Lead-Free Relaxor Ferroelectric Ceramics for High-Strain Actuator Applications

Mostovych, Nicholas

Full Metadata

Overview

Year:: 2018
Contributor:: Mostovych, Nicholas (creator); Kingon, Angus (Advisor); Kim, Seunghyun (Reader); Pradeep, Guduru (Reader); Brown University. Engineering: Materials Science Engineering (sponsor)
Genre:: theses
Subject:: Piezoelectrics; Piezoelectric devices; Piezoelectric materials; relaxor ferroelectrics; field-induced phase transition
Extent:: xi, 118 p.
DOI: https://doi.org/10.26300/0g5b-aq82

Files

Description

Abstract:: The ternary solid solution (1-x)Bi1/2(Na0.78K0.22)1/2TiO3 ̶ xBiMg1/2Ti1/2O3 (BNKT-BMT) was investigated for high-strain actuator applications. BNKT-BMT is a Bi1/2Na1/2TiO3 (BNT)-based relaxor ferroelectric which shows promise as a high-strain lead-free piezoceramic with tunable macroscopic properties. Three areas of scientific interest were investigated. The first area was how to maximize the macroscopic temperature-dependent strain performance of the BNKT-BMT system. The macroscopic properties of the BNKT-BMT system were characterized as a function of temperature and BMT composition. A gradual transition toward ergodic behavior was observed at elevated temperatures and higher BMT concentrations. The second area of study was to provide further evidence to the existing microscopic description of ergodicity in relaxor ferroelectrics. Piezoresponse Force Microscopy was performed using the Band Excitation technique to compare the microscopic domain behavior for low BMT-content compositions that exhibit macroscopic nonergodic behavior and high BMT-content compositions that exhibit ergodic behavior. The high BMT-content BNKT-4%BMT exhibited a dramatic shift toward a disrupted polar state in which nano-domains (10 – 100 nm in size) were observed in a labyrinth pattern. The final area of study in this work was the degradation and failure modes of the BNKT-BMT system as a function of thickness. Bulk ceramic BNKT-BMT material was thinned down to 50 μm – 10 μm and then subjected to ramped-voltage stress testing. The BNKT-BMT system exhibited a strong thickness dependence in dielectric breakdown strength down to 10 μm, which indicates that the primary breakdown mechanism is extrinsic in nature.
Notes:: Thesis (Ph. D.)--Brown University, 2018

Content

Access Conditions

Rights: In Copyright
Restrictions on Use: Collection is open for research.

Citation

Mostovych, Nicholas, "Lead-Free Relaxor Ferroelectric Ceramics for High-Strain Actuator Applications" (2018). Materials Science Engineering Theses and Dissertations. Brown Digital Repository. Brown University Library. https://doi.org/10.26300/0g5b-aq82

Relations

Collection:

Materials Science Engineering Theses and Dissertations

Theses and Dissertations for the Materials Science Engineering department.
...