The Study On The Structural Characteristic And Physical Properties Of Nano-micro Iron Sulfide

To study different structure and physical properties of the iron sulphide under heat vulcanization in this paper,we have integratly used polycrystalline X ray diffraction(XRD),transmission electron microscopy(TEM),power tester(YHZ-1106),UV-VIS-NIR spectrophotometer,vibrating sample magnetometer(VSM)and other modern test methods to study the morphology,composition,structure and hermal-coefficient,optical absorption properties and magnetic properties of the synthesis of pure pyrite,doped pyrite and pyrrhotite,in order to through the analysis of the influence of crystal structure,chemical composition and other factors on the physical properties,to try to reveal the relationship between response of crystal structure on the physical properties of materials.The work and conclusions of this paper are as follows:(1)The pyrite with high purity was prepared by thermal curing at 320-400?.The size of the sample is obviously influenced by temperature,and increases first and then decreases.The temperature of sulfide has different effects on morphology,size and chemical composition of pyrite crystal.There are different densities in Pyrite different crystal orientations,the higher density,the more the corresponding point defects,thus has a significant effect on thermoelectric coefficient value of the sample.The influence of the low index diffraction crystal surface((111),(200)and(210))on the thermal coefficient of pyrite is obviously higher than the high index diffraction planes((220)and(311)).(2)The light absorption properties of pure pyrite were also studied.We found there are three similar absorption region:(weak absorption area,linear absorption area and energy absorption area)in light absorption curve of pyrite under different temperatures.The absorption coefficient at 360? is the maximum,reaching 4.25*105cm-1.The light absorption coefficient of sample are greatly influenced by temperature,firstly increases with the rise of the temperature,at 360? to maximum,and then decrease with the temperature.Temperature,grain size and S/Fe ratio have a certain influence on light absorption coefficient and forbidden band width.Analysis mainly is the grain size firstly increases and then decreases with temperature increase.The finer grain size,the more the light through the gaps between the grains,and thus affect the efficiency of light absorption.Grain refinement can cause more defects such as grain boundary.S/Fe ratio changes reflect defects such as internal clearance of the sample,and both can cause additional acceptor or donor level formed in crystal,thus cause the change of the forbidden band width.(3)The crystal structure,morphology,grain size,chemical composition and optical absorption properties of different content of Co and Ni doped pyrite were studied,we think that Co and Ni doping does not change cubic crystal type,but a certain influence on the crystallinity,affecting the morphology appearance of the sample;Doped Co lead to crystallization degree of variation,the agglomeration of coarse grain;Ni doping will cause sample grain refinement The ratio of S/(Fe+Co)was within the rang of 1.92 to 2.05,the greater the degree of deviation of the ratio of 2 show that the more internal point defect,the more will affect the light absorption performance.Ni doped samples also appear similar situation.The optical absorption curves of all the doped samples show the characteristics of the semiconductor.The band gap of Co doped is roughly between 0.57eV-0.72eV,and the band gap firstly decreases(Co-3 at.%)and then increases(5-9at.%Co).Because with the increase of amount of doped Co,more point defects generated within the sample,the formation of additional level reduced band gap;The phase appear trace CoS2,resulting in the band gaps of the samples increased.Ni doped samples have similar conditions.However,the band gap of Ni doped 7at.%sample is the largest.Width of the forbidden band width in theory is helpful to improve the theory of the photoelectric conversion efficiency.(4)The crystal structure,micro-structure and magnetic properties of sample under the conditions of thermal sulfur are also considered:the structure of the sample is greatly affected by temperature.At 360? and 380?,the phase transformation occurs from the pyrrhotite to the cubic FeS2.At the 400?,the sample was generated at a high temperature of hexagonal system system variant of Fe7S8.The effect of temperature on the morphology of the sample is also large.Overall,The magnetic energy of sample at 320?is optimal,at 300?and 340? are second,and 400? is poor.