低价态锡氧化物的可控合成及电输运和铁磁性质研究

The presence of 5s2 lone pair electrons with stereochemical activity in Sn2+ ion led to unique structures of low-valence tin oxides, giving rise to novel electrical, magnetic, optical properties, and potential applications. Recently, much attention has been attracted on low-valence tin oxides due to the intrinsic p-type conductivity, the superconductivity of SnO and the mixed valence of intemediate tin oxides. However, the synthesis of low-valence tin oxides is very difficult due to the oxidation/disproportionation reactions of Sn2+ ion. Thus, the lack of high-quality samples restricted the understanding of intrinsic properties of low-valence tin oxides. In this project, we will synthesis low-valence tin oxides by a hydrothermal method, and focus on the study of their electrical, magnetic properties, and corresponding physical mechanism. The inherent relevance of tin oxidation state, crystal structure, electrical structure, electrical and magnetic properties of tin oxides will also be clarified. The lauching of this project will not only help to disclose the intrinsic properties of low-valence tin oxides with a better understaning of tin oxides and mixed valence system, but also help to push forward the application of low-valence tin oxides in the electrical and magnetic fields. In addition, it will provide reference for the controlled synthesis of other multiple-valence compounds.

Sn2+中存在具有立体化学活性的孤对电子5s2，使得低价态锡氧化物具有不同于SnO2的结构特征，将表现出新奇的电、磁、光性质，具有潜在的应用前景。近期SnO的本征p型导电，高压下的超导电性以及中间态锡氧化物的混合价态等都引起了人们对低价态锡氧化物的关注。然而由于Sn2+易发生歧化或氧化反应，低价态锡氧化物单相材料的合成非常困难。高质量样品的缺乏制约了人们对低价态锡氧化物本征性质的认识与理解。本项目拟通过水热法合成低价态锡氧化物，重点研究其电输运性质和磁性及其微观本质，阐明锡的氧化态与锡氧化物的晶体结构、电子结构和电磁性质的内在关联。本项目的开展具有重要的科学和应用价值，不仅有助于揭示不同氧化态锡氧化物的基本特性，加深对Sn-O体系、混合价态体系的认识，也将有助于推动低价态锡氧化物材料在电子学及磁学领域的实际应用，并可为其它多重价态化合物的可控合成提供借鉴。

锡离子的双重价态赋予了锡氧化物成分和结构的多样性。通过水热生长技术选择性合成不同氧化态的锡氧化物，掌握了水热法合成低价态锡氧化物关键技术（氧化还原调控技术和过饱和度控制技术）；针对锡氧化物二元体系的一些基础科学问题，开展了锡氧化物的晶体结构和电子结构表征、电输运和磁性、光学性质、稳定性及相变等研究；系统研究了SnO单晶低温下的结构变化及电输运性质，揭示了SnO单晶随温度的金属-半导体转变与低温下结构变化的关联性。. 同时为了比较研究，适当将研究工作拓展到多重价态金属（锡、铈）的氧化物薄膜，在柔性类单晶织构基底上采用化学和物理制膜法成功外延生长了织构良好的CeO2薄膜，揭示了沉积过程中的价态转化规律及生长机制。. 本项目揭示了不同氧化态锡氧化物的不同特性，加深了对Sn-O体系及其他多重价态体系的认识，将有助于推动多重价态化合物在电子学、磁学及光学领域的实际应用。.