Preparation And Optical Properties Of Magnesia-alumina Spinel Transparent Ceramics And Glass Ceramics

Magnesium-aluminum spinel transparent ceramic is an excellent mid-infrared material,Which has a wider range of transmission than sapphire and AlON transparent ceramics.However the manufacturing cycle of single crystal sapphire is long,and the preparation temperature of AlON transparent ceramics is highly,all of which increases the economic cost of sapphire and aluminum oxynitride transparent ceramics,which is not conducive to its popularization and application.Magnesium aluminate spinel is a good alternative materials,due to the raw material is cheap,cubic crystal system structure make it is optical isotropic,it has high transmittance in the visible light region to the far infrared area,good thermal shock stability,resistance to chemical corrosion and wear resistance,high melting point,high hardness,make it widely used in the infrared window,bulletproof window,spacecraft protective window and submarine infrared sensors,and other fields.In order to obtain transparent magnesia-alumina spinel ceramics with good transmission,the preparation process must be strictly controlled to obtain a sample having a low porosity,a small crystal grain size,a high density and a high transmittance.In this research,nano-scale?-Al₂O₃ and nano-spherical MgO are used as raw materials,the ratio of Al₂O₃:MgO is 1.03,and 1wt%of LiF is added as sintering aid.The magnesium-aluminum Spinel transparent ceramic is prepared by hot pressing sintering with a transmittance of 65%.Studied the sintering time,sintering temperature,heating rate and pressure how to effect the materials'structure,morphology and optical properties.The best technological parameters for this experiment is that:in 900-1220?temperature range,9?/min heating heating rate isused,from 1220?to final sintering temperature range,heating rate is 3?/min,sintering temperature of 1550?,and keep 2 h at this temperature,the best value of40 Mpa pressure.Transparent glass ceramics combine the advantages of ceramics at mechanical properties and excellent optical properties of glass,and the preparation process is simple.Therefore,this paper also studies the preparation of magnesium-aluminum spinel transparent glass ceramics In this research,MgAl₂O₄ transparent glass ceramics is prepared by melt method using MgO-Al₂O₃-SiO₂?MAS?as a glass matrix,doped with Y₂O₃ and La₂O₃.The thermal properties of the glass system is analyzed,and the basic glass composition and heat treatment system are determined.The effects of Y₂O₃ and La₂O₃ doping and co-doping on the structure,morphology and optical properties of the samples are investigated.According to the experimental results,the heat treatment system of glass ceramics is determined as follows:at 800?soaking 4h,afterwards at 900?soaking 1.5 h;the optimal doping amount of oxide was 0.5mol%Y₂O₃,0.2 mol%La₂O₃,0.5 mol%Y₂O₃ and 0.5 mol%La₂O₃ co-doping;the relative content of spinel is 40.2%when 0.5 mol%Y₂O₃ and 0.5 mol%La₂O₃ are simultaneously doped,and the transmittance in the wavelength range of 400-2000 nm is more than 80%,sample crystal grains is a nearly spherical shape and distribute more uniform.