DGIST Scholar: Fundamental Understanding and Development of Highly Conductive and Durable Bi2O3-based Superionic Conductors for Energy Conversion Applications

Department of Energy Science and Engineering Theses Ph.D.

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Fundamental Understanding and Development of Highly Conductive and Durable Bi2O3-based Superionic Conductors for Energy Conversion Applications

Title: Fundamental Understanding and Development of Highly Conductive and Durable Bi2O3-based Superionic Conductors for Energy Conversion Applications

Alternative Title: 에너지 변환 소자를 위한 초이온전도성 고내구성 비스무스 산화물 이온전도체의 기본특성 이해 및 소재 설계

Author(s): Incheol Jeong

DGIST Authors: Incheol Jeong ; Jong-Won Lee ; Kang Taek Lee

Advisor: 이종원

Co-Advisor(s): Kang Taek Lee

Issued Date: 2022

Awarded Date: 2022/02

Type: Thesis

Subject: Solid electrolyte, Ionic conductor, δ-Bi2O3, Computational materials science, Density functional theory

Description: Solid electrolyte, Ionic conductor, δ-Bi2O3, Computational materials science, Density functional theory

Table Of Contents: Ⅰ. Introduction 1
1.1 Motivation 1
1.2 Objective 2
Ⅱ. Background 3
2.1 Solid oxide ionic conductors 3
2.1.1 Zirconium based oxides 5
2.1.2 Ceria based oxides 6
2.1.3 Lanthanum based oxides 7
2.1.4 Bismuth based oxides 8
2.1.4.1 Crystal structure of δ-Bi2O3 10
2.1.4.2 Stabilization of cubic fluorite phase 10
2.1.4.3 Degradation mechanisms of ionic conductivity 11
2.2 Density Functional Theory 11
Ⅲ. Rational Design of Disordered δ-Bi2O3 via First-principles Calculations 20
3.1 Introduction 20
3.2 Computational details 21
3.3 Results and discussion 22
3.3.1 Structural Modelling of \delta-Bi2O3 22
3.3.2 Oxygen distribution of the disordered structures 23
3.3.3 Band gap of the disordered structures 24
3.3.4 Relative total energies and crystallographic features of the disordered structures 24
3.3.5 Calculating ionic conductivity of computationally designed \delta-Bi2O3 via FPMD simulation 25
3.4 Conclusion 26
Ⅳ. Elucidating the Role of Grain Boundary on Cubic-to-rhombohedral Phase Transition 38
4.1 Introduction 38
4.2 Computational details 40
4.3 Results and discussion 41
4.3.1 Local geometry change of Bi toward grain boundary 41
4.3.2 Modeling and validation of bulk-based cubic and rhombohedral phases 42
4.3.3 Bonding Characteristics 43
4.3.4 Electronic structure 44
4.3.5 Phase transition energetics 45
4.4 Conclusion 45
Ⅴ. Predicting the Effect of Transition Metals on Order-disorder Transition of Anion Sublattice 57
5.1 Introduction 57
5.2 Computational details 58
5.3 Results and discussion 59
5.4 Conclusion 61
Ⅵ. Summary 66
Ⅶ. References 69
Summary (In Korean) 80