Relaxing with relaxors: a review of relaxor ferroelectrics

Fano resonance and dipolar relaxation in lead-free relaxors

“…This controversial characteristic temperature T* therefore appears to be associated with a hardening of a very specific sublattice, namely the Ti sublattice. It will be interesting in the future to determine whether this is the case for other relaxors, since recent works seem to indicate that T* may have a different origin between lead-free and lead-based relaxors [33][34][35] .…”

“…Relaxor ferroelectrics also typically exhibit three characteristic temperatures, known as the Burns temperature T B , freezing temperature T f and the so-called T* (refs 2,3,4,23,24). While it is traditionally believed that T B is associated with the formation of dynamical PNRs and that T f corresponds to the temperature at which these PNRs become static, the precise microscopic origin of the third and intermediate critical temperature (that is T*) remains unclear and is intensively debated 24,[33][34][35] . Owing to their fundamental interest and also technological promise, relaxors have been studied by various techniques since their discoveries.…”

Phonon localization drives polar nanoregions in a relaxor ferroelectric

“…Recently, Swainson et al 17 found similar soft phonon columns near the zone edges in PMN ((Pb(Mg 1/3 Nb 2/3 )O 3 ) and attributed them to competing antiferroelectric distortions 17 . The extreme slow down of fluctuating PNRs on cooling has been explained in terms of quenched random electric fields 18,19 , but a connection to the lattice dynamics is unclear since the mass inertia of the polar displacements is not included in these models. Furthermore, Sherrington 20 recently suggested that since the dilution of the random field with increasing PT in PMN-xPT ((Pb(Mg 1/3 Nb 2/3 )O 3 ) 1 À x -(PbTiO 3 ) x ) does not decrease the relaxor onset temperature, random fields may play only a secondary role in relaxor behaviour.…”

Role of random electric fields in relaxors

“…These materials exhibit very low strain-electric field hysteresis, extremely large dielectric constants, and record-setting piezoelectric coefficients at room temperature that form an unusually appealing set of properties with the potential to revolutionize a myriad of important technological applications spanning medical diagnostic sonography, military sonar, energy harvesting, and high-precision actuators (6)(7)(8). Many researchers have argued that quenched random electric fields (REFs) play a central role in establishing the relaxor phase, in part because the B sites of all known leadoxide perovskite relaxors are occupied by random mixtures of heterovalent cations (9)(10)(11)(12)(13). However, there is ample theoretical work that suggests relaxor behavior can occur in the absence of REFs (14)(15)(16).…”