Ce이 충진된 p형 Skutterudite계 소재의 조성 제어를 통한 열전성능 향상 연구 = Enhancement of thermoelectric properties through compositional optimization in Ce-filled p-type Skutterudites

다국어 초록 (Multilingual Abstract)

Thermoelectric（TE） generation is a promising technology for decentralized waste heat recovery. CoSb3-based filled skutterudites, adhering to the phonon-glass electron-crystal （PGEC） concept, are prominent TE materials. While n-type skutterudites have been widely studied, high-performance p-type counterparts are essential for practical module fabrication. Substituting Fe at the Co sites induces p-type conduction and enhances the Seebeck coefficient through strong Sb 5p–Fe 3d orbital hybridization. Among various fillers, Ce offers a superior Cost-to-ZT ratio for commercialization. However, optimizing TE performance requires a systematic composition design to simultaneously satisfy charge neutrality and phase stability.
In this study, a three-step sequential optimization strategy was employed to maximize the TE performance of Ce-filled p-type skutterudites. First, the Ce filling fraction was optimized in CexFe3.5Co0.5Sb12 to compensate for excessive holes generated by Fe substitution, confirming x = 1.0 as the critical solubility limit. Second, to suppress secondary phases caused by Sb volatilization during high-temperature synthesis, the Sb stoichiometry was tuned in Ce1.0Fe3.5Co0.5Sb12+y. The optimal ratio of Sb12.4 （y = 0.4） was experimentally determined to ensure structural stability and carrier mobility.
Finally, based on the optimized phase-stable matrix （Ce1.0Fe4-zCozSb12.4）, the Fe/Co substitution ratio （z = 0.25, 0.5, 0.75, 1, 1.25） was adjusted to precisely control the hole concentration. The optimized z = 0.5 composition（Ce1.0Fe3.5Co0.5Sb12.4） exhibited maximized band degeneracy and optimal carrier concentration, yielding an outstanding power factor of 32.7 x 10-4 W/mK2. Concurrently, the synergistic effects of point defect scattering and Ce rattling minimized the lattice thermal conductivity to 0.8 W/mK. Consequently, a significantly enhanced maximum ZT value of 1.07 was achieved. This study demonstrates that the sequential control of filler concentration, phase stability, and charge compensation is a highly effective approach for developing high-efficiency p-type filled skutterudite TE materials.

목차 (Table of Contents)

• 제 1장 서론 1
• 제 2장 이론적 배경 5
• 2.1. 열전현상 5
• 2.1.1. 제벡효과(Seebeck effect) 5
• 2.1.2. 펠티에효과(Peltier effect) 6
• 2.1.3. 톰슨효과(Thomson effect) 7
• 2.2. 열전특성 9
• 2.2.1. 전기전도도(Electrical conductivity) 9
• 2.2.2. 제벡계수(Seebeck coefficient) 10
• 2.2.3. 열전도도(Thermal conductivity) 12
• 2.2.4. 무차원성능지수(Figure of merit) 14
• 2.3. Skutterudite 열전소재 16
• 2.3.1. Skutterudite의 특성 16
• 2.3.2. Ce 충진 p형 Skutterudite 연구동향 24
• 제 3장 실험방법 29
• 3.1. Ce이 충진된 p형 Skutterudite 분말 제조 29
• 3.2. Ce이 충진된 p형 Skutterudite 소결체 제조 30
• 3.3. 분석 및 측정 34
• 3.3.1. 미세구조 분석 34
• 3.3.1.1. X-ray Diffraction(XRD) 34
• 3.3.1.2. Scanning Electron Microscope(SEM) 34
• 3.3.1.3. Transmission Electron Microscope(TEM) 35
• 3.3.1.4. Electron Probe Micro Analyzer(EPMA) 35
• 3.3.2. 열전특성 측정 36
• 3.3.2.1. 전기전도도, Seebeck 계수, 출력인자 36
• 3.3.2.2. 캐리어 농도, 캐리어 이동도 36
• 3.3.2.3. 열전도도 38
• 제 4장 실험 결과 및 고찰 42
• 4.1. CexFe3.5Co0.5Sb12의 열전 특성 42
• 4.1.1. CexFe3.5Co0.5Sb12의 미세구조 특성 42
• 4.1.2. CexFe3.5Co0.5Sb12의 전기적 특성 48
• 4.1.3. CexFe3.5Co0.5Sb12의 열적 특성 53
• 4.1.4. CexFe3.5Co0.5Sb12의 열전 성능 57
• 4.2. Ce1.0Fe3.5Co0.5Sb12+y의 열전 특성 60
• 4.2.1. Ce1.0Fe3.5Co0.5Sb12+y의 미세구조 특성 60
• 4.2.2. Ce1.0Fe3.5Co0.5Sb12+y의 전기적 특성 65
• 4.2.3. Ce1.0Fe3.5Co0.5Sb12+y의 열적 특성 70
• 4.2.4. Ce1.0Fe3.5Co0.5Sb12+y의 열전 성능 74
• 4.3. Ce1.0Fe4-zCozSb12.4 열전 특성 77
• 4.3.1. Ce1.0Fe4-zCozSb12.4의 미세구조 특성 77
• 4.3.2. Ce1.0Fe4-zCozSb12.4의 전기적 특성 81
• 4.3.3. Ce1.0Fe4-zCozSb12.4의 열적 특성 86
• 4.3.4. Ce1.0Fe4-zCozSb12.4의 열전 성능 90
• 제 5장 결론 93
• 제 6장 참고문헌 97