Relaxor ferroelectrics are materials with extraordinarily high electrostrictive constants. They are characterized by a diffuse phase transition, a giant dielectric permitivity, a strong piezoelectricity.
We consider here the perovskites Pb(Zn1/3Nb2/3)O3 (PZN) and Pb(Mg1/3Nb2/3)O3 (PMN) and their solid solutions with PbTiO3. They have an average ABO3 perovskite structure perturbed by occupational disorder on B-site positions.
FlatCone made it possible to examine both there "waterfall" anomaly and elastic diffuse scattering at several temperatures.
One of the characteristic features of the lattice dynamics of relaxor ferroelectrics is the so-called "Waterfall" anomaly with apparent vertical dispersion of low lying acoustic/optic phonon branches, first observed in the PZN-8%PT system by P. M. Gehring, S. E. Park & G. Shirane, Phys. Rev. Lett. 84 (2000) 5216.
The existence of an analogous feature in the PMN system has been subject to controversial discussion, but the FlatCone data provide an evidence for it.
The flat-cone geometry with the tilted multianalyzer configuration permits systematic investigation of superlattice peaks having a momentum offset with respect to the equatorial plane. The (h k 0.5) plane displays two famillies of correlations: the <0.5 0.5 0.5> exhibiting more static features (presumably due to chemical short-range order) and the <0.5 0.5 0 > appearing only at lower temperatures and exhibiting a strong inelastic componenets and a temperature dependence close to the relaxor order parameter.
FlatCone made it possible to measure the integrated intensity of the two types of satellites in the temperature range 4 K to 1100 K.