NICOP - Contribution of polar nano-regions to the large piezoelectric response in Pb-based relaxor ferroelectrics
Abstract
The crystals of Pb-based relaxor-ferroelectric solid solutions (such as Pb(Mg1/3Nb2/3)O3-PbTiO3 andits derivatives) exhibit the hig"hest electro-mechanical properties among practically useful piezoelectricmaterials (d33>2000 pC/N, k33>90%). Relaxor-ferroelectrics" have been thus widely used in transducersfor medical imaging and for underwater sensor applications. The origin of the large response in thesesolid solutions has been usually attributed to the effects of the morphotropic phase boundary andfacilitated polarizat"ion rotation in that region of the phase diagram. Possible contributions of themesoscopic features (polar nano-regions, hierarchica""l domain structure) have also been invoked toexplain the large response, but little direct experimental evidence existed for their"" role in the largeproperties. In a recent experimental study, Li et al.1 showed that the large macroscopic electromechanicalrespon""se in these materials unexpectedly and abruptly freezes at temperatures below about150 K, indicating an important contribution from"" the dynamics of the mesoscopic objects. In thisproject, we propose to reveal mechanisms by which polar nano regions contribute to" the largepiezoelectric response in relaxor-ferroelectrics. We will accomplish this by a combined (i) study of thecontribution of the dynamics of polar regions to the macroscopic properties and (ii) in-situ atomic-levelhigh resolution Scanning TEM investigation of domains and polar regions. The dynamics of polarregions will be studied by measuring the amplitude and the phase of the polarization response as afunction of the driving field amplitude and frequency. This method is very sensitive and candiscriminate among displacement of domain walls in soft and hard ferroelectric materials and motion ofpolar regions in ergodic and nonergodic phases" of relaxors.2 In the high-resolution microscopicinvestigation, we will identify structure of polar nano regions on atomic level an"d observe its evolutionover a large temperature range. We plan to apply electric field in-situ and observe dynamics of polarnano regions with atomic resolution below and above the threshold temperature. We will also observeand semiquantitatively determine atomic-level strains associated with polar nano regions in interior ofdomains in relaxor-ferroelectric single crystals and ceramics. Those studies will be complemented by anin-situ investigation using Hard X-ray Microscopy.3 The technique allows observation of strains aroundferroelectric domain walls in the bulk of a crystal or in a ceramic grain embedded deep in the bulk. Thistechnique is particularly useful to avoid skin effects characteristic for relaxor-ferroelectric singlecrystals. The combined results of the macroscopic and microscopic measurements are expected toenable us to identify mechanisms of the large electro-mechanical response in relaxo"r-ferroelectrics.We have already carried out considerable preliminary work in other ferroelectrics with complexchemistry, which sh"ows that these ambitious goals can be successfully achieved within the proposedplan of work.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 26, 2018
- Source ID
- N629091812078
Entities
People
- Dragan Damjanović
Organizations
- Office of Naval Research
- Swiss Federal Institute of Technology in Lausanne
- United States Navy