Mechanochemistry of Oxide and Fluoride Nonequilibrium Phases: Mechanosynthesis, Solid State Kinetics and Spectroscopic Properties

该项目涉及新的晶态氧化物和氟化物非平衡相的直接机械力化学合成和结构表征。第一阶段主要研究钙钛矿、橄榄石、石榴石、萤石和尖晶石结构的结晶体系，第二阶段将研究扩展到更复杂的材料，如(I)具有莫来石型结构的氧化物，其总组成为Bi2X4O9/10(X=Ga3+，Fe3+，Al3+，Mn3+，Mn4+)，(Ii)辉石型化合物，如含锂辉石LiYSi2O6(Y=Fe3+，Al3+，Cr3+)，和(Iii)Li2ZSiO4系列氧化物(Z=Fe2+，Mn2+，Co2+，Ni2+)。此外，还将研究其他氟化物系统，如BaSnF4，BaMgF4，以及基于SnF2的亚稳复合材料。关于第一阶段研究的几个系统的亚稳结构构型的复杂问题，将与面向理论的小组合作处理。主要重点将放在亚稳态化合物形成的机制和动力学的研究上，包括对其热稳定性的研究，特别是其局域原子和电子结构的研究。首先，将使用核磁共振和穆斯堡尔谱学等补充核方法，这些方法允许跟踪制备相的松弛路径，直到局部尺度上的平衡态和相关的动力学。除了确定非平衡相的局域结构外，动力学、电学和磁学性质的研究是该项目的第二优先事项。该项目将有助于理解支配机械合成非平衡相形成机制的结构形成因素，以便以定向的方式操纵它们以合成新的功能材料。

The project deals with the directed mechanochemical synthesis and structural characterization of new crystalline oxide and fluoride non-equilibrium phases. While in the first period mainly systems crystallizing with the perovskite, olivine, garnet, fluorite, and spinel structure were investigated, in the second period, the research will be extended to more complex materials such as (i) oxides with the mullite-type structure with general composition Bi2X4O9/10 (X = Ga3+, Fe3+, Al3+, Mn3+, Mn4+), (ii) the pyroxene-type compounds, e. g., Li-containing pyroxenes LiYSi2O6 (Y = Fe3+, Al3+, Cr3+), and (iii) the Li2ZSiO4 family of oxides (Z = Fe2+, Mn2+, Co2+, Ni2+). Also other fluoride systems like BaSnF4, BaMgF4, and metastable composites based on SnF2 will be investigated. Complex problems regarding the metastable structural configurations in several systems investigated in the first period will be processed in cooperation with theoretically-oriented groups.The main focus will be given to the investigation of the mechanisms and kinetics of the formation of metastable compounds involving studies concerning their thermal stability, especially their local atomic and electronic structures. Primarily, complementary nuclear methods such as NMR- and Mössbauer spectroscopy will be used, which allow to follow the relaxation paths of the as-prepared phases to the equilibrium state and associated kinetics at the local scale. Besides the determination of the local structure of the non-equilibrium phases the investigation of the dynamic, electric and magnetic properties is the second priority of the project. The project shall contribute to an understanding of the structure-forming factors which govern the formation mechanisms of the mechanosynthesized non-equilibrium phases, in order to manipulate them in a directed way for the synthesis of new functional materials.