Synthesis, Growth And Characterization Of Novel Chalcogenides

Chalcogenides are some kind of inorganic compounds which have many types of structure, lots of different physical properties and a large quantity. These compounds have important applications in the fields of nonlinear optics, catalysis, solar energy, infrared optics, thermoelectric, photoelectric, fiber, battery and ion conductor materials. The synthesis and properties of chalcogenides have attracted wide concern.So far, little research has been conducted in the new chalcogenides LiGa3Te5and Li4P2Se6. For LiGa3Te5, only crystal structure and basic physical properties of polycrystalline powders have been reported. There haven’t been any studies on bulk LiGa3Te5crystal growth and its crystal properties. As for Li4P2Se6, there have not been any reports on its crystal structure and properties until now. In this thesis, solid phase synthesis of LiGa3Te5and Li4P2Se6, growth and basic characterization of LiGa3Te5crystals, and crystal structure of Li4P2Se6were studied. The main contents were as follows:1. Solid phase synthesis of LiGa3Te5and Li4P2Se6The solid phase synthesis of LiGa3Te5and Li4P2Se6were studied in detail. For LiGa3Te5, a two-step method was proposed. At first we synthesized Ga2Te3, then used Ga2Te3, Li and Te to synthesize LiGa3Te5. Graphite crucibles with raw materials were putted into high-pressure autoclave and quartz tube. We found that synthesizing in quartz tube was easier to get pure polycrystalline LiGa3Te5. Thermal properties of polycrystalline LiGa3Te5were measured by TGA/DSC and these properties were the basis for the crystal growth. For Li4P2Se6, different synthesis conditions were tried. The optimum conditions included temperature, reaction time, mole ratio of materials were500℃,20hours, Li:P:Se=4:2.1:6. Finally we successfully got small yellow Li4P2Se6crystals for characterization of its structure.2. Crystal growth of LiGa3Te5Vertical Bridgman-Stockbarger Method was used to grow LiGa3Te5crystals. The furnaces were designed and made by ourselves. Growth technology of LiGa3Te5crystals was explored by changing the crucible, temperature gradient, speed of crucible descending and crystal rotation. Finally the proper technological parameters were got and bulk LiGa3Te5single crystal was obtained.3. The basic physical properties of LiGa3Te5crystalThermal properties of LiGa3Te5crystal were studied. The melting point was783.27℃. The specific heat increased from0.263J/(g·K) to0.343J/(g·K) as the temperature rising from300℃to410℃. The transmission spectrum of LiGa3Te5was measured. The result showed that LiGa3Te5crystal had a wide spectral transparency range (from1.4μm to22μm), so LiGa3Te5may be used for infrared coatings and infrared windows.4. The crystal structure of Li4P2Se6To get the crystal structure of Li4P2Se6, single-crystal X-ray diffraction data was collected. Li4P2Se6crystallizes in orthorhombic, space group Pnma. The crystal cell parameters are a=13.910(16) A, b=11.248(13) A, c=6.476(7) A, α=β=γ=90°, V=1013(2)A3, Z=4.