Nanoscale global mixed ordering of B-site cations in Pb<sub>2</sub>M′M′′O<sub>6</sub>complex perovskite relaxors

Baba-Kishi, K. Z.; Tai, Cheuk‐Wai; Meng, Xing

doi:10.1080/14786430600764880

Cited by 9 publications

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“…These findings are supported by the studies carried out by , suggesting that well ordered cation occupancies conflict with the notion of a 'space-charge' model and favour the 'random-site' model for the B-site long-range order. Long-range chemical clustering of B-site cations under certain conditions has been proposed to result in a specific superstructure in PST (Baba-Kishi et al, 2006). Positional displacements of the Pb ions on the A site are favoured by chemical ordering between Sc 3+ and Nb 5+ in PbSc 1/2 Nb 1/2 O 3 , as reported by Perrin et al (2001).…”

Section: Introductionmentioning

confidence: 79%

“…Most relaxors, including PbMg 1/3 Nb 2/3 O 3 (PMN) and PST, have a tendency to undergo structural evolution and may be viewed as adaptable structures (Withers et al, 1994). The structural evolution could include chemical long-range order of various degrees associated with a superstructure on the (111) planes and development of an additional superstructure associated with long-range clustering of B-site cations on the (100) planes in PST (Baba-Kishi et al, 2006). In addition, A-site and B-site displacements occur as a combined result of lone-pair electrons on Pb 2+ and the necessity of meeting the valence requirements by the Pb 2+ ions, e.g.…”

Section: Introductionmentioning

confidence: 99%

“…The 1:1 or 2:1 ideal columnar occupational stoichiometric ratio depends on whether the composition is 1:1, e.g. Long-range chemical clustering of B-site cations under certain conditions has been proposed to result in a specific superstructure in PST (Baba-Kishi et al, 2006). There is evidence suggesting that the larger of the B-site cations, B 0 , is ferroelectrically inactive and that the Pb ion is attracted to the larger cation (Chen et al, 1996).…”

Section: Introductionmentioning

confidence: 99%

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Direct observation ofB-site cation displacements in Pb-based complex perovskite relaxor oxides

Baba-Kishi

2010

J Appl Cryst

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Electron diffraction patterns recorded using a scanning transmission electron microscope (STEM) from PbMg1/3Nb2/3O3 (PMN) crystallites and PbZn1/3Nb2/3O3 (PZN) crystals show weak and systematic continuous diffuse streaking along the 〈110〉 directions. Detailed high‐angle annular dark‐field (HAADF) images recorded via an aberration‐corrected STEM show that the B‐site cations in PMN and PZN undergo correlated and long‐range displacements towards the Pb2+ ions on the (110) planes. The planar B‐site displacement measured from the centres of the octahedra is about 0.3–0.5 Å in PMN and about 0.20–0.4 Å in PZN. In the HAADF images of the PMN crystallites and PZN crystals studied, there is insufficient evidence for systematic long‐range planar displacements of the Pb2+ ions. The observed Pb2+ ion displacements in PMN and PZN appear randomly distributed, mostly displaced along 〈110〉 towards the B‐site columns. There is also evidence of possible stress‐related distortion in certain unit cells of PMN. In the relaxors studied, two distinct types of displacements were observed: one is the long‐range planar B‐site spatial displacement on the (110) planes, correlated with the Pb2+ ions, possibly resulting in the observed diffuse streaking; the other is short‐range Pb2+ ion displacement on the (110) planes. The observed displacement status indicates a mutual attraction between the Pb ions and the B‐site cations in which the B sites undergo the largest spatial displacements towards the Pb ions along 〈110〉.

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Section: Introductionmentioning

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Direct observation ofB-site cation displacements in Pb-based complex perovskite relaxor oxides

Baba-Kishi

2010

J Appl Cryst

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“…The transition is now sharp with no frequency dispersion of the dielectric response, 45 Previous studies using transmission electron microscopy have shown that structural modulations and complex strain pattern exist in all PST samples examined, independent of their degree of order. [46][47][48][49] These structural modulations are related to the relaxor behavior in disordered PST as PNRs. Structural modulations in ferroelectric PST also break the cubic symmetry at T > T trans so that polar behavior is observed in the nominally cubic phase.…”

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confidence: 99%

Ferroelectric precursor behavior of highly cation-ordered PbSc0.5Ta0.5O3 detected by acoustic emission: Tweed and polar nanoregions

Dul’kin¹,

Salje²,

Aktas³

et al. 2014

Applied Physics Letters

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Highly cation-ordered, ferroelectric PbSc 0.5 Ta 0.5 O 3 (PST) crystals have been studied by acoustic emission over a wide temperature range. The high degree of order leads to a non-dispersive dielectric anomaly at T trans = 300 K of a weakly first order phase transition. Acoustic emission (AE) was found at three characteristic temperatures, 330 K, 409 K and ∼600 K, but none between these temperatures. These temperatures are close to those known from cation-disordered relaxor PST, containing polar nano regions (PNRs). The microstructure in our ferroelectric PST contains structural tweed rather than PNRs. The coincidence of the AE temperatures points towards a close structural relationship between PNRs and tweed. Furthermore, when electric fields are applied, we observe shifts of these temperatures which are similar to 'critical end point' behavior. The similarity of AE signals in relaxors and tweed ferroelectrics proves that AE detects signals in a wider parameter space than previously expected.Random fields and local phase transitions are commonly evoked when symmetry changes in heterogeneous systems. While some models predict a well-defined transition behavior, such as the spherical random-bondrandom-field (SRBRF), 1,2 where the system transforms at a well-defined temperature from a paraelectric phase to a spherical glass phase without long range order. Other approaches predict smeared cross-overs such as Vugmeister and Rabitz, 3 and the traditional composition fluctuations model, 4 and the super-paraelectric model by Cross. 5 In none of these cases would a classic criticality analysis in terms of Wilson exponents of single thermodynamic order parameters be applicable. Experimentally, smeared crossovers are indeed seen in relaxor ferroelectrics (RFEs). These are materials with wide frequency dispersions of the dielectric response in the transition region. In addition, the transition between a paraelectric and a ferroelectric phase is not only smeared but also split into a number of other singularities which are commonly ascribed to the existence and temperature evolution of polar nanosized regions (PNRs), 6,7 The structural properties of PNRs are still not fully understood with few studies focused on atomic-level correlation effects between PNRs. 8Smooth crossover near the Burns temperature T d at high temperature range is seen in RFEs by the temperature evolution of the refractive index, 9-11 dielectrics and Brillouin light scattering, 12-19 polarized Raman spectra, 20,21 thermal expansion, 22-24 and acoustic emission (AE). 25-29 Similar behavior is found near the intermediate temperature T * . 12-21,30-35 On further cooling, a smeared frequency dependent temperature maximum of the dielectric response occurs near T m and, slightly below T m the freezing occurs at the freezing temperature T f , similar to polar-glass phases. [36][37][38][39] In contrast to these observations, one finds that AE studies [12][13][14][15][16][17][18][19]22,23,[25][26][27][28][29][30] show extremely sharp singularities at T d and T...

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“…Diffuse streaks along <110>* are observed in all major zone axes, indicating the presence of either planar defects or shortrange ordering along the directions. The ordered domains and the electrical properties of the ceramics suggest that the occurrence of diffuse streaks can be contributed by the large amount of short-range antiparallel polarization [5], polar nanoregions (PNRs) [6], various kind of nanoscale 1:1 ordering [4] and APBs. Relaxor behavior is given by the short-range polarization or polar nanoregions.…”

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confidence: 99%

Diffuse scattering in Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3 relaxor solid solutions

Tai¹

2013

Microsc Microanal

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Pb(In 1/2 Nb 1/2 )O 3 (PIN) and Pb(Mg 1/3 Nb 2/3 )O 3 (PMN) are complex perovskites with the chemical formula A(B' x B" 1-x )O 3 . The electrically balanced 1:1 B-site cation ordered domains, of which directions are along <111>, can form in PIN. In contrast, since the 1:2 stoichiometric cation ratio is the chemical nature of PMN. Antiferroelectricity and sharp phase transition can be observed in the highly ordered PIN; whereas the incompletely ordered and disordered PIN are relaxors, which exhibit diffuse phase transition and slim polarization hysteresis loop. Since the 1:1 order-disorder behaviour in PIN-PMN as well as other complex perovskite materials plays a central role in influencing the physical properties [1][2][3], TEM studies were carried out to investigate the various structural ordering. In addition to the superstructure reflection ½ ½ ½ given by 1:1 B-site ordering, the forbidden reflections ½ ½ 0 and diffuse streak and scattering are observed in selected-area electron diffraction (SAED) patterns, shown in Figure 2. The intensity of the features other than Bragg reflections depends on the composition of PIN, similar to the size of B-site ordered domains. The ½ ½ 0 reflections indicates that the crystal structure of the solid solutions have a lower symmetry than Fm-3m. Diffuse streaks along <110>* are observed in all major zone axes, indicating the presence of either planar defects or shortrange ordering along the directions. The ordered domains and the electrical properties of the ceramics suggest that the occurrence of diffuse streaks can be contributed by the large amount of short-range antiparallel polarization [5], polar nanoregions (PNRs) [6], various kind of nanoscale 1:1 ordering [4] and APBs. Relaxor behavior is given by the short-range polarization or polar nanoregions. The directions of the polarization can be in different crystallographic directions but still be stabilized and electrically balanced by the APBs. These are the consequence of three cations in the B-site and the source of random-field. However, the origin of these diffuse streak and scattering in SAED patterns is not fully understood [6,7].

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Nanoscale global mixed ordering of B-site cations in Pb₂M′M′′O₆complex perovskite relaxors

Cited by 9 publications

References 45 publications

Direct observation ofB-site cation displacements in Pb-based complex perovskite relaxor oxides

Direct observation ofB-site cation displacements in Pb-based complex perovskite relaxor oxides

Ferroelectric precursor behavior of highly cation-ordered PbSc0.5Ta0.5O3 detected by acoustic emission: Tweed and polar nanoregions

Diffuse scattering in Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3 relaxor solid solutions

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Nanoscale global mixed ordering of B-site cations in Pb2M′M′′O6complex perovskite relaxors

Cited by 9 publications

References 45 publications

Direct observation ofB-site cation displacements in Pb-based complex perovskite relaxor oxides

Direct observation ofB-site cation displacements in Pb-based complex perovskite relaxor oxides

Ferroelectric precursor behavior of highly cation-ordered PbSc0.5Ta0.5O3 detected by acoustic emission: Tweed and polar nanoregions

Diffuse scattering in Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3 relaxor solid solutions

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Nanoscale global mixed ordering of B-site cations in Pb₂M′M′′O₆complex perovskite relaxors