X-ray and electron diffraction studies of the structures of pseudo-perovskite compounds Pb2(Sc,Ta)O6 and Pb2(Mg,W)O6

Abstract

Electron diffraction patterns, X-ray precession patterns and synchrotron Rietveld powder diffraction profiles were used to study the crystal structure of the pseudo-perovskite compound Pb2(Sc,Ta)O 6 (PST). The results of a Rietveld refinement and single-crystal X-ray precession studies showed that PST has a lower symmetry than the cubic Fm3m in the paraelectric state. The remarkable similarities between the crystal structures of the antiferroelectric Pb2(Mg, W)O 6 (PMW) and ferroelectric PST are studied in detail by electron diffraction and it is suggested that PST is a weak or frustrated antiferroelectric oxide. The influence of the degree of structural long-range order on the existence of an antiferroelectric phase transition in PST and PMW is discussed.

Transmission electron microscopy studies of Pb(Zr0.99Ti0.01)O3 single crystals

“…Diffuse scattering is clearly visible along the ͗110͘ c directions of the reciprocal space. This behavior seems to be very similar to that observed for Pb(Sc 0.5 Ta 0.5 )O 3 exhibiting ferroelectric relaxor properties [26,27]. In the case of Pb(Zr 0.99 Ti 0.01 )O 3 single crystals the diffuse scattering can be seen as precursor state of the antiferroelectric phase.…”

Characterization of (0.4)Pb2(In,Nb)O6:(0.6)Pb(Mg1/3Nb2/3)O3 relaxor ceramics

“…10 Recent studies by neutron diffraction show that these reflections can be allowed if the structure is considered rhombohedral with space group R3, indicating that the crystals of Pb 2 ScTaO 6 lack cubic symmetry in the paraelectric state. This reflection is often very difficult to record due its vanishing intensity.…”

“…[10][11][12][13] The structure of the relaxor Pb 2 ScTaO 6 has been refined from high-resolution neutron time-of-flight powder diffraction data at both 400 and 4.2 K. 11 In Pb 2 ScTaO 6 at 4.2 K, in the ferroelectric state, the structure is rhombohedral with a space group R3. [10][11][12][13] The structure of the relaxor Pb 2 ScTaO 6 has been refined from high-resolution neutron time-of-flight powder diffraction data at both 400 and 4.2 K. 11 In Pb 2 ScTaO 6 at 4.2 K, in the ferroelectric state, the structure is rhombohedral with a space group R3.…”

Structural transitions in Pb(In1∕2Nb1∕2)O3 under pressure

“…16,31,43 In addition, the coexistence of competing forces of ferroelectric and antiferroelectric forces may play a certain role in the formation of the relaxor state. 32,33,37,[44][45][46][47][48] We observe two type of diffuse scatterings, one is along reciprocal lattice lines, and the other one is butterfly shaped around Bragg peak. We show that both type of diffuse scattering are suppressed by pressure.…”