Synthesis,Characterization And High Pressure Study Of Metal Hydroxyfluoride MOHF(M=Zn,Cu)

In recent years,metal hydroxyfluorides have been widely used in the development of new functional materials,due to a simple and many synthetic routes,easy control of morphology,strong oxidation resistance,stable presence in the air,and a unique electronic energy band structure.Generally metal hydroxyfluorides are wide bandgap semiconductors and tend to form a layered structure with a large specific surface area.Therefore,it has widely application prospects in the fields of optoelectronic devices,photoluminescent materials,selective oxidation catalysts,degraded organic and inorganic dyes.Therefore,it is great significance for us to extensive and deeply research on metal hydroxyfluorides.In particular,pressure,which is a fundamental thermodynamic variable determining the properties of materials,can influence the microscopic structure,the interatomic electrostatic interactions,the electronic orbitals and the chemical bonding and even the formation of new high-pressure phases.High pressure studies of metal hydroxyfluorides can explore its new properties,new phenomena,and new structures.Provide experimental and theoretical support for the further widely used of metal hydroxyfluorides.In this thesis,zinc hydroxyfluoride and copper hydroxyfluoride nanomaterials are synthesized via a hydrothermal strategy.Its structure and physical properties were characterized and analyzed;the in-situ high-pressure synchrotron radiation X-ray diffraction was used for the high pressure research of the synthesized ZnOHF.The main research results are as follows:?1?Orthorhombic ZnOHF is synthesized via a hydrothermal strategy.Powder X-ray diffraction studies confirm that the prepared samples have a diaspore-type structure.According to the EDS analysis,the O/F ratio in equimolar proportion indicates the nearly perfect stoichiometry.The morphological featuresobserved via SEM and TEM techniques reveal that the product is composed of micro/nanometer-scaled prism-like structures.The band gap estimated from UVevis absorption measurements is 3.15 eV.The PL emission band is located at 470 nm.?2?Copper hydroxyfluoride powder was successfully prepared by hydrothermal method.The morphology of the sample was observed by SEM and TEM.The results showed that the prepared sample was a sheet-like structure,and its growth mechanism was studied in combination with its microscopic crystal structure.Measurements by Raman and infrared spectroscopy show that the vibrational frequency of hydroxyl groups is affected by hydrogen bonding.The UV-visible absorption spectrum measurements showed that the energy gap was about 3.9 eV.The hysteresis loop at room temperature was measured by a vibrating sample magnetometer.In addition,PPMS was used to measure the magnetic susceptibility in the 2-400 K temperature range.VSM measurement showed that it was soft magnetic at room temperature,and the PPMS measurement result showed that antiferromagnetic at low temperature and Neel temperature of 16 K,the results of the two can be mutually supportive.Its thermal weight test showed that it decomposed into copper oxide and hydrogen fluoride at around 365 degrees.?3?The compression behaviors of the as-prepared ZnOHF samples are investigated by using in situ high pressure angle dispersive synchrotron radiation X-ray diffraction techniques.The compression behaviors are characteristic of continuous topology evolution.The pressure-induced shearing reduces the symmetry of ZnOHF from the initial space group Pnma to its subgroup Pna2₁ in the pressure range of 14.2-19.8 GPa.The hints of a further phase transformation to the CdOHF-type structure at 30.7 GPa are also observed.