Structural Heterogeneity and Diffuse Scattering in Morphotropic Lead Zirconate-Titanate Single Crystals

Abstract

Complementary diffuse and inelastic synchrotron x-ray scattering measurements of lead zirconate-titanate single crystals with composition near the morphotropic phase boundary (x=0.475) are reported. In the temperature range 293 K<T<400 K a highly anisotropic quasielastic diffuse scattering is observed. Above 400 K this scattering disappears. Its main features can be reproduced by the model of inhomogeneous lattice deformations caused by inclusions of a tetragonal phase into a rhombohedral or monoclinic phase. This observation supports the idea that PZT at its morphotropic phase boundary is essentially structurally inhomogeneous.

Role of random electric fields in relaxors

“…S1). Static diffuse scattering was recently reported in a single crystal of PZT with x = 0:475 using X-ray inelastic scattering techniques (41). However, these data were obtained with an energy resolution nearly 10 times coarser than ours; hence there is a possibility of phonon contamination.…”

The missing boundary in the phase diagram of PbZr1−xTixO3

“…However, although there has been some published work regarding the real local structures of PZT [30][31][32][33][34][35] , most lack a thorough analysis of the role of the Pb atoms in the MPB area. Here, PDF analyses of PZT compositions with x ¼ 0.2, 0.3 and 0.4 are presented and a re-examination of earlier Rietveld results show that the displacements of the Pb atoms undergo a composition-enforced change between two monoclinic variants, thus revealing a monoclinic-monoclinic boundary (crossover) for the first time.…”

Confirmation of the monoclinic Cc space group for the ground state phase of Pb(Zr0.525Ti0.475)O3: A combined synchrotron X-ray and neutron powder diffraction study

“…However some authors reported that the true ground state of PZT in and around the MPB is rhombohedral in the R3c space group and it coexists with the monoclinic phase in Cm space group over a wide composition range [14][15][16][17][18][19][20] . Thus the true symmetry of the low temperature phase of PZT has become controversial as evidenced by several recent publications on this system [17][18][19][20][21][22][23] . The main objection against the Cc space group is the non-observation of the (1/2 1/2 1/2) pc (pc stands for pseudocubic indices) superlattice peak which is permitted by the Cc space group but is extinguished in the R3c space group.…”

“…The existence of the low-temperature superlattice phase in the Cc space group was confirmed by other workers also in their transmission electron microscopy (TEM) 11,12 and neutron powder diffraction studies as a function of temperature 10,13 and pressure 13 and was nearly accepted as the true ground state of PZT. However some authors reported that the true ground state of PZT in and around the MPB is rhombohedral in the R3c space group and it coexists with the monoclinic phase in Cm space group over a wide composition range [14][15][16][17][18][19][20] . Thus the true symmetry of the low temperature phase of PZT has become controversial as evidenced by several recent publications on this system [17][18][19][20][21][22][23] .…”

“…The value of χ 2 dropped from 6.74 for R3m space group to 1.75 for the Cm space group. We also considered the possibility of 7 coexisting R3c phase (which becomes R3m in the absence of superlattice peaks) along with Cm phase as proposed by several authors [14][15][16][17][18][19][20] for the ground state of PZT.Refinement using R3m+Cm coexisting model was carried out in three different ways.Firstly, we add a coexisting Cm phase to the refined structure obtained using single phase R3m space group. The value of χ 2 reduced drastically (from 6.74 to 1.73) and the Rietveld fit improved.…”