The Preparation And Properties Researches Of Mg₃N₂ Powders

As a widely used semiconductor material,Magnesium nitride is an indispensable sintering aid in the solid state reaction for producing many new materials with excellent performance such as BN and Si₃N₄.For example,magnesium nitride can promote the transformation of hexagonal wurtzite BN into cubic sphalerite boron nitride under high temperature and pressure.Magnesium nitride can also be used to recycle nuclear fuel,manufacture special ceramic materials and special glass,and be used as an addictive in melting steels with high strength.Meanwhile,it is also one of the M-N-H(M refers to theⅠ.orⅣgroup and some transitional metals) material series of hydrogen storage,which are widely concerned in recent years.In addition,it is widely accepted that the band gap of magnesium nitride is about 2.8 eV.So it has potential use in both fabricating light-emitting diodes(LEDs) and laser diodes(LDs).Various methods are available in producing magnesium nitride,such as the direct reaction of magnesium powder and nitrogen gas,the direct reaction of magnesium powder and ammonia gas,the reaction of magnesium and nitrogen in nitrogen plasma, the explosion of magnesium coil in nitrogen atmosphere,and chemical vapor deposition under low pressure.The direct reaction of magnesium powder and nitrogen gas is suitable for mass production and the cost is relatively low.It is a method that has the value of industrial production,so we choose this method to produce the experimental samples.Magnesium nitride powders were produced by an one-hour reaction of magnesium powders and nitrogen gas under temperatures from 500℃to 850℃. By comparing these experiments,we find that the optimal condition for producing magnesium nitride is an one-hour reaction of magnesium powders and nitrogen gas under 750℃.Based on an investigation through X-ray diffraction(XRD) about the major ingredients and structure of magnesium nitride powders produced under 650℃-800℃,it is found that the samples produced under above-mentioned conditions are all high-purity magnesium nitride powders,the diffraction peak of which is compatible with the data on the PDF card.We tested the samples produced under an optimal condition by using Fourier transform infrared absorption spectroscopy(FTIR),and got the same finding as the experiment with XRD:the main high absorption peaks all come from magnesium nitride,and the main ingredient of the sample is magnesium nitride.Surface morphology of the samples produced under 650℃-800℃was measured by using scanning electron microscopy,and it is found that the samples take mainly a rod-like structure,the diameter of which is about 1μm,and the length of which increases with the boost of temperature.The crystal produced under low temperatures has better quality than that produced under high temperatures.In addition,it is found that there is a small quantity of nanometer-wire structure in the samples.Based on the study of the physical properties and thermal stability of magnesium and magnesium nitride powders by applying differential thermal analysis(DTA) and thermo gravimetric analysis(TGA),we found that when put in argon gas,Magnesium is beginning to melt at about 650℃,to gasify at about 700℃;when put in the air, Magnesium begins to burn at about 570℃;in nitrogen gas,magnesium reacts with nitrogen at about 630℃and the reaction is relatively slow;When heated in argon gas,the air and nitrogen gas,magnesium nitride did not display significant reduction in quantity and obvious heat exchange with the outside environment.The experiments indicate that magnesium nitride has very good stability in above-mentioned three kinds of gas below 1000℃.