Exploration of novel ferroelectric systems: determination of the underlying mechanisms

Author

• Sizhan Liu, New Jersey Institute of Technology

Document Type

Dissertation

Date of Award

8-31-2020

Degree Name

Doctor of Philosophy in Materials Science and Engineering - (Ph.D.)

Department

Committee for the Interdisciplinary Program in Materials Science and Engineering

First Advisor

Trevor Tyson

Second Advisor

Mark C. Croft

Third Advisor

Roger Lalancette

Fourth Advisor

Ken Keunhyuk Ahn

Fifth Advisor

Tao Zhou

Sixth Advisor

Cristiano L. Dias

Abstract

Modern environmental and sustainability issues, as well as the growing demand for applications in sensing and data storage, require the discovery and development of new functional materials. Ferroelectrics and multiferroics are materials that have played a central role in this arena. Because the central function of ferroelectrics is governed by spontaneous polarization response, understanding both the electronic and atomic response to external stimuli is important. In this work, a broad set of model systems were explored to determine the fundamental mechanisms involved in the formation of the ferroelectric phase.

Understanding atomic-level changes in structure is important for improving the properties of ferroelectric materials. The effect of external pressure, temperature, and particle size on the ferroelectric phase of in materials is studied in depth. Specific systems studied include Sn₂P₂S₆, Ca₃X₂O₇ layered oxides, LuFe₂O₄ and simple ABX3 perovskites. This thesis work involves measurements on multiple length scales- from the atomic length scale (atomic displacements) to the micron scale (polarization domain structures). The correlations between electric polarization and atomic and electronic structure (under varying pressure, temperature and magnetic fields) are studied using synchrotron X-ray diffraction (XRD), Raman spectroscopy, X-ray pair distribution function (PDF), X-ray absorption fine structure (XAFS), X-ray absorption near-edge structure (XANES) measurements and DFT modeling. The work combines research at NJIT, the National Synchrotron Light Source II (Brookhaven National Laboratory), the Advanced Photon Source (Argonne National Laboratory), and Oak Ridge National Laboratory.

Recommended Citation

Liu, Sizhan, "Exploration of novel ferroelectric systems: determination of the underlying mechanisms" (2020). Dissertations. 1906.
https://digitalcommons.njit.edu/dissertations/1906