Order and disorder in the relaxor ferroelectric perovskite (PSN): comparison with simple perovskites and

Abstract

We report a structural evolution analysis of the long-range and local order and disorder of lead scandium niobate (PSN) down to 10 K, using a combination of neutron and x-ray diffraction on powder and single crystals. The structure of PSN is discussed and compared with those of simple perovskite compounds and . In PSN the existence of a long-range but still disordered ferroelectric phase, different from those of simple perovskites, is evidenced. The disorder of lead and scandium/niobium atoms on short-, medium- and long-range scales is discussed in connection with the dielectric properties of these materials.

Role of random electric fields in relaxors

“…To answer these questions we compared the nanoscale structures of PMN and PZT using neutron-based measurements of the elastic diffuse scattering, which is arguably the single most interesting and intensely examined property of lead-oxide relaxors to date. Strong, temperaturedependent and highly anisotropic diffuse scattering has been documented in many different lead-oxide perovskite relaxors using X-ray and neutron-scattering methods (20)(21)(22)(23)(24)(25)(26)(27). Fig.…”

Brillouin scattering studies of acoustic phonon modes and central peak in single-crystal Pb(Sc1/2Ta1/2)OSivasubramanian1, Kojima2 2012Phys. Rev. B

“…Normal ferroelectric state in PST is characterized by long-range ferroelectric order with nonvanishing macroscopic spontaneous polarization ( P = 0) along 111 direction. 12 In this case, one would expect the first term, i.e., bilinear coupling, linear in order parameter (polarization) and strain to be the dominant term in the coupling free energy F c . Therefore the sharp damping maximum for the LA phonon at 295 K can evidently be connected with the Landau-Khalatnikov-like relaxation mechanism, which is associated with the bilinear coupling.…”

“…10 A spontaneous relaxor-to-ferroelectric phase transition accompanied by a change in the structure from cubic to rhombohedral below T m , the temperature of maximum dielectric constant has also been observed in these systems. [11][12][13] Raman and IR spectroscopic studies of PST showed the increase in intensity and narrowing of the width of the phonon modes with increase in B-site chemical ordering. 14,15 The presence of Pb vacancies also strongly influences the structural and dielectric behavior of PST.…”

Strain Mechanisms in Lead-Free Ferroelectrics for Actuators

“…64 These PNRs can be regarded as clusters on the order of 10 nm composed of thermally activated dipolar entities that originate from local deviations in crystal structure and/or chemical heterogeneities in the A-and/or B-site cation sublattices. [80][81][82][83][84] Several attempts have been made to rationalize relaxors within one theoretical model. However, so far no general agreement in their microscopic picture has been achieved.…”