小分子嵌入高溫超導體衍生物之化學合成與特性鑑定之研究

Abstract

本研究之主旨在於探討鉍系鉍-2212 高溫超導體分別與小分子客體氨和平 面分子客體 pyridine 的嵌合化學及衍生物的基本特性鑑定. 本研究藉由 氣體反應法, 真空封管法和溶液迴流法等三種方法, 得到超導臨界溫度( Tc)為 93K 的氨嵌入產物與 Tc 為 90K 的 pyridine 產物.經由晶格常數 的估算可以推論出氨及 pyridine 的嵌入反應分別造成宿主晶格沿 c 軸 方向不同程度的增長. 經特性鑑定與分析, 可以證實氨及 pyridine 嵌 入所造成的部分電荷轉移現象是超導臨界溫度值提升的主因. 在本研究中 探討了嵌入反應所使用的反應方法, 並推論嵌入產物所可能的晶格結構, 以合理地解釋在鉍-2212 嵌入反應中所觀察到的超導臨界溫度變化現象; 證實經由嵌入反應可以改變高溫超導體的電子結構, 達到有效影響超導臨 界溫度的目的. The main purpose of this research is to investigate the intercalation chemistry of Bi-2212 superconductors with small moolecules and to characterize the intercalates derived from high-Tc Bi-2212 and ammonia or pyridine molecules. Intercalates have been prepared by employing gas-solid, evacuated seal-tube or solution-reflux type of reactions. On the Other hand, various degrees of the expansion in the crystallographic c-axis of the Bi-2212 have been observed in both ammonia- and pyridine- intercalated species based on the analysis of variations of the lattice constant. The enhancement of superconducting transition temperature (Tc) determined by electrical resistivity and magnetization measurements in both ammonia- and pyridine- intercalated species has been attributed to the partial charge transfer based on the characterization results. In this research we have explored the techniques employed in the intercalation reactions, deduced the possible structure of the intercalates, and rationalized the variation in superconductivity in the host. We have also demondtrated that chemcal intercalation is an effective route in systematic modification of electronicof high-Tc superconductors.