$200~K the PNRs start to overlap as their volume fraction reaches the percolation threshold. We propose that percolating PNRs and their concomitant overlap play a significant role in the relaxor behavior of Pb(Mg$_{1/3}$Nb$_{2/3}$)O$_3$.
*Work at Los Alamos was carried out under the auspices of the US DOE/Office of Science. The data were collected at the NPDF beamline at LANSCE, Los Alamos which is supported by the U.S.Department of Energy.
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