新型过渡金属化合物的氧化还原制备、多维复杂结构与磁电性能

In recent years there has been considerable interest in layered compounds which exhibit the phenomena of special coordination and mixed valence. Experience shows that new materials with strongly correlated electronic properties which share the common feature of interplay among spin, charge and orbit degrees of freedom may be tuned by changing e.g., the crystal structure, chemical composition, degree of disorder and external strain through the unstable region, leading to dramatic change in properties. However, the preparation method is old, new structure type is lack, and the scope the of investigation is narrow as for multi-dimensional transition metal oxides and derivatives associated with electron correlation effects. The object of this project is to synthesize the new transition metal oxides and derives, where flux technology including different redox species, low temperature reduction with metal hydrides and fluorinated methods will be preformed. Detailed crystal structur will be invesitigated by synchrotron and neutron powder diffraction experiments.Chemical analysis, corrdination, cationic valence, magnetic structure, electronic structure, electronic, magnetic and heat properties will aslo be evaluated. These studies are expected to investigate the cooperative relationships amongst transition metal ions. The beauty of art will enables us to not only uncover the cooperative relationships between micro parameters including,bond angles, bond lengths, valence, spin state etc and macro-properties such as electronic,magnetic and heat properties but also disclose a variety of important phenomena including metal-insulator transitions, sharp crossovers driven by variation of critical structural microparameter (i.e bond, valence). We expect that new magnetoresistance, pure inogranic mocular magnet, magnetic refrigeration, superconductor materials would be found after fine-tuned the competing electronic interactions driven by variation of temperature, magnetic field, chemical composition and other variables in the metastable phases containing layered or chain-like structure of transition metal species launched by anions-centred, and monitored the detailed the structure in the large scientific facilities simultanously.

特殊配位多型体，混合价态的层状结构化合物是当今高新技术材料设计的热点。经验表明，温度、压力、磁场、晶格畸变、化学压应变等宏观参数在相变点处的微小变化将导致自旋-电荷-轨道多自由度的强关联体系中电子相发生显著地变化，最终极大地影响性能。但是与电子强关联效应相关的多维过渡金属氧化物及其衍生物的制备方法陈旧，结构类型单一，研究范围窄。拟利用不同氧化还原介质的新熔盐技术，低温金属氢还原与氟化方法合成新化合物，通过同步辐射、中子衍射等手段精细解析晶体、磁结构，测量磁、电、热学性能，综合化合价、化学键等信息，建立过渡金属离子经由化学键产生的磁相互作用机制，相变点附近的微观结构参量变化与性能转变之间的关联。希望能够根据认识角度的转换与亚稳相的设计思想制备出多种过渡金属功能基元片层或链状结构的亚稳相，在相变点附近进行温度、磁场、化学压应变调控并依托大科学装置发现几种磁阻、纯无机分子磁、磁制冷、超导材料。

特殊配位多型体，混合价态的层状结构化合物是当今高新技术材料设计的热点。经验表明，自旋-电荷-轨道多自由度的强关联体系中电子相发生显著地变化，最终极大地影响性能。但是与电子强关联效应相关的多维过渡金属氧化物及其衍生物的制备方法陈旧，结构类型单一，研究范围窄。本课题利用不同氧化还原介质的水热，新熔盐技术，低温金属氢还原与氟化方法合成大量新型化合物。围绕过渡金属离子的价态，化学键，过渡金属功能基元结构与化合物电、磁性质之间的关联展开研究，通过最先进的手段，如穆斯堡尔谱，中子衍射，同步辐射衍射，µSR等分析了重要化合物，按计划开展了磁相互作用机制，磁性基态等方面的研究，并取得了具有重要科学意义的研究成果。..1、制备了一系列过渡金属氟磷酸盐。BaxFex(PO4)Fy的磁学表征揭示了不同的磁性：x=1是S=5/2 自旋链，x=2存在Fe2+和Fe3+ 的表现出倾斜反铁磁性，x=3为耦合的自旋三聚体。Ba2M2PO3F7表现出反铁磁行为，形成了锯齿形一维链。.2、合成了12种硒碲氧酸盐，其中发现了锂电固体电解质材料Li3FeTe4O11；在过渡金属氟硒氧酸盐中，发现了具有近藤晶格反铁磁的Mn以及二维磁性立方晶格的Fe。 .3、 在合成的过渡金属四元化合物中，发现了新颖的结构及特性：在Co化合物中Te(IV)孤对电子被封闭在五角十二面体空腔中，在M2(SeO3)F2中罕见的O-O和F-F交替µ2桥的1D链会产生圆滚线型（Mn）和自旋倾斜（Co）磁结构，带有蜂窝晶格和一维四边形链特征的Cu化合物低温失去反铁磁性。.4、还利用多种过渡金属化合物与其他材料复合的办法研究了锂离子电池阳极材料，储能电容器材料。..我们发现重要化合物中的过渡金属阳离子都是与两个的阴离子配体结合形成异形多面体。不同的阴离子特性增加了新的电子维度，发现了单阴离子类似物无法实现的现象。