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系統識別號 U0026-2108201814392100
論文名稱(中文) 高壓合成LixFe1-xOHFeSe以及不同製程參數下樣品的特性研究
論文名稱(英文) High pressure synthesis of LixFe1-xOHFeSe and the variation of its properties under different processing parameters
校院名稱 成功大學
系所名稱(中) 材料科學及工程學系
系所名稱(英) Department of Materials Science and Engineering
學年度 106
學期 2
出版年 107
研究生(中文) 鄭安宏
研究生(英文) An-Hung Cheng
學號 N56054156
學位類別 碩士
語文別 英文
論文頁數 98頁
口試委員 指導教授-齊孝定
共同指導教授-龔慧貞
口試委員-李旺龍
口試委員-許文東
中文關鍵字 β-FeSe  (LixFe1-x)OHFeSe  超導體  高壓合成 
英文關鍵字 β-FeSe  (LixFe1-x)OHFeSe  superconductor  high pressure synthesis 
學科別分類
中文摘要 本研究使用氫氧化鋰(LiOH)、針鐵礦粉末(α-FeO(OH))、以及由鐵粉與硒粉預先合成之β相硒化鐵(β-FeSe)作為起始物,藉由高壓粉末固態加熱製程,合成(LixFe1-x)OHFeSe超導體,並透過調節主要製程參數包括起始物比例、外加壓力、溫度、反應時間,試圖找到合成(LixFe1-x)OHFeSe純相樣品之條件。實驗已嘗試壓力範圍0.5~1.25 GPa,溫度範圍300~500℃,反應時間24~48小時。實驗結果發現所有合成的樣品中都有生成(LixFe1-x)OHFeSe相,若要生成此相含量比例最高的樣品,須在下列條件下合成:起始物比例β-FeSe: LiOH: α-FeO(OH)=:1:1.1:0.1、外加壓力0.75~1 GPa、加熱溫度300~400℃。雖然樣品內仍存有二次相,但是作為起始物的β-FeSe幾乎未出現,表示反應完全。另外,量測樣品的磁性時,都有在12~14 K出現明顯的峰值,起因於(LixFe1-x)OHFeSe引起的自旋玻璃態,可做為成功合成此相的憑證之一。可惜的是,磁性及電性量測都未觀察到超導性。最後,本研究也探討了不同的製程參數對於(LixFe1-x)OHFeSe晶格常數及其物理性質的影響。
英文摘要 Suitable synthesis conditions, including the starting chemicals and compositions, applied pressures, reacting temperatures, and times, for the synthesis of a pure phase of (LixFe1-x)OHFeSe were studied. The starting chemicals included pre-synthesized β-FeSe from Se and Fe, LiOH·H2O, and α-FeO(OH) powders. The following ranges of synthesis parameters were attempted: pressure 0.5~1.25 GPa, temperatures from 300~500 ℃, and a reaction time of 24~48 hours. The results indicated that (LixFe1-x)OHFeSe appeared in all samples, but the optimal composition, which contained the highest amount of the desired (LixFe1-x)OHFeSe was β-FeSe:α-FeO(OH):LiOH=1:0.1:1.1. The proper ranges of sintering temperature and external pressure were 300~400℃ and 0.75~1 GPa, respectively. Although it was found that some secondary phases, i.e. δ-FeSe, (Li0.63Fe0.37)FeO2, etc. β-FeSe, one of the starting chemicals, which had usually appeared before, were successfully eliminated from the samples, indicating that it was reacted completely. An anomaly was observed in all of the samples at about 12 K~14 K in the magnetic susceptibility measurements, which was considered to be glassy magnetic behavior. However, no obvious superconductivity was found in either the magnetic and electrical measurements. Based on the x-ray diffraction data, the lattice constants of the synthesized (LixFe1-x)OHFeSe were refined using Total Pattern Analysis Solution (TOPAS) software, allowing the influences of the processing parameters on the lattice constants to be discovered.
論文目次 摘要 I
Abstract II
致謝 III
Contents IV
Contents of tables VII
Contents of figures VIII
Part 1. Introduction 1
Part 2. Basic theory and paper review 3
2-1. History of superconductors 3
2-1-1. Discovery of superconductors 3
2-1-2. Development of superconductors 3
2-1-3. Applications and future of superconductors 5
2-2. Characteristics of superconductors 6
2-2-1. Basic properties of superconductors [18] 6
2-2-2. Critical parameters of superconductors [18] 7
2-2-3. Types of superconductors [18] 8
2-3. Theories of superconductors 10
2-3-1. Relation between thermodynamics and superconductivity [20] 10
2-3-2. Two-fluid model [21] 11
2-3-3. London equations [22] 11
2-3-4. BCS theory [23] 13
2-3-5. Possible mechanism for unconventional superconductors 13
2-4. High-temperature superconductors 15
2-4-1. Cuprate superconductors 15
2-4-2. Iron-based superconductors 16
2-4-3. Comparison between cuprate superconductors and iron-based superconductors 17
2-5. Iron-based superconductor: FeSe 19
2-5-1. Generality of magnetic materials 20
2-5-2. Introductions of β-FeSe and its related compounds 22
2-5-3. Recent researches about β-FeSe 23
2-5-4. Recent researches about (LixFe1-x)OHFeSe 27
Part 3. Synthesis and facilities 30
3-1. Experimental facilities 30
3-1-1. Commonly-used facilities 30
3-1-2. Large volume high pressure apparatus (LVHPA) [71, 72] 30
3-2. Materials and chemicals 33
3-2-1. Commonly-used chemicals 33
3-2-2. Materials used in LVHPA 33
3-3. Experimental procedures 35
3-3-1. Solid-state reaction under normal pressure 36
3-3-2. Solid-state reaction under high pressure 37
3-4. Analyzing facilities 39
3-4-1. Phase determination (XRD) 39
3-4-2. Surface topography (SEM) and composition analysis (EDS) 41
3-4-3. Detection of superconductivity (SQUID) 41
3-4-4. Measurement of electrical properties (PPMS) 42
Part 4. Results and discussions 43
4-1. Reaction of β-FeSe, LiOH, and α-FeO(OH) under high pressure 46
4-1-1. Synthesis of β-FeSe 46
4-1-2. Results of changing precursor 49
4-1-3. Influences of composition on forming phases 51
4-1-4. Influences of external pressure on forming phases 58
4-1-5. Influences of sintering temperature on forming phases 61
4-1-6. Influences of extending sintering time on forming phases 64
4-1-7. Influences of extending sintering time on forming phases with different applied pressure-temperature conditions 66
4-1-8. Summary 73
4-2. Analysis of magnetic and electrical properties 76
4-2-1. Results of M-T measurement 76
4-2-2. Results of R-T measurement 77
4-2-3. Results of M-H measurement 78
4-2-4. Summary 79
4-3. Microstructure and structure refinements 81
4-3-1. Microstructure and the analysis of composition 81
4-3-2. Influences of different processing parameters on lattice constants of synthesized (LixFe1-x)OHFeSe. 82
Part 6. Conclusion 91
References 92
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