Synthesis And Characterization Of New Iron Fluorophosphate And Manganese Fluoride Compounds

In recent years,transition metal fluorophosphate materials composed of fluorophosphate chain polyhedron structures have been widely used in many fields.Mixed anionic fluorophosphate compounds have become one of the research hotspots in structural chemistry,electrochemistry and other fields because of their rich and diverse chemical structures,electronic structures and excellent magnetic properties.Low dimensional transition metal compounds have higher research value due to their unique properties such as magnetic anisotropy and electronic phenomena.Transition metal fluoride materials also have important physical properties,such as magnetoresistance,multiferroity,ferroelectricity,magnetoelectricity and nonlinear optical behavior.Although there are currently various synthesis strategies,the synthesis of new transition metal fluorine materials remains a challenge.In this thesis,three new barium Fluorophosphoric acid salts and two new Manganese（II）fluoride materials were synthesized by hydrothermal reaction for transition metal compounds,and their structures were analyzed and characterized.The main research content is as follows:1.Three fluorinated phosphates and fluorophosphates were synthesized through a fluorine-rich hydrothermal reaction,with the chemical formulas Ba₃Fe（PO₄）F₆,Ba₃Ga(PO_3.5F_0.5)O_0.5F_5.5 and Ba₃Fe（PO₃F）F₇ respectively.In this series,the first two belong to isomorphic compounds,and their three-dimensional structure consists of[M(PO_4-x)F₄]^4-x chains and two-dimensional[Ba₃F_2-xO_x]^4+x layers[M=Fe,Ga;x=0,0.5],while the three-dimensional structure of Ba₃Fe（PO₃F）F₇ is composed of a two-dimensional[Ba₃F₂]⁴⁺layer containing twists and a[Fe（PO₃F）F₅]^4-dimer.Among them,the two-dimensional[Ba₃F₂]⁴⁺layer is formed by a tetrahedron centered on fluorine.Studies of bond lengths and bond strengths of tetrahedral complexes centered on fluorine atoms verify the stable structural properties of fluorine-centered tetrahedra.Not only that,this series of fluorophosphates synthesized by fluorine-rich hydrothermal reaction also demonstrated diverse structural features and chemical properties.2.Two Novel open skeleton manganese fluoride compounds,Ba₃Mn₃F₁₄ and Ba₃Mn₄F₁₈were prepared through mild hydrothermal reactions.It expands the category of open skeleton compound materials,and also verifies the effectiveness of mild hydrothermal method in the preparation of mixed valence manganese Fluorine compounds.The crystal structure of Ba₃Mn₃F₁₄contains chains structure consisting of separate edge-shared Mn^IIF₆trigonal prisms and corner-shared Mn^IIIF₆ distorted octahedral.However,Ba₃Mn₄F₁₈consists of two-dimensional_∞[Mn₃F₁₄]^6-sheets,formed by corner-shared Mn^IIIF₆octahedra.Magnetic studies have led to the conclusion that the ground states of Ba₃Mn₃ F₁₄and Ba₃Mn₄F₁₈ are both AFM（Antiferromagnetism）,and both have the nature of predominantly antiferromagnetic interactions with a weak ferromagnetic contribution.The hysteresis phenomenon in Ba₃Mn₃ F₁₄ and Ba₃Mn₄F₁₈ crystals is significant,and the spin-flip transition occurs when the magnetic field is increased,and the magnetic moments are progressively rotated.This research work further confirmed the structural diversity of open skeleton compound materials,and at the same time,the crystal structure analysis of both laid a theoretical foundation for further exploring the physical and chemical properties of this kind of open skeleton materials.