使用雙鍍源熱蒸鍍冷凝法製作銦與錫的奈米顆粒樣品,經由X光繞射譜圖以及TEM影像分析,樣品為β-In3Sn@In/γ-InSn4@Sn核殼結構奈米顆粒樣品,β-In3Sn核的粒徑為14 nm,In殼層的厚度為5.5 nm,超導臨界溫度為5.65 K;γ-InSn4核的粒徑為37 nm, Sn殼層厚度為3.4 nm,超導臨界溫度為5.37 K;銦的超導臨界溫度為2.84 K,與塊材相比降低約17%,這是由於量子尺寸效應的影響所導致。交流磁化率對溫度的關係圖中,在3 K與5.5 K附近都有明顯的轉折變化,這是因為顆粒核心與外殼的超導臨界溫度不同,並且兩種顆粒核心的超導溫度皆大於銦殼層或錫殼層,以至於會出現外殼層為正常態,核心為超導態的特殊情況發生。提高壓合密度後,顆粒的磁矩μ_p隨著下降,推測這是由於顆粒間的交互作用增強,使得表面與內部電荷重新分佈所造成。飽和磁化強度隨壓合密度上升而增強,是因為顆粒間距離縮短,磁矩密度增加所導致。
The nanoparticles were fabricated employing the gas-condensation method, using a chamber equipped with two decoupled evaporation sources for separate evaporation of In or Sn. XRD patterns and TEM images is utilized to determine the mean particle diameter, size distribution of the powder and nano-sized core@shell structure of β-In3Sn@In/γ-InSn4@Sn. 14 nm/37 nm is diameter ofβ-In3Sn/γ-InSn4, 5.5 nm/3.4 nm is thickness with In/Sn. 5.65 K/5.37 K/2.84 K is critical temperature ofβ-In3Sn/γ-InSn4/In.
The superconducting and magnetic properties are studied by AC magnetic susceptibility and magnetization measurements, in which magnetic properties and superconductivity are observed. The AC magnetic susceptibility has an inversion at 3 K, because the critical temperature is difference on core and shell. Magnetic hysteresis increase dependent on temperature cooling or packing fraction increasing.
[1] W. Meissner and R.Ochsenfeld,Naturwiss,21(1993),787
[2] J. Bardeen, L. N. Cooper and J. R. Schrieffer, Phys. Rev. 108, 1175 (1957)
[3] F. London, H. London, Physica 2, 34 (1935); Proc. Roy. Soc. (London) A 149, 71 (1935)
[4] 張裕恒,李玉芝,超導物理,儒林圖書公司(1997)
[5] N. W. Ashcroft, N. D. Mermin, Solid State Physucs (1976)
[6] 何鈞考,錫奈米微粒的超導參數與自旋極化,中央大學碩士論文 (2006)
[7] B. Mühlschlegel, D. J. Scalapino, R. Denton, Phys. Rev. B 6, 5
(1972)
[8] C. Luef et al., Intermetallics 13, 1207–1213 (2005)
[9] A. C. Gandhi et al., Supercond. Sci. Technol. 25 (2012)
[10] 王進威,擬合 X 光繞射峰形判定奈米微粒粉末的粒徑分析, 中央大學碩士論文 (2006)
[11] 許樹恩,吳泰伯,X 光繞射原理與材料結構分析,國科會精儀中心 (1993)
[12] 徐健綱,PbPbO暨Sn奈米顆粒聚合體的超導及磁性探討,中央大學碩士論文 (2003)
[13] S. Mørup, B. R. Hansen, Phys. Rev. B 72, 024418 (2005)