The relation of local order to material properties in relaxor ferroelectrics

Krogstad, Matthew; Gehring, P. M.; Rosenkranz, S.; Osborn, R.; Ye, Feng; Liu, Yaohua; Ruff, Jacob P. C.; Chen, Wenzhi; Wozniak, Justin M.; Luo, Haosu; Chmaissem, O.; Ye, Zuo‐Guang; Phelan, Daniel

doi:10.1038/s41563-018-0112-7

Cited by 131 publications

(137 citation statements)

References 53 publications

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“…To visualize the effect of strain on the diffuse-scattering, the data are represented as iso-intensity contours using cutoff intensities that effectively represent the diffuse-scattering shape for different strain states, and variations are clearly visible. For comparison with the literature, where the diffuse-scattering is usually reported in two-dimensional representations, [10][11][12][13][14][15][16][17][18][19] data for the 0kl plane which cuts through the primary Bragg reflections (shaded plane, Figure 1c-e) are also provided (Figure 1f Figure S3a, Supporting Information), confirming important features of the diffuse-scattering of single-crystal relaxors [13] and that such films can serve as a reference for further discussions of strain-induced effects. Inspection of intermediate-strain heterostructures (Figure 1d,g) reveals that the butterfly-shaped diffuse-scattering has evolved into a discshaped pattern.…”

supporting

confidence: 58%

Epitaxial Strain Control of Relaxor Ferroelectric Phase Evolution

Kim

Takenaka

et al. 2019

Advanced Materials

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Alternatively, molecular-dynamics (MD) simulations have shown that relaxors can be interpreted as exhibiting a multidomain state without a nonpolar matrix (i.e., polar nanodomains or PNDs). [4] The exact nature of order in relaxors, however, remains an ongoing debate [5] and, in turn, new approaches to study these complex materials are required to further illuminate the structure and how it can be controlled and can impact material properties. [5-9] In any case, it is essential to understand the evolution of the polar structure in relaxors (be they PNRs or PNDs) under applied stimuli as these are key to understanding relaxor behavior and large electromechanical effects in relaxors. Over the years, X-ray and neutron diffuse-scattering measurements have emerged as an essential tool to study the structural signatures of relaxor behavior [10-19] and studies on single-crystal relaxors have investigated the evolution of polar regions/domains (e.g., size, morphology) and suggested that they alter their size [14-17] and orientation [18] under different external stimuli. For example, under applied electric fields, which were expected to enhance polar order, the local order was found to align perpendicular to the field [18] and induce an asymmetry in the lattice dynamics [19] that could ultimately be responsible for the large electromechanical effects. [20] Other studies used pressure to push the material in the opposite directionto destabilize polar order [17]-and even induce a crossover from Understanding and ultimately controlling the large electromechanical effects in relaxor ferroelectrics requires intimate knowledge of how the local-polar order evolves under applied stimuli. Here, the biaxial-strain-induced evolution of and correlations between polar structures and properties in epitaxial films of the prototypical relaxor ferroelectric 0.68PbMg 1/3 Nb 2/3 O 3-0.32PbTiO 3 are investigated. X-ray diffuse-scattering studies reveal an evolution from a butterfly-to disc-shaped pattern and an increase in the correlation-length from ≈8 to ≈25 nm with increasing compressive strain. Molecular-dynamics simulations reveal the origin of the changes in the diffuse-scattering patterns and that strain induces polarization rotation and the merging of the polar order. As the magnitude of the strain is increased, relaxor behavior is gradually suppressed but is not fully quenched. Analysis of the dynamic evolution of dipole alignment in the simulations reveals that, while, for most unit-cell chemistries and configurations, strain drives a tendency toward more ferroelectric-like order, there are certain unit cells that become more disordered under strain, resulting in stronger competition between ordered and disordered regions and enhanced overall susceptibilities. Ultimately, this implies that deterministic creation of specific local chemical configurations could be an effective way to enhance relaxor performance.

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confidence: 58%

Epitaxial Strain Control of Relaxor Ferroelectric Phase Evolution

Kim

Takenaka

et al. 2019

Advanced Materials

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“…heterogeneity, which could break the long-range ordered polar states and promote the formation of polar nanoregions (PNRs). [10][11][12][13][14][15] The PNRs have been confirmed in many materials, and considered to be closely related to the excellent piezoelectric properties and dielectric relaxation behavior. 16,17 For the PIMNT system, the introduction of In 3+ cation in the PMNT system will increase the disorder of B-site ions, which should lead to different dielectric relaxation characteristics from that of the PMNT system.…”

Section: Introductionmentioning

confidence: 95%

“…In relaxor‐based ferroelectric solid solutions, the competition between order‐disorder of B‐site cations and the local random fields are thought to result in the local structural heterogeneity, which could break the long‐range ordered polar states and promote the formation of polar nanoregions (PNRs) . The PNRs have been confirmed in many materials, and considered to be closely related to the excellent piezoelectric properties and dielectric relaxation behavior .…”

Section: Introductionmentioning

confidence: 99%

Dielectric relaxation and local domain structures of ferroelectric PIMNT and PMNT single crystals

Sun

et al. 2019

J Am Ceram Soc

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Dielectric relaxation properties of ternary Pb(In1/2Nb1/2)O3‐0.49Pb(Mg1/3Nb2/3)O3‐0.27PbTiO3 (PIMNT27) and binary Pb(Mg1/3Nb2/3)O3‐0.27PbTiO3 (PMNT27) single crystals have been investigated. The dielectric constant peak temperature Tm with frequency obeys the Vogel‐Fulcher (V‐F) law. The dielectric constants at temperatures above Tm can be described by the Lorenz‐type relationship. The fitting parameter δA and ΔTm of PIMNT27 are higher than those of PMNT27, indicating stronger relaxation in ternary PIMNT system. Local nanodomain structures were measured by the piezoelectric force microscopy (PFM). The average autocorrelation function technique was applied to quantify these nanoscale domain patterns. The PIMNT27 exhibits smaller size nanodomains and shorter mean local short‐range correlation length compared to PMNT27. The enhanced local disorder in PIMNT is related to the introduction of In3+ in PMNT system, which can enhance the disorder of B‐site ions. In addition, the evolution of local polarization rotation under a step‐increased tip dc voltage and the mean local short‐range correlation length <ξ> as a function of dc voltage were obtained for both PIMNT27 and PMNT27 single crystals, which are crucial parameters for the understanding of the relationship between dielectric relaxation and local domain structures in relaxor‐PbTiO3 systems.

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“…is not well defined so far 52,53 . The experimental results show that the systems with definite components but adjustable ion distributions, such as PbSc 1/2 Ta 1/2 O 3 , continuously evolve from normal-ferroelectrics to RFEs with the increase of disorder 14 , so it looks reasonable that the random distribution of ions, i.e.…”

Section: Definition Of Canonical Rfes Pmn Is Generally Viewed As Thementioning

confidence: 97%

Theory of relaxor-ferroelectricity

Zhang

Huang

2020

Sci Rep

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Relaxor-ferroelectrics are fascinating and useful materials, but the mechanism of relaxor-ferroelectricity has been puzzling the scientific community for more than 65 years. Here, a theory of relaxorferroelectricity is presented based on 3-dimensional-extended-random-site-Ising-model along with Glauber-dynamics of pseudospins. We propose a new mean-field of pseudospin-strings to solve this kinetic model. The theoretical results show that, with decreasing pseudospin concentration, there are evolutions from normal-ferroelectrics to relaxor-ferroelectrics to paraelectrics, especially indicating by the crossovers from, (a) the sharp to diffuse change at the phase-transition temperature to disappearance in the whole temperature range of order-parameter, and (b) the power-law to Vogel-Fulcher-law to Arrheniusrelation of the average relaxation time. Particularly, the calculated local-order-parameter of the relaxorferroelectrics gives the polar-nano-regions appearing far above the diffuse-phase-transition and shows the quasi-fractal characteristic near and below the transition temperature. We also provide a new mechanism of Burns-transformation which stems from not only the polar-nano-regions but also the correlationfunction between pseudospins, and put forward a definition of the canonical relaxor-ferroelectrics. The theory accounts for the main facts of relaxor-ferroelectricity, and in addition gives a good quantitative agreement with the experimental results of the order-parameter, specific-heat, high-frequency permittivity, and Burns-transformation of lead magnesium niobate, the canonical relaxor-ferroelectric. 65 years after the discovery of so-called relaxor-ferroelectrics (RFEs) 1 , this manuscript promises to deliver the still missing theory of relaxor-ferroelectricity [Supplementary Information (SI) 1] 2-10 . For the existing phase-transition theories of normal-ferroelectrics are based on both structure and component homogeneity [11][12][13] , theoretically, the main difficulty in describing relaxor-ferroelectricity originates from RFEs being component-disordered although structure-ordered, i.e. disordered components on crystal lattices [14][15][16][17][18][19] . In fact, understanding how the component disorder on lattices leads to novel properties is an outstanding scientific challenge for a broad class of materials that include not only RFEs, but also spin glasses 20 , superelastic strain glasses (shape-memory alloys) 21 , colossal magnetoresistance manganites, and some superconductors 22 .The best-known member of the RFE family is the disordered perovskite crystal PbMg 1/3 Nb 2/3 O 3 (PMN), for which 27 years ago a plausible interpretation of its diffuse-phase-transition (DPT) was proposed by Westphal et al. 3 . Fluctuations of random-internal-electric-field (RIEF) emerging from the quenched charge disorder of the RFE are stabilizing the typical disordered polar nanodomain state. This disordering mechanism convinced sceptical experts at the latest thanks to a favorable review of Cowley et al. 16 . The subseq...

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The relation of local order to material properties in relaxor ferroelectrics

Cited by 131 publications

References 53 publications

Epitaxial Strain Control of Relaxor Ferroelectric Phase Evolution

Epitaxial Strain Control of Relaxor Ferroelectric Phase Evolution

Dielectric relaxation and local domain structures of ferroelectric PIMNT and PMNT single crystals

Theory of relaxor-ferroelectricity

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