Incommensurately modulated structures in Zr-rich PZT: periodic

3 Jul 2018 - Crystal Growth & Design · Advanced .... modulated structures in Zr-rich PZT: periodic nanodomains, reciprocal configuration and nucleatio...
0 downloads 0 Views 3MB Size
Subscriber access provided by TUFTS UNIV

Article

Incommensurately modulated structures in Zr-rich PZT: periodic nanodomains, reciprocal configuration and nucleation Zhengqian Fu, Xuefeng Chen, Ping Lu, Chenxi Zhu, Henchang Nie, FangFang Xu, Genshui Wang, and Xianlin Dong Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.8b00369 • Publication Date (Web): 03 Jul 2018 Downloaded from http://pubs.acs.org on July 7, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Crystal Growth & Design

Incommensurately modulated structures in Zr-rich PZT: periodic nanodomains, reciprocal configuration and nucleation Zhengqian Fu a,c,d 1, Xuefeng Chen Wang b * and Xianlin Dong b,d, *

b1

, Ping Lu a, c, Chenxi Zhu a, c Henchang Nie b, Fangfang Xu, a,c,d, *, Genshui

a

State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China. b The Key Lab of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China. c Analysis and Testing Center for Inorganic Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China. d School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China.

Abstract: Zr-rich PZT is one of the most representative materials with compositions located at ferroelectric-antiferroelectric (FE-AFE) phase boundary. The study of its incommensurately modulated structure (IMS) is of fundamental importance in understanding the origin of its high-performance stored-energy properties and phase transformation between FE and AFE. In this study, the structural features of the IMS were investigated in details by TEM. The IMS appears as submicron domains assembled by periodic arrays of two-dimensional nanodomains along a direction with the domain width of about 30 {111} spacings. The nanodomains have dual attributes of both antiphase domains and electric domains. The displacement vector across the periodic antiphase boundaries was determined to be R = [001]. The reciprocal lattice of IMS was constructed and characterized by a set of strong basic reflections of pseudo-cubic unit cell together with 1/2{ooe} superlattice reflections where 1/2(ooe) superlattice reflections (located on the (001) reciprocal planes) do not split while both 1/2(eoo) and 1/2(oeo) superlattice reflections (located on (100) and (010) reciprocal planes, respectively) split. In addition, the growth process of IMS and the visibility conditions for the periodic nanodomains and superlattice reflections splitting were presented.

Keywords: FE-AFE boundary, incommensurately modulated structure, antiphase domain, periodic nanodomain, Zr-rich PZT 1 These authors contributed equally to this work

ACS Paragon Plus Environment

Crystal Growth & Design 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1. INTRODUCTION Ferroelectric-antiferroelectric (FE-AFE) phase boundary separates two different types of polarization ordering state, i.e. parallel and antiparallel arrangement of dipoles, respectively.1-4 The parallel dipoles make FE materials find wide applications in microelectronics, memory, medical diagnostics and automobile industry etc.5 The transformation between parallel and antiparallel dipoles state makes AFE act as enabling technology in high energy storage capacitors, micro-actuators, pyroelectric security sensors, cooling devices, and pulsed power generators etc.6 One of the most representative materials with composition located at FE-AFE phase boundary is Zr-rich PZT.3,7 At the left compositional side of FE-AFE boundary, Pb cations displace antiparallel along [110]p/[ 11 0]p (the subscript “p” refers to pseudocubic unit cell) directions and this displacement is coupled with a-a-c0 octahedra tilt system, giving a 4ap x 4bp x 2cp supercell.8,9 At the right compositional side of FE-AFE boundary, the structure is characterized by long-range monoclinic symmetry involving [uuv]p displacement of Pb and average rhombohedral symmetry with p displacement of Pb, which can be described in terms of short-range order monoclinic symmetry and octahedral tilts.10-16 As for composition located at FE-AFE boundary itself, the structure and microstructure often present a complex picture. Appearance of incommensurately modulated structure (IMS) is the representative example of the complex structure, which was understood as a result of competing interactions between antiferroelectric and ferroelectric orderings.17-19 The IMS was firstly observed by Viehland et al., whose feature was characterized by splitting of reflections at 1/2{ooe} (o means odd and e means even) positions in electron diffraction patterns.20,21 Then Ricote et al. gave pictures of the IMS in real space using dark-field imaging and speculated the nanosized modulated structure as periodic antiphase boundaries (APB).21 After that, the modulation mode of the IMS was discussed by Watanabe et al.23,24 These investigations have revealed some features of the IMS in Zr-rich PZT, whereas the detailed crystallographic information, associated morphology in real space, nature of the IMS and growth process are still missing. Prior to further understanding of the unique properties arising at the FE-AFE boundary and phase transformation between FE and AFE, these informations should be clarified preferentially. Aiming at this, in the present study we performed in-depth structural investigations of PZT ceramics with composition located at FE-AFE boundary by select-area electron diffraction (SAED), dark-field (DF) imaging and high resolution electron microscopy (HREM) in transmission electron microscope (TEM).

2. EXPERIMENTAL SECTION Zr-rich PZT ceramics with composition located at FE-AFE boundary were prepared by solid-state reaction sintering and the designed compositions were Pb(Zr0.97Ti0.03)O3 + 1 wt.%Nb2O5 (PZT973). Adding small amount of Nb is a customary way to stabilize the FE phase at ambient conditions and to reduce dielectric losses. The starting raw materials used were Pb3O4 of 99.26% purity, TiO2 of 99.38% purity, ZrO2 of 99.99% purity and Nb2O5 of 99.86% purity, whereas 0.5 wt% of Pb3O4 excess amount was added in compensation of the volatilization during sintering. These oxide powders were mixed and calcined at 850 °C for 2 h. After fine milling, some disks were pressed and sintered at 1300 °C for 1 h. The transmission electron microscope investigation was carried out on a JEOL 2100F operated

ACS Paragon Plus Environment

Page 2 of 15

Page 3 of 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Crystal Growth & Design

at 200 kV. TEM specimens were prepared by a conventional approach combining mechanical thinning and finally Ar+ milling in a Gatan PIPSⅡat 3kev. Specimens were then coated with a thin layer of carbon to minimize charging under the electron beams. Some of TEM specimens were heat treated at 500 °C for 30 min. Consistent results observed in both specimen with and without heat treatment excluded the possibility of IMS formation by TEM specimen preparation processes (Fig. S4).

3. RESULTS AND DISCUSSION 3.1 Morphologies of the IMS. All crystallographic directions and planes refer to the simple pseudo-cubic unit cell in this study. Figure 1 shows the representative morphologies of the IMS, which were acquired by DF imaging using a 1/2{110} superlattice reflection. When viewed along zone axis, submicron domains separated by irregular shaped antiphase boundaries (APBIS) can be observed (Fig. 1a), which were identical to those reported by Ricote et al.21 When viewed along zone axis, a periodic array of parallel dark and bright stripes were visible with a spacing of about 4 nm (nanodomains). These parallel nanodomains coexist with APBIS and may curve by 180° at the APBIS (Fig. 1b). Sole parallel stripes covering the whole large grain can also be frequently observed (Fig. S1). In fact, the submicron antiphase domains are assembled by nanodomains whose visibility depends on the reflections used for DF imaging and viewing direction.

ACS Paragon Plus Environment

Crystal Growth & Design 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

FIG. 1. Dark-field images using the 1/2{110} superlattice reflections showing representative morphologies of the IMS in PZT97/3. (a) Viewing along direction: submicron domains are observed being separated by irregular shaped APB. (b) Viewing along direction: periodic nanosized domains are observed coexisting with irregular shaped APB. Corresponding SAED patterns are inserted at left bottom of dark-field images. The magnified image inserted at right top of (b) shows nanosized domain boundaries turn 180° at an irregular shaped APB.

The SAED pattern (Fig. 2a) revealed the reciprocal space feature of the IMS where the 1/2{ooe} superlattice reflections split to form two satellite spots in a direction along [111] on the [101] zone axis diffraction pattern. Appearance of the 1/2{ooe} superlattice reflections could be due to either in-phase rotations of octahedra or antiparallel displacements of the cations, which still remains controversial. The DF images using these split reflections gave the real space feature of the IMS showing a periodic array of parallel nanodomains which are aligned perpendicular to the splitting

ACS Paragon Plus Environment

Page 4 of 15

Page 5 of 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Crystal Growth & Design

direction with a real space periodicity inversely related to the splitting width in the reciprocal space (Fig. 2b). HREM image (Fig. 2c) indicates the parallel nanodomains are antiphase domains in which the lattice fringes in two adjacent domains mutually shift by half of the supperlattice vector similar to the famous periodic APB in CuAuⅡ.24 Consistent to the split reflections in Fig. 2a, the periodic APB approximately locate on the (111) plane as again evidenced in this edge-on HREM image. Therefore, the IMS shows a long-period ordering along a direction with a periodicity of about 30 {111} spacings. Surprisingly, DF image using a basic reflection (Fig. 2d) also exhibits the same periodic array of stripes but with faint contrast. Therefore, it appears that the parallel nanodomains are not only antiphase domains but also ferroelectric or antiferroelectric domains. Unfortunately, the exact atomic structures in these nanodomains including polarization direction and associated ferroelectricity or antiferroelectricity are currently still unknown.

FIG. 2. Understanding the nature of the IMS by various TEM characterizations. (a) Reciprocal space features of the IMS obtained along [101] zone axis showing split reflections at 1/2{ooe} superlattice reflection positions and the splitting direction was along [111]. Note that only the split spots appear but the 1/2{ooe} superlattice

ACS Paragon Plus Environment

Crystal Growth & Design 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

reflections themselves disappear, suggesting missing of long-range ordering. (b) Dark-field image using the split reflections at the 1/2(101) superlattice reflection position showing periodic array of parallel nanosized stripes with sharp contrast. (c) Filtered lattice fringes with one set of superlattice reflections as shown in the FFT image inserted in Fig. 2d. APB is identified by noting lattice shift by half of the supperlattice vector (indicated by the solid blue lines). (d) Dark-field image using the (010) basic reflection showing the same periodic array of parallel nanosized stripes as those in (b) but with faint contrast.

3.2 Constructing the reciprocal lattice of the IMS The three dimensional (3D) reciprocal space features of the IMS have been investigated by systematic tilting experiments (Fig. 3). Six zone axes diffraction patterns of an identical area were obtained, which were marked by solid black dots in the stereographic projection point diagram (Fig. 3e). Four of six zone axes SAED patterns were shown in Fig. 3 and DF images using the superlattice reflection at a 1/2{ooe} position were presented below the corresponding SAED patterns. The [001] diffraction pattern is indexed arbitrarily out of the three equivalent directions and the rest of zone axis patterns are indexed self-consistent with the [001] zone axis. It can be seen that the 1/2{ooe} reciprocal lattice points locating on [001] and [112] zero-order Laue zone (ZOLZ) do not split (Fig. 3a and 3c) while those on [101] ZOLZ all split along the [111] direction (Fig. 3c). On [113] SAED pattern (Fig. 3b), some of the superlattice reflections split while others do not. On the [113] SAED pattern (Fig. S2), none of the superlattice reflections split. The 1/2(121) superlattice reflection shows splitting on [101] SAED patterns while its splitting turns to be invisible upon tilting the specimen to the [113] zone axis. This is due to that the viewing direction becomes close to the splitting direction, making splitting undistinguishable. DF images acquired using superlattice reflections without splitting again only show submicron domains separated by APBIS (see Fig. 3a1 and Fig. 3a2). DF images using split superlattice reflections, as expected, show additional sharp parallel nanodomains in the submicron antiphase domains (see Fig. 3b2 and Fig. 3d1). Based on the trace analysis using Fig. 3b2 and Fig. 3d1, the nanodomain boundary was determined to locate on the (111) plane which is consistent to the HREM image in Fig. 2c. Therefore the angle between each viewing direction and the nanodomain boundary can be calculated and is shown in Fig. 3e. According to the above observations, the visibility of parallel nanodomains is determined by both the reflections used for DF imaging and viewing direction. On the one hand, APB as a kind of planar defects were formed by a lattice displacement R which is determined to be R=[001] in the present study according to the systematic tilting experiments and crystallographic considerations (see supporting information for details). The invisibility criterion for APB should be g ⋅ R = n where g is the reflection used for DF imaging and n is an integer. On the other hand, parallel domains could only be seen when the domain boundary is nearly parallel to the viewing direction, otherwise they would overlap and could hardly be discriminated. Thus, the present investigation indicates that the parallel nanodomains are two-dimensional, i.e. thin platelets on the {111} plane.

ACS Paragon Plus Environment

Page 6 of 15

Page 7 of 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Crystal Growth & Design

FIG. 3. Investigation of 3D reciprocal space features of the IMS by systematic tilting. (a), (b), (c) and (d) are SAED patterns of the IMS obtained along [001], [113], [112] and [101] zone axis respectively. (a1), (a2), (b1), (b2), (c1), (d1) are dark-field images using the superlattice reflection labelled with 1 and 2 in (a), (b), (c) and (d) respectively. (e) is part of [001] stereographic projection of pseudocubic perovskite showing 6 poles (marked by solid black dots) that have been successively obtained by tilting. The degree beside the 6 poles showed the angle between viewing direction and (111) plane which is the indices of APB based on the trace analysis using (b2) and (d1). Here only 4 of 6 poles were presented and corresponding convergent beam electron diffraction patterns were inserted in these SAED patterns.

Systematic tilting investigations provide much useful informations for constructing the reciprocal lattice of IMS. However, it is a pity that our TEM cannot tilt the specimen by a very large angle. Thus, the [111] zone axis could not be obtained by in-situ tilting from [001], which required 54° of tilting. The [111] zone axis contains the 1/2{ooe} superlattice reflections most close to the reciprocal lattice origin and is essential to construct the reciprocal lattice of IMS. In this case, the [111] SAED pattern has been investigated separately in another area. The [111]-oriented DF image (Fig. 4) shows the same domain configurations as those in Fig. 1-3. In the [111] SAED pattern, three type of 1/2{ooe} superlattice reflections appear while two of them split and the rest one does not.

ACS Paragon Plus Environment

Crystal Growth & Design 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

FIG. 4. [111] SAED pattern showing 3 different types of the 1/2{ooe} superlattice reflections most close to reciprocal lattice origin and corresponding DF images confirm this area for the [111] SAED has the same morphology feature as Fig. 1~3.

According to the invisibility criterion of g ⋅ R = n (here, R=[001]), we have constructed the reciprocal lattice of IMS with the modulation plane on (111) as shown in Fig. 5. The 1/2(ooe) superlattice reflections (located on the (001) reciprocal planes) do not split (g ⋅ R = n) while both 1/2(eoo) and 1/2(oeo) superlattice reflections (located on (100) and (010) reciprocal planes, respectively) will split (g ⋅ R ≠ n). The constructed reciprocal lattice is well consistent to the observed diffraction patterns. The pair of satellite spots at the 1/2(101) superlattice reflection site just locate on the [101] ZOLZ and thus [101] SAED patterns present reflection splitting along [111] direction (Fig. 2a, 3d and 5b). The [111] ZOLZ simultaneously cuts non-split 1/2(110) superlattice reflection and split reflections of 1/2(011) and 1/2(101) (Fig. 5c) thus show the corresponding diffraction pattern as observed in Fig. 4. There are no split superlattice reflections on either [001] or [112] ZOLZ hence all 1/2{ooe} superlattice reflections on the [001] and [112] diffraction patterns do not show splitting (Fig. 3a and 3c).

ACS Paragon Plus Environment

Page 8 of 15

Page 9 of 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Crystal Growth & Design

FIG. 5. The construction of reciprocal lattice of IMS. (a) Reciprocal lattice of IMS with modulation plane on (111). The green arrows indicate split directions parallel to [111]. (b) and (c) are part of [101] and [111] ZOLZ, respectively.

It seems that for a definite displacement vector, e.g. R=[001], IMS presents a specific nanodomain configuration with parallel domain boundaries approximately locating only on one of {111}, i.e. (111). By considering comparatively high symmetry of the present pseudo-cubic structure of PZT97/3, lattice displacement may undergo along any of the three directions. This may evoke a complex picture showing parallel domains lying on different {111} planes, which actually has been observed in the present study. Figure 6 shows three kinds of incommensurate domains with boundaries locating on (111), (111) and (111), respectively. It can be seen that reflections on each of

ACS Paragon Plus Environment

Crystal Growth & Design 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1/2{ooe} superlattice reciprocal site (see inset of Fig. 6 at the upper right corner) consist of two pairs of satellite spots pointing at two of directions, respectively along with a dot reflection at the center. The two pairs of satellites refer to two kinds of parallel nanodomains on different {111} planes, either of which was generated via a different R= displacement vector. The non-split dot reflection at the center indicates the third kind of parallel nanodomains that are invisible due to g ⋅ R = n for the third R= vector but can be seen if other g is applied in DF imaging (see DF images in Fig. 6).

FIG. 6. A [111] SAED pattern showing reciprocal space features of three incommensurate domains with different  ), (111) and (111), respectively. Inset at upper right corner is the orientations, whose boundaries located at (111 magnified image of reflections at a 1/2{101 superlattice site, which consist of two pairs of satellites referring to two oriented parallel nanodomains, respectively and a non-split reflection at the center referring to invisibility of the third sets of nanodomains. Alternate appearing of nanodomains on the DF images using different 1/2{101 reflections suggests the presence of all of the three R= displacement vectors in this area.

3.3 Growth process of the IMS Periodic array of parallel nanodomains are the typical features of IMS in PZT97/3. Nucleation and growth of parallel domains are of great interest in the present study. We happened to observe different growth stages of parallel domains in one picture as seen in Fig. 7. In Fig. 7a, the very small circles marked by yellow arrows are periodic domain boundaries which just nucleate. At the right sides of the DF image, the nuclei have grown to a larger size and arranged periodically. At other places of the DF image, the intermediate growth stage of IMS can also be observed with a feature of

ACS Paragon Plus Environment

Page 10 of 15

Page 11 of 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Crystal Growth & Design

just several parallel stripes. In Fig. 7b, the schematic of the growth process of the IMS was proposed. At first, several nucleation of domain boundaries will form at different places. Then, more and more domain boundaries will form and they arrange at a nearly equal interval. At last, the whole grain is full of the periodic array of parallel domain boundaries and the normal structure transforms to the incommensurate one and the curved APB was formed at the intersection of two incommensurate domains with same orientation (Fig. 1 and 3 ).

FIG. 7. Investigation of growth process of the IMS. (a) DF images showing different growth stages of IMS. The very small circles marked by yellow arrows are periodic domain boundaries which just nucleated. (b) Schematic of the growth process of the IMS.

It’s has been known for a long time that the IMS acts as a bridge phase between paraelectric phase at high temperature and FE/AFE phase at low temperature in Zr-rich PZT. In IMS, the atom position and spontaneous polarization were modulated in a particular way and its structural character will be inherited to some extent in the FE/AFE phase which has a critical role in understanding the origin of its high-performance stored-energy properties and phase transformation between FE and AFE. Yet, much of what we knew about the IMS in Zr-rich PZT was based on macroscopic measurements such as hysteresis loop and dielectric spectroscopy. The information presented here will provide additional insight in the IMS and lay the basis for further study including: What are the crystal structure and polarization configuration of the IMS? Is the IMS ferroelectricity or antiferroelectricity? How the IMS transform to FE/AFE?

4. CONCLUSION In this study, we have focused on the structural features of IMS in Zr-rich PZT including

ACS Paragon Plus Environment

Crystal Growth & Design 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

morphologies in real space, crystallographic information in reciprocal space, the growth process and nature of the IMS. Morphologies of the IMS. The IMS appears as a two-dimensional periodic nanodomains which locate on {111} planes and have a displacement vector R = across the nanodomain boundaries. That is, the IMSs have a long period ordering along a direction with a periodicity of about 30 {111} spacings. Periodic nanodomains have been found to assemble into the submicron domain which is enclosed by APBIS and can only be observable when the nanodomain boundaries deviates from the viewing directions by a small angle. Reciprocal configuration of the IMS. The IMS is characterized in reciprocal space by a set of strong basic reflections of pseudo-cubic unit cell together with a set of 1/2{ooe} superlattice reflections with or without splitting. For a certain R= displacement vector for the formation of nanodomain boundaries, 1/2{ooe} superlattice reflections on two of the three equvilent {100} reciprocal planes will split along one of the equvilent directions while the others do not split (Fig. 5a). IMS nanodomains could be formed simultaneously via all of the three equivalent displacement vectors giving a complex map of reciprocal space which is simply the superimposition of individuals (Fig. 6). Nature of the IMS. The DF images using either basic reflections or superlattice reflections yet showed the same periodic array of parallel nanodomain structures of the IMS indicating that IMS domains are not only antiphase domains but also electric domains. Growth process of the IMS. At first, nanodomains may nucleate randomly at different places. Then, more and more domain boundaries will form and they arrange in parallel with a nearly equal interval. Further growth involves extending of domain boundaries in length direction and merging of neighboring domain boundaries. Eventually the IMS periodic parallel nanodomains cover the whole grain.

ACKNOWLEDGMENTS This work is supported by National Key R&D Program of China (2016YFA0201103), Science and Technology Commission of Shanghai Municipality (16DZ2260603), Shanghai Technical Platform for Testing and Characterization on Inorganic Materials (14DZ2292900), International Partnership Program of Chinese Academy of Sciences (GJHZ1821), National Natural Science Foundation of China (11774366).

REFERENCES (1) Kittel, C. Theory of Antiferroelectric Crystals. Phys. Rev. 1951, 82, 729-732. (2) Cohen, R. E. Origin of Ferroelectricity in Perovskite Oxides. Nature 1992, 358, 136-138. (3) Kalinin, S. V. Multiferroics: Making a Point of Control. Nat. Phys. 2017, 13, 115-116. (4) Bai Yang. Zeng Tao, Shen Xi-Xun, Wang Bao-Feng, Dong Xian-Lin, Zhou Zhi-Yong. Investigation on the Mechanical and Ferroelectric Properties of the Porous PZT 95/5 Ceramics. J. INORG. MATER. 2014, 29, 758-762. (5) Rödel, J.; Webber, K. G.; Dittmer, R.; Jo, W.; Kimura, M.; Damjanovic, D. Transferring Lead-Free Piezoelectric Ceramics into Application. J. Eur. Ceram. Soc. 2015, 35, 1659-1681. (6) Hao, X.; Zhai, J.; Kong, L. B.; Xu, Z. A Comprehensive Review on the Progress of Lead Zirconate-Based Antiferroelectric Materials. Prog. Mater Sci. 2014, 63, 1-57.

ACS Paragon Plus Environment

Page 12 of 15

Page 13 of 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Crystal Growth & Design

(7) Woodward, D.; Knudsen, J.; Reaney, I. Review of Crystal and Domain Structures in the PbZrxTi1−xO3 Solid Solution. Phys. Rev. B 2005, 72. (8) Sawaguchi, E.; Maniwa, H.; Hoshino, S. Antiferroelectric Structure of Lead Zirconate. Phys. Rev. 1951, 83, 1078-1078. (9) Corker, D. L.; Glazer, A. M.; Dec, J.; Roleder, K.; Whatmore, R. W. Re-Investigation of the Crystal Structure of the Perovskite Pbzro3 by X-Ray and Neutron Diffraction. Acta Crystallogr B 1997, 53, 135-142. (10) Glazer, A. M.; Baba-Kishi, K. Z.; Pang, G. K. H.; Tai, C. W. Influence of Short-Range and Long-Range Order on the Evolution of the Morphotropic Phase Boundary in Pb(Zr1−xTix)O3. Phys. Rev. B 2004, 70. (11) Baba-Kishi, K. Z.; Welberry, T. R.; Withers, R. L. An Electron Diffraction and Monte Carlo Simulation Study of Diffuse Scattering in Pb(Zr,Ti)O3. J. Appl. Crystallogr. 2008, 41, 930-938. (12) Yokota, H.; Zhang, N.; Taylor, A.; Thomas, P.; Glazer, A. M. Crystal Structure of the Rhombohedral Phase of PbZr1-xTixO3 Ceramics at Room Temperature. Phys. Rev. B 2009, 80. (13) Phelan, D.; Long, X.; Xie, Y.; Ye, Z. G.; Glazer, A. M.; Yokota, H.; Thomas, P. A.; Gehring, P. M. Single Crystal Study of Competing Rhombohedral and Monoclinic Order in Lead Zirconate Titanate. Phys. Rev. Lett. 2010, 105. (14) Zhang, N.; Yokota, H.; Glazer, A. M.; Thomas, P. A. Neutron Powder Diffraction Refinement of PbZr1-xTixO3. Acta Crystallogr B 2011, 67, 386-98. (15) Zhang, N.; Yokota, H.; Glazer, A. M.; Ren, Z.; Keen, D. A.; Keeble, D. S.; Thomas, P. A.; Ye, Z. G. The Missing Boundary in the Phase Diagram of PbZr1-xTixO3. Nat. Commun. 2014, 5, 5231. (16) Zhang, N.; Paściak, M.; Glazer, A. M.; Hlinka, J.; Gutmann, M.; Sparkes, H. A.; Welberry, T. R.; Majchrowski, A.; Roleder, K.; Xie, Y.; Ye, Z.-G. A Neutron Diffuse Scattering Study of PbZrO3 and Zr-Rich PbZr1-xTixO3. J. Appl. Crystallogr. 2015, 48, 1637-1644. (17) Balashova, E. V.; Tagantsev, A. K. Polarization Response of Crystals with Structural and Ferroelectric Instabilities. Phys. Rev. B 1993, 48, 9979-9986. (18) Viehland, D.; Dai, X. H.; Li, J. F.; Xu, Z. Effects of Quenched Disorder on La-Modified Lead Zirconate Titanate: Long- and Short-Range Ordered Structurally Incommensurate Phases and Glassy Polar Clusters. J. Appl. Phys. 1998, 84, 458. (19) Asada, T.; Koyama, Y. La-Induced Conversion between the Ferroelectric and Antiferroelectric Incommensurate Phases in Pb1−xLax(Zr1−yTi y)O3. Phys. Rev. B 2004, 69. (20) Viehland, D. Transmission Electron Microscopy Study of High-Zr-Content Lead Zirconate Titanate. Phys. Rev. B 1995, 52, 778-791. (21) Xu, Z.; Dai, X.; Li, J. F.; Viehland, D. Evidence of M-Type Oxygen Octahedral Rotations in the High-Temperature Rhombohedral Ferroelectric Phase Region of Pb(Zr0.95Ti0.05)O3. Appl. Phys. Lett. 1995, 66, 2963. (22) Ricote, J.; Corker, D. L.; Whatmore, R. W.; Impey, S. A.; Glazer, A. M.; Dec, J.; Roleder, K. A TEM and Neutron Diffraction Study of the Local Structure in the Rhombohedral Phase of Lead Zirconate Titanate. J. Phys.: Condens. Matter 1998, 10, 1767-1786. (23) Watanabe, S.; Koyama, Y. Roles of Ferroelectricity, Antiferroelectricity and Rotational Displacement in the Ferroelectric Incommensurate Phase of Pb(Zr1−xTix)O3. Phys. Rev. B 2001, 63.

(24) Watanabe, S.; Koyama, Y. Features of the Incommensurate Phase in Pb(Zr1−xTix)O3. Phys. Rev. B 2002, 66.

ACS Paragon Plus Environment

Crystal Growth & Design 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

For Table of Contents Use only Incommensurately modulated structures in Zr-rich PZT: periodic nanodomains, reciprocal configuration and nucleation Zhengqian Fu a,c,d 1, Xuefeng Chen Wang b * and Xianlin Dong b,d, *

b1

, Ping Lu a, c, Chenxi Zhu a, c Henchang Nie b, Fangfang Xu, a,c,d, *, Genshui

a

State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China. b The Key Lab of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China. c Analysis and Testing Center for Inorganic Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China. d School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China. TOC Graphic:

TOC Synopsis: The features of incommensurately modulated structures in Zr-rich PZT including periodic nanodomains, reciprocal configuration and growth process were investigated in details by TEM.

ACS Paragon Plus Environment

Page 14 of 15

Page 15 of 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Crystal Growth & Design

The supporting information is available: Listings of an example for large area with IMS, an example for the visibility of split superlattice reflections, the process for determining displacement vector and SAED patterns of a same grain before and after heat treatment.

ACS Paragon Plus Environment