Zhang, Junyan
(2020)
Ferroelectric Properties of Aurivillius Phase Bi5CrxFe1-xTi3O15 Films.
Master's Thesis, University of Pittsburgh.
(Unpublished)
Abstract
Aurivillius phase Bi5CrxFe1-xTi3O15 (BCxF1-xTO) thin films are prepared by the chemical solution deposition method and the effect of Cr content on the structural, optical bandgap, electric transport, and dielectric/ferroelectric properties of BCxF1-xTO thin films are investigated in detail. X-ray diffraction analysis shows that all of BCxF1-xTO films are a complete solid solution and maintain Aurivillius structure. The replacement of Fe3+ with smaller Cr3+ decreases the overall lattice volume and gradually increases the bandgap of BCxF1-xTO thin film. The random mixing of Cr and Fe in BCxF1-xTO decreases the long-range lattice distortion in a-b plane and the smallest a/b ratio is found at BC0.5F0.5TO. Cr-doping also changes the gran shape from the spheres to plates and BC0.5F0.5TO consists of only plate-like grains. This indicates that a decrease in the lattice distortion promotes the grain growth along a-b plane and facilitates the appearance of the inherent crystal shape of Aurivillius phase. Ferroelectric properties of BCxF1-xTO films are examined by measuring P-E hysteresis loops. Cr-doping increases saturated polarization (PS) and decreases coercive field (EC). When 50 atomic % of Cr is doped, PS and EC of BC0.5F0.5TO is 35 μC/cm2 and 125 kV/cm, respectively. This is due to the fact that the decrease in the long-range distortion in a- b plane promotes the alignment of ferroelectric dipoles under electric field. The frequency dependent dielectric properties at different temperatures and the leakage current show that Cr doping increases the carrier concentration and the space charge polarization. However, the plate- like shape grains of Cr-rich BCxF1-xTO films suppress the transport of carriers from grains to grains and prevents a dramatic increase in the leakage current. The results of this study provide a design rule to control the ferroelectric of Aurivillius phase BCxF1-xTO thin films by modifying the composition and lattice distortion.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
29 July 2020 |
| Date Type: |
Publication |
| Defense Date: |
25 March 2020 |
| Approval Date: |
29 July 2020 |
| Submission Date: |
31 March 2020 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
68 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Materials Science and Engineering |
| Degree: |
MSMSE - Master of Science in Materials Science and Engineering |
| Thesis Type: |
Master's Thesis |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
ferroelectricity, ferroelectric material |
| Date Deposited: |
29 Jul 2020 18:38 |
| Last Modified: |
29 Jul 2020 18:38 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/38517 |
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