A systematic study of the temperature dependence of the superlattice reflections has been carried out using anomalous x-ray scattering technique in a single crystal Pb(Mg 1/3 Nb 2/3 )O 3 (PMN). Two types of nanodomains were found to exist in PMN: a) chemically ordered nanodomains, and b) polar regions formed by short-range correlated ionic displacements. Each type of nanodomains gives rise to superlattice reflections at different locations in the reciprocal space. From the temperature dependence of the superlattice peaks, corresponding to polar nanodomains, we found a second order structural phase transition near T f =220 K. This transition corresponds to the freezing of correlated oxygen octahedra rotations with temperature-independent correlation radius of 40 Å below T f . Chemical nanodomains due to short-range order on the B sites were shown to exhibit isotropic shape and temperature independent size of 50 Å in 15-800 K interval. Anomalous diffraction near Pb L III absorption edge has shown that Pb displacements are not random at low temperatures, but correlated on the short-range scale.
|State||Published - 1 Jan 2001|
|Event||6th International Symposium on Ferroic Domains and Mesoscopic Structures (ISFD-6) - Nanjing, China|
Duration: 29 May 2000 → 2 Jun 2000
- Polar nanodomains
- Relaxor ferroelectrics
- Short-range order
- Synchrotron x-ray diffraction