Synthesis And Characterization Study Of Claringbullite And Barlowite

In recent years,magnetic geometric frustration systems have attracted much attention from condensed matter physicists because such systems provide a unique region for looking for new quantum states.The kagome lattice antiferromagnet with S=1/2 belonging to the magnetic geometry is one of the best materials to realize the quantum spin liquid.Quantum spin liquid means that even when the temperature drops to absolute zero,there is no way to produce magnetically ordered quantum states,since the system has a very strong quantum fluctuation.In contrast to conventional ferromagnetic and antiferromagnetic materials,quantum spin liquids have the promise to exhibit various novel properties,giving their realization in materials very attractive prospects.For example,quantum spin liquid is a typical topological ground state,which is expected to realize quantum computing in topological protection,which can be applied to national security,information technology,clean energy,healthcare,communication,and will have a significant impact on all aspects of our lives.In this paper,Cu₄（OH）₆FCl and Cu₄（OH）₆FBr with perfect kagome lattice are used as research objects,and Cu₄（OH）₆FCl and Cu₄（OH）₆FBr samples are prepared by hydrothermal method and solvothermal method.The possible ways to control morphology and size of the sample were investigated by controlling the reaction time,temperature,solvent,surfactant,etc.,combining with data from powder X-ray diffraction and scanning electron microscopy.The Cu₄（OH）₆FCl and Cu₄（OH）₆FBr samples prepared under optimal conditions were characterized by transmission electron microscopy,infrared absorption spectrum,Raman scattering spectrum,ultraviolet absorption spectrum and magnetic properties.The main research results are as follows:（1）Cu₄（OH）₆FCl was synthesized by hydrothermal method.By adding different surfactants,changing the time and temperature,the optimum conditions for the synthesis of Cu₄（OH）₆FCl were determined,namely using copper chloride dihydrate and sodium fluoride as raw materials,adding surfactant hexamethylenetetramine,reaction temperature 175℃,reaction time 2 hours.Pure Cu₄（OH）₆FCl cannot be prepared by solvothermal method.Through powder X-ray diffraction and EDS spectroscopy,we confirmed that the sample synthesized in our experiment is Cu₄（OH）₆FCl,belonging to the hexagonal crystal,and the space group is P6₃/mmc.The morphology of Cu₄（OH）₆FCl crystal is regular hexagonal with side length between 100 nm-600 nm under the optimal experimental conditions.The structure and bonding properties of Cu₄（OH）₆FCl were studied by infrared absorption spectroscopy and Raman scattering spectroscopy.The ultraviolet-visible absorption spectrum showed that the direct band gap of Cu₄（OH）₆FCl was 3.2 eV.The magnetic properties of Cu₄（OH）₆FCl samples were tested by superconducting quantum interference analysis system.Cu₄（OH）₆FCl exhibited antiferromagnetic phase transition at T_N=16.01K and weak ferromagnetism at low temperature.（2）We successfully prepared Cu₄（OH）₆FBr samples by hydrothermal method.We tried to change the reaction time and temperature in the experiment,and finally determined that the best reaction temperature for the preparation of Cu₄（OH）₆FBr was175℃and the reaction time was 2 hours.The sample is confirmed to be Cu₄（OH）₆FBr,belonging to hexagonal crystal and space group P6₃/mmc by powder X-ray diffraction and EDS analysis.By SEM and TEM analysis,the morphology of the crystal is similar to that of Cu₄（OH）₆FCl,with regular hexagonal shape and side length of about 1μm.The bonding and vibration modes of Cu₄（OH）₆FBr were analyzed by infrared absorption spectroscopy and Raman scattering spectroscopy.The magnetic properties of Cu₄（OH）₆FBr samples were studied by M（T）and M（H）curves.The antiferromagnetic phase transition of Cu₄（OH）₆FBr at T_N=15 K was observed.At low temperature,there are obvious hysteresis loops,indicating weak ferromagnetism,which may be because the Jahn-Teller effect destroys the cage structure of Cu₄（OH）₆FBr,resulting in lattice distortion.