Doctoral Dissertations

Keywords and Phrases

ab initio; CALPHAD; Landau-Devonshire theory; Ternary database; Thermodynamic model; Wurtzite ferroelectric

Abstract

This dissertation advances the CALPHAD (CALculation of PHase Diagrams) approach for thermodynamic modeling which often lacks sufficient description of crystal lattices for critical phases in multicomponent system. Additionally, CALPHAD does not consider the structural features and its connection with functional properties for functional materials. To address these issues, a novel dual-ordered sublattice model for the κ-phase in Fe-Al-C system, (Fe,Al)3(Fe,Al)1(C,Va)1(C,Va)3, is introduced that improves predictions of equilibrium compositions and phase stability by accounting for both substitutional and interstitial ordering. For the Fe-B-C system, new sublattice formulations for FCC [(Fe)1(C,B,Va)1] and BCC [(Fe,B)1(C,B,Va)3], phases enhance boron solubility predictions and reveal insights into metatectic reactions and boride formation. To model field-responsive properties, a Landau-based thermodynamic energy function is developed for the wurtzite MgxZn1-xO system. Using DFT-derived structural and piezoelectric data, the model predicts ferroelectric, dielectric, and piezoelectric behaviors in thin films. CALPHAD is concurrently used to assess phase stability and solubility limits. Together, these advancements form a unified framework that expands CALPHAD’s accuracy and functionality. By combining thermodynamic modeling of structural alloys with property prediction in functional materials, this work supports the ICME vision for integrated, predictive materials design.

Advisor(s)

Gu, Yijia

Committee Member(s)

Emdadi, Arezoo
Wen, Haiming
Medvedeva, Julia E.
Bartlett, Laura

Department(s)

Materials Science and Engineering

Degree Name

Ph. D. in Materials Science and Engineering

Publisher

Missouri University of Science and Technology

Publication Date

Summer 2025

Journal article titles appearing in thesis/dissertation

Paper I, found on pages 20–53, has been published to CALPHAD (2024), https://doi.org/10.1016/j.calphad.2024.102749.

Paper II, found on pages 54-75, are intended manuscript for CALPHAD journal.

Paper III, found on pages 76–102, is intended for submission to npj Computational Materials.

Pagination

xiv, 112 pages

Note about bibliography

Includes_bibliographical_references_(pages 108-111)

Rights

© 2025 Kyaw Hla Saing Chak , All Rights Reserved

Document Type

Dissertation - Open Access

File Type

text

Language

English

Thesis Number

T 12533

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