The antiferroelectric crystal structure of the highly ordered complex perovskite Pb(Yb1/2Nb1/2)O3

Abstract
The crystal structure of antiferroelectric Pb(Yb1/2Nb1/2)O3 has been characterized. Both X-ray diffraction and transmission electron diffraction show two sets of superlattice reflections originating respectively from the B-site atom ordering and the antiparallel lead-atom displacements which suffer within the orthorhombic ao-bo plane along the ao direction. The room-temperature crystal symmetry is considered to be orthorhombic with space group Pbnm (D2h16) and lattice parameters ao=5.918 AA, bo=23.453 AA and co=8.221 AA. High-resolution electron microscopy confirms the diffraction results. A structural phase transition from the lower-symmetry phase to the cubic paraelectric phase occurs at about 302 degrees C on heating.