Favorable Concurrence of Static and Dynamic Phenomena at the Morphotropic Phase Boundary of xBiNi0.5Zr0.5O3<

Abstract

We reveal that concurrent events of inherent entropy boosting and increased synchronization between A- and B-site cation vibrations of an ABO_{3}-type perovskite structure give rise to a larger piezoelectric response in a ferroelectric system at its morphotropic phase boundary (MPB). It is further evident that the superior piezoelectric properties of xBiNi_{0.5}Zr_{0.5}O_{3}-(1-x)PbTiO_{3} in comparison to xBiNi_{0.5}Ti_{0.5}O_{3}-(1-x)PbTiO_{3} are due to the absolute flattening of the local potentials for all ferroelectrically active cations with a higher spontaneous polarization at the MPB. These distinctive features are discovered from the analyses of neutron pair distribution functions and Raman scattering data at ambient conditions, which are particularly sensitive to mesoscopic-scale structural correlations. Altogether this uncovers more fundamental structure-property connections for ferroelectric systems exhibiting a MPB, and thereby has a critical impact in contriving efficient novel materials.

High electromechanical response in the non morphotropic phase boundary piezoelectric system PbTiO3−Bi(Zr1/2Ni1Pandey1, Narayan2, Khatua3 et al. 2018Phys. Rev. B302110View full textAdd to dashboardCite

“…This view may also be emboldened by the fact that a related system (1-x)PbTiO3-(x)BiScO3 (PT-BS) shows clear evidence of rhombohedral distortion (the splitting of pseudo-cubic {111}pc Bragg profile into two) on the global scale on the BS excess side of the MPB region [5,21]. A recent neutron pair distribution function analysis of unpoled (1-x)PT-(x)BNZ by Datta et al [53] revealed a gradual change in the local structure from tetragonal to non-tetragonal with increasing composition (x). By comparing their results with those reported earlier for rhombohedral/monoclinic compositions of the PT-BS system [54], the authors argued in favour of the presence of MPB in PT-BNZ.…”

Distinct temperature behavior of the local structure of (1‐x)PbTiO3‐xBiNi0.5Ti0.5O3 at the morphotropic phase boundary

“…The x ‐dependencies of the mode wavenumbers indicate multistep composition‐induced transformations at room temperature: (a) the initial incorporation of BNiT ( x =0.1) increases the anisotropy of the A‐site local potentials by introducing a new lower‐energy state (Figure C); (b) the anisotropy in the local potentials in the subsystem of off‐centered B‐site cations gradually decreases upon BNiT doping and diminishes at x =0.50< x MPB (Figure D), where the A‐cation‐localized ETO1 mode shows a pronounced minimum in wavenumber (Figure C) indicating coupling processes within the A‐cation subsystem; and (c) at the MPB composition, the A‐BO 3 mode that corresponds to the quasi‐TO1(A 1 +E) excitation in PT‐based ceramics softens and broadens (Figure B), revealing coupling between the adjacent local dipoles at the A and B sites, that is, between the sublattices of off‐centered A‐site and B‐site cations, a phenomenon that appears to be universal for perovskite‐type ferroelectric solid solutions with MPB . All together, this indicates that at room temperature, the composition‐induced local‐scale rearrangements within the A‐cation subsystem as well as within the B‐cation subsystem occur slightly below the MPB, which probably facilitates the change of the ferroelectric long‐range order at the MPB.…”

“…Commercially available PbTiO 3 powder from Sigma‐Aldrich with a purity of 99.9 % was used as a reference undoped material. The chemical compositions of the samples were verified by wavelength‐dispersive electron microprobe analysis using a Cameca Microbeam SX100 system . The room‐temperature unit‐cell parameters were derived from powder XRD patterns collected with a STOE STADI‐MP diffractometer in Bragg‐Brentano geometry over a 2 θ ‐range of 20° to 90°.…”

“…The chemical compositions of the samples were verified by wavelength-dispersive electron microprobe analysis using a Cameca Microbeam SX100 system. [24] The room-temperature unit-cell parameters were derived from powder XRD patterns collected with a STOE STADI-MP diffractometer in Bragg-Brentano geometry over a 2 -range of 20 • to 90 • . The sharpness of the Bragg peaks indicated negligible defect-related intrinsic strains and a relatively large mean size of the crystallites, which, according to the Scherrer equation, was above 180 nm for all samples.…”

“…[21,22] Nowadays, it is widely accepted that a single or multiple phases of low symmetry (monoclinic, triclinic, orthorhombic) exist at the MPB, acting as a structural bridge between the tetragonal and rhombohedral/pseudorhombohedral phases in a solid solution and allowing for easy rotation of the unit-cell polarization. [6,23] Recent studies have, however, emphasized the importance of the mesoscopic-scale structure for the composition-driven property enhancement at room temperature, revealing that at the MPB, the dispersion of local atomic surroundings of the A-and B-site cations is enlarged, [24,25] which facilitates the flattening of the energetic barrier between the different types of ferroelectric long-range order and the optimal domain reorientation during the poling process. Moreover, very recent studies of the high-temperature state of pure PT indicate multistep coupling processes of local ferroic distortions occurring already above T C [9] and imply that the MPB in PT-based solid solutions is a chemically stabilized temperature-independent ergodic state of locally synchronized dipoles.…”