Bustillo, KC

Ciston, J

Deng, Y

Ercius, Peter

Gammer, C

Minor, AM

Ophus, C

Song, Chengyu

Zhang, Ruopeng

English

eScholarship - University of California

Lawrence Berkeley National LaboratoryLBL PublicationsTitleAtomic Resolution Probing of Phase Transformations and Domain Evolution During Large Superelastic Deformation in Ferroelectrics with in situ TEMPermalinkhttps://escholarship.org/uc/item/3pm6c1gnJournalMicroscopy and Microanalysis, 25(S2)ISSN1431-9276AuthorsDeng, YGammer, CCiston, Jet al.Publication Date2019-08-01DOI10.1017/s143192761900998x Peer reviewedeScholarship.org Powered by the California Digital LibraryUniversity of CaliforniaAtomic Resolution Probing of Phase Transformations and Domain Evolution During Large Superelastic Deformation in Ferroelectrics with In Situ TEMY. Deng1*, C. Gammer2, J. Ciston3, Peter Ercius3, C. Ophus3, K. C. Bustillo3, Chengyu Song3, Ruopeng Zhang3,4 and A. M. Minor3,4 1. Physics School and Modern Analysis Center, Nanjing University, Nanjing, China, 2100932. Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, 8700 Leoben, Austria3. National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 947204. Department of Materials Science & Engineering, University of California, Berkeley, CA 94720* Corresponding author: dengyu@nju.edu.cn Intrinsically  brittle  Ferroelectrics  have attractive applications  such  asflexible/wearable  electronic  devices and  mechanically-written  high-densitymemory that depend on both functional and mechanical performance [1-3]. Onepotential  way  to  mitigate  their  brittle  behavior  is  through large superelasticdeformation  stemming  from  strain-driven  phase  transformations  and  domainevolution. Therefore,  we  investigated  free-standing  single-crystal  BaTiO3 andPb(Mg1/3Nb2/3)O3-PbTiO3 sub-micrometer  pillars  during large  superelasticdeformation,  directly  observing  the  stress-induced  phase  transformations  anddomain  evolution by  using  in  situ  Scanning  Transmission Electron  Microscope(STEM). We found ultra-small and multiple-phase coexistence with sizes down to afew unit cells,  and we were able to study them at atomic resolution  while  underload.  Notably,  extremely  small  phase  transformation structures  and  domainstructures are often introduced during the large superelastic deformations sincethe stress field is not screened in ferroelectrics, as compared to the situation withelectrical field or thermal cycling. We prepared the free-standing sub-micrometer pillars from bulk single crystalsof  BaTiO3 by Focused Ion Beam (FIB). The in situ observations  were carried outusing a  probe  and imaging Cs-corrected  (S)TEM from FEI  providing  sub-atomicresolution  (TEAM  I at  NCEM)  equipped  with  a  direct-electron-detector (K2-IS,Gatan). In situ mechanical testing was carried out using a picoindenter TEM holder(PI-95, Hysitron).  To limit the influence of the electron beam, we performed TEMobservations using a low current density (≤10-2A/cm2) and STEM measurementswere performed using a relatively low beam current (≤35pA). During deformationwe performed four-dimensional  scanning transmission electron microscope (4D-STEM) to provide phase and strain information from the unit-cell  to micrometerscale in order to map the deformed microstructure while the samples were underload [4-5].Through our in situ S/TEM experiments we were able to quantitatively studythe nucleation, forward growth, side growth and merging of the twinning domainsand bundle domains (as shown in Figure 1). At atomic resolution, we were able toobserve  the   nucleation  and  growth  of  the  strain-driven  phase  transformationstructures  during  the  large  superelastic  deformation. The  distributions  of  localstrains and mobile point defects were also analyzed. Based on  our  experimentalfindings, the ‘controversial’ large superelastic deformation in ‘brittle’ ferroelectricscan  be  well  understood with  a  model  that  accounts  for  multiple  mechanismscontributing at multiple length scales. In conclusion, the full superelastic deformation process and the  strain-drivenphase transformation and domain evolution during large superelastic deformationin ferroelectrics has been investigated at  multiple length scales by using in situS/TEM. Such  observations  provide  crucial  insight  into  the  multiple  mechanismsinvolved in superelastic deformation.        References[1] G. Catalan, J. Seidel, R. Ramesh and J. F. Scott, Rev. Modern Phys. 84 (2012) 119.[2] J. F. Scott, Science 315 (2007) 954.[3] Y. L. Tang, Y. L. Zhu, X. L. Ma, S. J. Pennycook, et. al. Science 348 (2015) 547.[4] C. Gammer, V. B. Ozdol, C.H. Liebscher, and A.M. Minor, Ultramicroscopy, 1 (2015) 155.[5] V.B. Ozdol, C. Gammer, X.G. Jin, P. Ercius, C. Ophus, J. Ciston and A.M. Minor,  Applied Physics Letters, 106 (2015) 253107.[6] The authors acknowledge support by the National Natural Science Foundation of China (Grants Nos. 50802039) and Natural Science Foundation of Jiangsu Province, China (Grant Nos. BK20151382), and the National Science Foundation through the STROBE Science and Technology Center. RZ acknowledges funding from the US Office of Naval Research under Grant No. N00014-12-1-0413 and N00014-17-1-2283. The electron microscopy work was performed at the Molecular Foundry, Lawrence Berkeley National Laboratory, which is supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Dept. of Energy under Contract # DE-AC02-05CH11231.  J.C. acknowledges additional support from the Department of Energy Early Career Research Program.Figure 1.  (a) The domain evolutions in a single-crystal BaTiO3 sub-micrometerpillar  under  compression loading.  We  use  the  models  below  to  illustrate  thedomain evolutions in the pillar. (b) HRSTEM observation on a domain wall. 

Atomic Resolution Probing of Phase Transformations and Domain Evolution During Large Superelastic Deformation in Ferroelectrics with in situ TEM

https://escholarship.org/uc/item/3pm6c1gn

Atomic Resolution Probing of Phase Transformations and Domain Evolution During Large Superelastic Deformation in Ferroelectrics with in situ TEM

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