Study On The Fabrication,Microstructure And Properties Of Tm₂O₃ Transparent Ceramics

Compared with glasses and single crystals,transparent ceramics,as a kind of optical material,have been widely applied in optical window,solid-laser and illumination fields because of more excellent mechanical,thermal,anti-corrosion and other properties.Tm₂O₃,one of the rare-earth sesquioxides,could obtain the unique optical function and possess good application value at the wave band of 1.4 and 2.0μm,which was attributed to its unique electron shell structure.At the same time,it has obvious advantage as a solid-laser material due to the excellent thermal properties.In this study,the highly transparent Tm₂O₃ ceramics were successfully fabricated at a relatively low vacuum sintering temperature by commercial powders.And the influence of sintering additives on the optical,thermal,mechanical properties,and the evolution of microstructure of Tm₂O₃ transparent ceramics were analyzed systematically.The research content of this study is as follows.The 1 at%Zr O₂:Tm₂O₃ powders were employed as the starting material and the vacuum sintering process was set at 1800℃for 8 hours to compare the results.The effects of the morphology of starting powders and annealing process of sintered compacts on the optical properties were studied.The in-line transmittance of 1 at%Zr O₂:Tm₂O₃ transparent ceramics reached 77.3%,75.4%and 77.2%at the wavelength of 880 nm,respectively,with the ball-milled time of 26 hours,the calcination temperature of 1000℃and the annealing temperature at 1200℃.The influence of vacuum sintering temperature and Zr O₂ doping concentration on the properties and microstructure of Tm₂O₃ transparent ceramics were studied.The in-line transmittance of 1 at%Zr O₂:Tm₂O₃ reached 75.0%at 880 nm and fluctuated around 80%from 2100 to 2400 nm when the vacuum sintering temperature was 1800 and 1850℃.In the sample series with different doping concentrations,the in-line transmittance of 3 at%Zr O₂:Tm₂O₃ improved to 76.3%at 880 nm,which achieved 94.2%of the theoretical value.The Vickers hardness and fracture toughness was 9.90±0.44 GPa and 1.25±0.10 MPa·m^1/2respectively.The thermal diffusivity and conductivity were 1.3 mm~2/s and 7.15 W/（m·K）,respectively.The effects of vacuum sintering temperature on the optical properties and microstructure of 1 at%Ti O₂:Tm₂O₃ and 1 at%Ti O₂,1 at%Zr O₂:Tm₂O₃ transparent ceramics were studied.The in-line transmittance both of them was reached highest value,66.0%and 71.3%at 880nm respectively,when the sintering temperature reached 1750℃.The in-line transmittance increased first and then decreased with the increasing of sintering temperature,which may be caused by the transformation of pores type.And the average grain size of 1 at%Ti O₂,1 at%Zr O₂:Tm₂O₃,11.27±0.12μm,was smaller than 1 at%Ti O₂:Tm₂O₃,19.86±1.25μm,at the sintering temperature of 1750℃.