本研究添加商用銀奈米線及銀奈米粉末至釔鋇銅氧超導塊材內，觀察添加物對晶體成長及超導性質的影響。為了探討添加物於超導性質中扮演的角色，本研究亦引用Due-Hughes釘扎機制數學模型建立一釘扎機制分析方法，並以部分超導體文獻及前人實驗結果做驗證，以本釘扎機制分析方法與文獻預期觀測到的釘扎機制是否相符，最後再將本分析方法分析運用於添加銀奈米線及奈米粉末之成果。
為了避免奈米線斷裂，本研究提出濕混及乾混等兩種奈米線混合方法。其中濕混法預期望藉由加入溶液減低奈米線間的碰撞力以預防斷裂情形發生。然而實驗結果顯示乾混與濕混之奈米線長度並無太大差異，且濕混法尚有奈米線沉積表面等分佈不均的情形。
以不同混合方法添加0.01wt%~0.1wt%銀奈米線及銀奈米粉末均不會影響晶體成長。若觀察臨界溫度轉換區間(∆T_c)，所有添加樣品均有擴大的情形，代表有部分的離子置換及固溶情形發生。此外，於擄磁性質部分，以濕混法添奈米線之樣品具有最佳的提升效果，優於乾混法及銀奈米粉末添加樣品。於臨界電流性質量測，可觀測到以乾混法添加銀奈米線在較低添加量時(0.05wt%以下)有較佳的性質，而濕混法添加銀奈米線則於較高添加濃度(0.05wt%以上)有較佳的表現。於釘扎力計算，可觀測到以乾混法添加銀奈米線較能提升高場下的釘扎力，其後依序為濕混法及銀奈米粉末。
本實驗建立之釘扎機制分析方法可得係數及曲線下面積兩種結果，分別代表釘扎中心尺寸/數量及釘扎機制佔有比例。而以此方法分析柱狀缺陷引入之文獻以及前人實驗結果皆能呈現Surface/line釘扎中心增加，符合文獻預期，證明本計算機制是可信的。
利用本實驗建立之釘扎機制分析方法分析奈米銀添加樣品，得添加銀奈米線確實能如預期提升surface/line釘扎中心尺寸/數量。相對於此，銀奈米粉末本身則能作為volume釘扎中心，提升volume釘扎中心數量。另外所有銀添加樣品之point釘扎中心數目皆有提升情形，推測可能為銀離子與YBCO晶體有離子置換的情形造成。

This study can be divided into two parts. The first part is mainly discussing the effect of silver additives in the YBCO superconductors on superconductor properties. In another parts, we cites the pinning mechanism model derived by Dew-Hughes and design an analyzing method to find out probable pinning mechanisms in YBCO bulk superconductors.

In first part, we try mixing superconductor precursor powder and silver nanorods with alcohol to avoid nanorods fracturing. In the results, length of nanorods between wet mixing (with alcohol) and dry mixing (without alcohol) are similar, but distribution of nanorods in powder with wet mixing are not evenly.

By observing results of surface morphology and trapped field distribution of YBCO, adding silver nanorods and nanopowder with concentration 0.01wt% to 0.1wt% will not affect grain growth. After adding silver, ∆T_c is slightly expanded so there may be ion replacement and solid solution of silver. Trapped field, critical current density and pinning force all increase after adding silver.

By our pinning mechanism analyzing method, we can know the trend of size and amount of pinning center with concentration and the main pinning mechanism in YBCO bulk. By using this method to analyze former studies, we can get the same results as their expectation. And by this method, we know that the main mechanism of nanorods is surface/line and that of nanopowder is volume.

[1] J. G. Bednorz and K. A. Müller, "Possible high Tc superconductivity in the Ba−La−Cu−O system," Zeitschrift für Physik B Condensed Matter, vol. 64, no. 2, pp. 189-193, 1986.
[2] M. K. Wu et al., "Superconductivity at 93 K in a new mixed-phase Y-Ba-Cu-O compound system at ambient pressure," Physical Review Letters, vol. 58, no. 9, pp. 908-910, 1987.
[3] 陳引幹, "零電阻時代的超導陶瓷," 科學發展, vol. 3月, p. 6~11, 2004.
[4] M. Tomita and M. Murakami, "High-temperature superconductor bulk magnets that can trap magnetic fields of over 17 Tesla at 29 K," Nature, vol. 421, no. 6922, pp. 517-520, 2003.
[5] K. Matsumoto and P. Mele, "Artificial pinning center technology to enhance vortex pinning in YBCO coated conductors," Superconductor Science & Technology, vol. 23, no. 1, p. 12, 2010.
[6] 黃士杊, "摻雜不同形貌氧化鋅對單晶粒超導體之影響," 國立成功大學材料科學及工程學系碩士論文, 2010.
[7] 劉倩如, "添加氧化鋅/二氧化鈦電紡絲於釔鋇銅氧超導塊材之影響," 國立成功大學材料科學及工程學系碩士論文, 2012.
[8] D. Dewhughes, "Flux pinning mechanism in type-II superconductors," Philosophical Magazine, vol. 30, no. 2, pp. 293-305, 1974.
[9] K. O. Heike, Commun. Phys. Lab., 1911.
[10] C. Micahel and P. Davor, "Introduction to superconductivity and high-Tc Materials," World Scientific 1-21, 1992.
[11] Y. Zhao, C. H. Cheng, and J. S. Wang, "Flux pinning by NiO-induced nano-pinning centres in melt-textured YBCO superconductor," Superconductor Science & Technology, vol. 18, no. 2, pp. S43-S46, 2005.
[12] Q. Li et al., "Interlayer coupling effect in high-Tc superconductors probed by YBa2Cu3O7-x/ PrBa2Cu3O7-x superlattices," Physical Review Letters, vol. 64, no. 25, pp. 3086-3089, 1990.
[13] C. P. Bean, "Magnetization of high-field superconductor," Reviews of Modern Physics, vol. 36, no. 1P1, pp. 31-+, 1964.
[14] I. G. Chen, J. Liu, R. Weinstein, and K. Lau, "Characterization of YBa2Cu3O7, including critical current density Jc, by trapped magnetic field," Journal of applied physics, vol. 72, no. 3, pp. 1013-1020, 1992.
[15] D. P. Norton, A. Goyal, J. D. Budai, and D. K. Christen, "Epitaxial YBa2Cu3O7 on biaxially textured nickel (001): An appproach to superconducting tapes with high critical current density," Science, vol. 274, no. 5288, p. 755, 1996.
[16] A. de la Cruz and A. Badı́a, "Analytical model for the levitation force between a small magnet and a superconducting cylinder in the critical state," Physica B: Condensed Matter, vol. 321, no. 1, pp. 356-359, 2002.
[17] 徐振洲, "單晶粒高溫超導體之磁浮性能研究," 國立成功大學材料科學及工程學系碩士論文, 1997.
[18] 郭晉辰, "高溫超導塊材與磁場相互作用力之研究," 國立成功大學材料科學及工程學系碩士論文, 1998.
[19] S. Yuh and E. Akihiko, "Crystal growth of bulk high-Tc superconducting oxide materials," Materials Science and Engineering, vol. 19, no. 1-2, pp. 1-86, 1997.
[20] P. Diko, M. Kaňuchová, X. Chaud, P. Odier, X. Granados, and X. Obradors, "Oxygenation mechanism of TSMG YBCO bulk superconductor," in Journal of Physics: Conference Series, vol. 97, no. 1, p. 012160, 2008.
[21] D. F. Zhou et al., "MgO buffer-layer-induced texture growth of RE-Ba-Cu-O bulk," Superconductor Science & Technology, vol. 25, no. 2, p. 7, 2012.
[22] 陳柏憲, "以厚膜晶種接種滲透法製程成長人工鑽孔Y-Ba-Cu-O單晶粒塊材之研究," 國立成功大學材料科學及工程學系碩士論文, 2015.
[23] P. Mele et al., "Incorporation of double artificial pinning centers in YBa2Cu3O7-δ films," Superconductor Science and Technology, vol. 21, no. 1, p. 015019, 2007.
[24] V. Pan et al., "Supercurrent transport in YBa2Cu3O7-δ epitaxial thin films in a dc magnetic field," Physical review B, vol. 73, no. 5, p. 054508, 2006.
[25] D. Agassi, D. Christen, and S. Pennycook, "Flux pinning and critical currents at low-angle grain boundaries in high-temperature superconductors," Applied physics letters, vol. 81, no. 15, pp. 2803-2805, 2002.
[26] M. Murakami, M. Morita, K. Doi, and K. Miyamoto, "A new process with the promise of high Jc in oxide superconductors," Japanese Journal of Applied Physics, vol. 28, no. 7R, p. 1189, 1989.
[27] C. Jooss, R. Warthmann, and H. Kronmüller, "Pinning mechanism of vortices at antiphase boundaries in YBa2Cu3O7-δ," Physical Review B, vol. 61, no. 18, p. 12433, 2000.
[28] L. Civale, "Vortex pinning and creep in high-temperature superconductors with columnar defects," Superconductor Science and Technology, vol. 10, no. 7A, p. A11, 1997.
[29] M. Daeumling, J. Seuntjens, and D. Larbalestier, "Oxygen-defect flux pinning, anomalous magnetization and intra-grain granularity in YBa2Cu3O7-δ," Nature, vol. 346, no. 6282, pp. 332-335, 1990.
[30] V. Maroni, Y. Li, D. Feldmann, and Q. Jia, "Correlation between cation disorder and flux pinning in the YBa2Cu3O7coated conductor," Journal of Applied Physics, vol. 102, no. 11, p. 113909, 2007.
[31] T. Haugan, T. Campbell, N. Pierce, M. Locke, I. Maartense, and P. Barnes, "Microstructural and superconducting properties of (Y1− xEux) Ba2Cu3O7− δ thin films: x= 0–1," Superconductor Science and Technology, vol. 21, no. 2, p. 025014, 2008.
[32] M. Murakami, "Key issues for the characterization of RE–Ba–Cu–O systems (RE: Nd, Sm, Eu, Gd)," Applied superconductivity, vol. 6, no. 2, pp. 51-59, 1998.
[33] W. Ting, T. Egi, R. Itti, K. Kuroda, and N. Koshizuka, "Advances in superconductivity VIII," ed: Springer, Tokyo, 1996.
[34] P. W. Chen, S. Y. Chen, I. G. Chen, and M. K. Wu, "Enhancement of peak effect in Y–Ba–Cu–O bulk materials by the addition of nano‐sized Sm2O3," Journal of the American Ceramic Society, vol. 95, no. 10, pp. 3109-3114, 2012.
[35] T. Michael "Introduction to superconductivity," McGraw-Hill, 1996.
[36] W. A. Fietz and W. Webb, "Hysteresis in superconducting alloys—Temperature and field dependence of dislocation pinning in niobium alloys," Physical Review, vol. 178, no. 2, p. 657, 1969.
[37] L. Civale et al., "Vortex confinement by columnar defects in YBa2Cu3O7 crystals: enhanced pinning at high fields and temperatures," Physical Review Letters, vol. 67, no. 5, p. 648, 1991.
[38] A. Chiodoni et al., "Understanding the role of heavy ion-irradiation induced surface columnar nanostructures through FESEM imaging," Physica C: Superconductivity, vol. 470, no. 19, pp. 914-917, 2010.
[39] A. K. Jha et al., "Controlling the critical current anisotropy of YBCO superconducting films by incorporating hybrid artificial pinning centers," Ieee Transactions on Applied Superconductivity, vol. 26, no. 3, p. 4, 2016.
[40] A. K. Jha et al., "Tailoring the vortex pinning strength of YBCO thin films by systematic incorporation of hybrid artificial pinning centers," Superconductor Science and Technology, vol. 28, no. 11, p. 114004, 2015.
[41] A. Goyal et al., "Irradiation-free, columnar defects comprised of self-assembled nanodots and nanorods resulting in strongly enhanced flux-pinning in YBa2Cu3O7− δ films," Superconductor Science and Technology, vol. 18, no. 11, p. 1533, 2005.
[42] J. MacManus-Driscoll et al., "Strongly enhanced current densities in superconducting coated conductors of YBa2Cu3O7–x+ BaZrO3," Nature materials, vol. 3, no. 7, pp. 439-443, 2004.
[43] B. Jayaram, S. Agarwal, C. N. Rao, and A. Narlikar, "Anomalously large Tc depression by Zn substitution in Y-Ba-Cu-O," Physical Review B, vol. 38, no. 4, p. 2903, 1988.
[44] M. Masato, Melt processed high-temperature superconductors. World Scientific, 1992.
[45] V. V. Moshchalkov, "Vortex matter in superconductors at extreme scales and conditions - A scientific program of the European Science Foundation," Physica C-Superconductivity and Its Applications, vol. 332, no. 1-4, pp. IX-XV, 2000.
[46] T. Hatano, A. Matsushita, K. Nakamura, Y. Sakka, T. Matsumoto, and K. Ogawa, "Superconducting and transport- of B-Y-Cu-O compounds - orthorhombic and tetragonal phases," Japanese Journal of Applied Physics Part 2-Letters, Article vol. 26, no. 5, pp. L721-L723, 1987.
[47] R. J. Cava, B. Batlogg, C. H. Chen, E. A. Rietman, S. M. Zahurak, and D. Werder, "Oxygen stoichiometry, superconductivity and normal state of YBa2Cu3O7-δ," Nature, vol. 329, no. 6138, pp. 423-425, 1987.
[48] T. B. Lindemer et al., "Experimental and thermodynamic study of nonstoichiometry in〈 YBa2Cu3O7‐x〉," Journal of the American Ceramic Society, vol. 72, no. 10, pp. 1775-1788, 1989.
[49] L. Byeong‐Joo and L. Dong Nyung, "Thermodynamic evaluation for the Y2O3–BaO–CuOx system," Journal of the American Ceramic Society, vol. 74, no. 1, pp. 78-84, 1991.
[50] 陳詩芸, "添加物對單晶粒釤鋇銅氧超導體微結構及釘扎特性研究," 國立成功大學材料科學及工程學系博士論文, 2003.
[51] Y. Peidong and C. M. Lieber, "Nanorod-superconductor composites: a pathway to materials with high critical current densities," Science, vol. 273, no. 5283, p. 1836, 1996.
[52] 陳柏偉, "滲透法及奈米添加物對Y-Ba-Cu-O超導體的超導性及微結構的影響," 國立成功大學材料科學及工程學系博士論文, 2012.