Hydrothermal Synthesis And Magnetic Properties Of New Transition Metal Fluorophosphate With Low-dimensional Features

The transition metal fluorophosphates have become widely used in materials science and chemistry due to their rich structural chemical properties and their practical or potential wide application value in many fields such as ion adsorption,catalysis,ion exchange and ion conductor,making it become one of the research hotspots in many fields such as materials science and chemistry.This article aims to explore the synthesis of new transition metal fluorophosphate,and to study its composition,structure and performance.This thesis aims to explore the synthesis of new transition metal fluorophosphate,and to characterize their composition and structure,and to explore their properties.In this content,five new compounds with two series were synthesized by hydrothermal synthesis method,using hydrazine hydrate to adjust PH.The crystal structure of the new compounds was determined by powder and single crystal X-ray diffraction techniques.The crystal morphology of the compounds was observed via the scanning electron microscope.The thermal stability was analyzed by thermogravimetric analysis.The functional group of the compound was determined by Fourier infrared spectrometer.The valance of transition metal anions was confirmed by EPR,XPS and M?ssbauer spectroscopy.The magnetic properties of the compound were measured by a superconducting quantum interferometer or VSM.The details as follows:1.In Ba_xFe_x?PO₄?F_y?1?x?3,2?y?12?system,Ba Fe PO₄F₂?I?Ba₂Fe₂PO₄F₆?II?and Ba₃Fe₃PO₄F₁₂?III?were synthesized by optimizing hydrothermal synthesis conditions:.I consisted of two-dimensional[Fe?PO₄?F₂]^2-sheets built from linear_?[Fe₂O₆F₄]^10-moieties formed by fluorine corner-sharing Fe O₄F₂and Fe O₂F₄octahedra with linking PO₄tetrahedra.Mixed-valence II possessed a three-dimensional framework containing Fe₄O₆F₁₂tetramers formed by the edge-sharing oxygen or fluorine atoms of cis-Fe F₄O₂octahedra.III contained 1D columns of_?[Fe₃?PO₄?F₁₂]^6-infinite sections built from cis-Fe F₄O₂and Fe F₅O octahedra and tetrahedral PO₄linkers.The magnetic characterization of Ba_xFe_x?PO₄?F_yunveiled diverse magnetism:an S=5/2 spin chain for I,a weak ferrimagnet or canted antiferromagnet for II thanks to the presence of distinct Fe²⁺and Fe³⁺sites identified by M?ssbauer spectroscopy,and coupled spin-trimers for III.2.Twoopen-frameworktransitionmetalfluorophosphates?NH₄?M₃?PO₃F?₂?PO₂F₂?F₂?M=Mn?IV?,and Co?V??have been synthesized under fluoride-rich hydrothermal conditions.The isostructure consists of triplets of face-sharing trans-MO₄F₂octahedra linked by PO₃F groups to form 2D layers,which featured transition metal layers with a staircase Kagoménetwork.These 2D layers are bridged by PO₂F₂groups to generate a 3D open framework with 1D channels filled with ammonium cations.The XPS spectra suggested the existence of Mn?II?and Co?II?in the corresponding compounds.Further,the XPS F 1s spectra indicated that fluorine anions bridged both the M and P centres.The magnetic measurements for each compound indicate Curie–Weiss behaviour,confirming the presence of high-spin Mn²⁺or Co²⁺ions and antiferromagnetic interactions.However,a weak ferromagnetism at low temperature?T_c=8.0 K for Mn and T_c=9.2 K for Co?was simultaneously observed,which can be explained by a canted antiferromagnetic ground state.