Compositional disorder, polar nanoregions and dipole dynamics in Pb(Mg_1/3Nb_2/3)O₃-based relaxor ferroelectrics

Abstract

The complex structure of relaxor ferroelectrics comprises polar nanoregions (PNRs) which appear upon cooling below the Burns temperature and quenched compositional (chemical) disorder. The relation between the polar nanostructure and compositionally ordered regions (CORs) often observed in relaxors has been the subject of extensive theoretical investigations; however, the experimental data, especially concerning Pb(B′1/ 3B″2/3)O3-type complex perovskite relaxors, are rather limited. In this paper, we analyse and discuss the results of our recent investigations of the morphology of CORs and the dynamics of PNRs in Pb(Mg1/ 3Nb2/3)O3 based solid solutions in which the degree of compositional disorder was varied by means of changing the composition and/or by means of high-temperature annealing. The samples were characterised using X-ray diffraction, transmission electron microscopy, piezoresponse force microscopy, Brillouin light scattering, dielectric spectroscopy, as well as by measuring pyroelectric effect and ferroelectric hysteresis loops. No influence of the size of CORs on the PNRs relaxation in the ergodic relaxor phase is found. Instead, the CORs size influences significantly the diffuseness of the transition from the field-induced ferroelectric phase to the ergodic relaxor state. The results are interpreted in the framework of a model suggesting the coexistence of static and dynamic PNRs in the ergodic relaxor phase. Relaxor ferroelectrics / Compositional disorder / Lead magnesium niobate / Dielectric relaxation / Domain structure Abstract. The complex structure of relaxor ferroelectrics comprises polar nanoregions (PNRs) which appear upon cooling below the Burns temperature and quenched compositional (chemical) disorder. The relation between the polar nanostructure and compositionally ordered regions (CORs) often observed in relaxors has been the subject of extensive theoretical investigations; however, the experimental data, especially concerning Pb(B 0 1=3 B 00 2=3 )O 3 -type complex perovskite relaxors, are rather limited. In this paper, we analyse and discuss the results of our recent investigations of the morphology of CORs and the dynamics of PNRs in Pb(Mg 1/3 Nb 2/3 )O 3 -based solid solutions in which the degree of compositional disorder was varied by means of changing the composition and/or by means of high-temperature annealing. The samples were characterised using X-ray diffraction, transmission electron microscopy, piezoresponse force microscopy, Brillouin light scattering, dielectric spectroscopy, as well as by measuring pyroelectric effect and ferroelectric hysteresis loops. No influence of the size of CORs on the PNRs relaxation in the ergodic relaxor phase is found. Instead, the CORs size influences significantly the diffuseness of the transition from the field-induced ferroelectric phase to the ergodic relaxor state. The results are interpreted in the framework of a model suggesting the coexistence of static and dynamic PNRs in the ergodic relaxor phase.

Electrocaloric properties in relaxor ferroelectric (1−x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 system

“…It seems that the occurrence of static PNRs is closely related to the presence of chemically ordered regions (CORs). 33 Therefore, as the size of CORs is known to be decreased in PMN-xPT with increasing x, 34 it is believed that static PNRs behave in a similar way. From this viewpoint, the PMN-xPT composition with lower x has an increased difficulty for field-induced PNR growth in the ergodic phase due to a higher number of constrained PNRs (both dynamic and static).…”

Static and dynamic polar nanoregions in relaxor ferroelectric Ba(Ti1−xSnx)O3Xie1, Li2, Yu3 et al. 2012Phys. Rev. B802260View full textAdd to dashboardCite

“…Recent experiments by using switching spectroscopy piezoresponse force microscopy reported the presence of a mesoscopic static PNRs structure in PMN-10PT. 37 Using neutron scattering techniques, it was found in PMN that static PNRs with at least 2 ns lifetime are formed below the Burns temperature. 38 These static PNRs are suggested to be pinned by local chemical order inside the chemically ordered regions.…”

Structural analysis of lead magnesium niobate using synchrotron powder X-ray diffraction and the Rietveld method

“…The exact nature and explanations of these properties are still unresolved. The present understanding of relaxor behavior is based on the multiple inhomogeneities/disorder present in these systems (Fu et al, 2009;Bokov et al, 2011). PMN has perovskite structure (ABO 3 -type) in which Pb 2+ occupy the 'A' site and the 'B' site is occupied by Mg 2+ /Nb 5+ ions.…”