Transmission electron microscopy investigation of the microstructural mechanisms for the piezoelectricity in lead-free perovskite ceramics

dc.contributor.advisor Xiaoli Tan
dc.contributor.author Ma, Cheng
dc.contributor.department Materials Science and Engineering
dc.date 2018-08-11T13:45:33.000
dc.date.accessioned 2020-06-30T02:44:11Z
dc.date.available 2020-06-30T02:44:11Z
dc.date.copyright Sun Jan 01 00:00:00 UTC 2012
dc.date.embargo 2013-06-05
dc.date.issued 2012-01-01
dc.description.abstract <p>Lead-free materials with superior piezoelectricity are in increasingly urgent demand in the current century, because the industrial standard Pb(Zr,Ti)O<sub>3</sub>-based piezoelectrics, which contain over 60 weight% of the toxic element lead, pose severe environmental hazards. Although significant research efforts have been devoted in the past decade, no effective lead-free substitute for Pb(Zr,Ti)O<sub>3</sub> has been identified yet. One of the primary hindrances to the development of lead-free piezoelectrics lies in the ignorance of the microstructural mechanism for the electric-field-induced strains in the currently existing compositions.</p> <p>In this dissertation, the microstructural origin for the high piezoelectricity in (1-<em>x</em>)(Bi<sub>1/2</sub>Na<sub>1/2</sub>)TiO<sub>3</sub>-<em>x</em>BaTiO<sub>3</sub> [(1-<em>x</em>)BNT-<em>x</em>BT], the most widely studied lead-free piezoelectric system, has been elucidated. The combination of dielectric characterization and conventional transmission electron microscopy (TEM) demonstrates that the phase relationship for unpoled ceramics is different from that for poled ceramics. This discovery leads to the update of the BNT-BT phase diagram that has been widely accepted for 20 years. The hot-stage TEM study further extends the updated phase diagram to 600 °C and clarifies the complicated relationship between the crystal/domain structures and dielectric properties. Based on these findings, the electric-field <em>in-situ</em> TEM investigation reveals that the morphotropic phase boundary (MPB) in this system, along with the associated piezoelectricity enhancement, could be created, destroyed, or even replaced by another MPB during electrical poling, an indispensable process for ferroelectric materials to exhibit usable piezoelectricity. The optimal piezoelectric response in the originally single-phase composition <em>x</em> = 7% is found to be the result of a stable MPB induced by electric fields during poling.</p> <p>The discovery summarized in this dissertation not only elucidates the microstructural mechanism for the high piezoelectricity in BNT-BT, but also fundamentally alters the long-standing guiding rule for designing superior piezoelectric materials. It suggests that even single-phase compositions, which were largely excluded before, may also exhibit strong piezoelectricity if stable MPBs form during poling. Such a paradigm shift adds a new dimension to the development of next generation high-performance piezoelectrics.</p>
dc.format.mimetype application/pdf
dc.identifier archive/lib.dr.iastate.edu/etd/12650/
dc.identifier.articleid 3657
dc.identifier.contextkey 4186401
dc.identifier.doi https://doi.org/10.31274/etd-180810-592
dc.identifier.s3bucket isulib-bepress-aws-west
dc.identifier.submissionpath etd/12650
dc.identifier.uri https://dr.lib.iastate.edu/handle/20.500.12876/26839
dc.language.iso en
dc.source.bitstream archive/lib.dr.iastate.edu/etd/12650/Ma_iastate_0097E_12895.pdf|||Fri Jan 14 19:26:47 UTC 2022
dc.subject.disciplines Chemistry
dc.subject.disciplines Condensed Matter Physics
dc.subject.disciplines Mechanics of Materials
dc.subject.keywords electric-field-induced phase transition
dc.subject.keywords ferroelectricity
dc.subject.keywords in-situ transmission electron microscopy
dc.subject.keywords morphotropic phase boundary
dc.subject.keywords piezoelectricity
dc.title Transmission electron microscopy investigation of the microstructural mechanisms for the piezoelectricity in lead-free perovskite ceramics
dc.type article
dc.type.genre dissertation
dspace.entity.type Publication
relation.isOrgUnitOfPublication bf9f7e3e-25bd-44d3-b49c-ed98372dee5e
thesis.degree.level dissertation
thesis.degree.name Doctor of Philosophy
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