Preparation And Study On Properties Of Transparent Alumina Ceramics

Alumina ceramics have a wide range of applications in the fields of mechanical,semiconductor,electronics,military,medical and other high-tech fields because of its high temperature resistance,corrosion resistance,excellent mechanical properties,good optical and mechanical properties and other physical and chemical properties.In this paper,translucent Al2O3 ceramics were prepared by vacuum sintering using Y3+,La3 + and Mg2+ as sintering aids which were introduced via chemical precipitation.The morphology,structure,optical and mechanical properties of the samples were tested by density test,X-ray diffraction?XRD?,energy dispersive spectroscopy?EDS?,scanning electron microscopy?SEM?,ultraviolet infrared spectrophotometer and indentation method,mainly analyzed the effects of the sintering aids on optical transmittance of the translucent Al2O3 ceramics.What is more,aluminum isopropoxide was used as raw material,a stable boehmite sol was prepared by sol-gel method,and the alumina ceramic film was prepared by spin coating method.The as-prepared samples were characterized by Fourier transform infrared spectroscopy?FT-IR?XRD,SEM and atomic microscope?AFM?,the influence factors of the stability of boehmite sol and the formation of film were also studied.The results show that sintering aids introduced by the chemical precipitation method can be uniformly distributed in the alumina ceramics without agglomeration and the second phase.The addition of Y3 + could promote grain growth and decrease porosity,thus the optical transmittance of the translucent Al2O3 ceramics is enhanced.The optimal amount of the sintering aid introduced is Mg2 +?0.15 wt.%?,Y3+?0.05 wt.%?and La3 +?0.05 wt.%?,and the corresponding sample shows the grain size is uniform,which is about 25-35 ?m,and no pores exist;the relative density is achieved 99.62%,and the highest total forward transmittance which is above 80% in the wavelength range of 350-800 nm.What is more,the effect of Y and Mg on the microstructure of the sample is different,therefore,the Vickers hardness of the sample increases with the increase of Y content,and Mg has little effect on the hardness of the sample.The boehmite sol is prepared by sol-gel method,when n?Al?C3H7O?3?: n?H2O?: n?HNO3?= 1: 100:0.3,a light blue transparent sol was prepared which exhibited the best stability;Optimizing the heat treatment process to prevent the film from falling off during the sintering process,the prepared film shows smooth surface,the root mean square roughness?RMS?was about 3.2 nm,and the ceramic film was ?-Al₂O₃ crystal phase.