大尺寸La_2O_3-TiO_2-ZrO_2非晶塑性烧结行为
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摘要
La_2O_3-TiO_2-ZrO_2玻璃具有很高的折射率,在镜头材料和上转换发光基质材料等领域表现出良好的应用前景,但其玻璃形成能力低,通常只能采用快速冷却的方法制备,因此难以获得大尺寸材料。为了获得大尺寸La_2O_3-TiO_2-ZrO_2玻璃,本研究采用La_2O_3-TiO_2-ZrO_2非晶粉末为原料,利用非晶在玻璃转变温度以上的塑性行为,在温度动力学窗口ΔT内进行热压烧结制备了大尺寸La_2O_3-TiO_2-ZrO_2玻璃,在保持非晶的前提下实现了La_2O_3-TiO_2-ZrO_2粉末的完全致密化。采用SEM、XRD等方法研究了样品的显微结构和相组成。研究发现,当烧结温度高于910℃时,烧结过程中会析出La4Ti9O24晶相;当烧结温度低于900℃时,样品保持良好的非晶性,并随着烧结温度的增加,样品的致密度有所升高。烧结压力也会影响烧结过程,样品的致密度随着烧结压力升高而增加。大尺寸La_2O_3-TiO_2-ZrO_2非晶材料具有很高的折射率,在587.6nm处折射率可达到2.33。在La_2O_3-TiO_2-ZrO_2非晶粉末烧结过程中,塑性流动是其主要的传质机理。
La_2O_3-TiO_2-ZrO_2 glass has great potential applications in lens and upconversion host materials for its ultrahigh refractive index. However, due to its low glass forming ability, it can only be prepared by some extremely rapid melt cooling method, which is hard to produce large-sized materials. On the basis of amorphous plastic behavior above the glass transition temperature Tg, large-sized La_2O_3-TiO_2-ZrO_2 bulk glasses were obtained by hot pressed sintering within the thermodynamic window ΔT. 30.8% LaO3/2-59.2% TiO2-10% ZrO2 amorphous spheres were firstly prepared by aerodynamic levitation furnace. Whereafter, these spheres were smashed and ground into powders. Then these glass powders were hot pressed into a bulk glass with dimension of f20 mm×1 mm. The effects of sintering temperature and pressure on the process of hot pressed sintering were investigated. Microstructures and phase compositions of samples were studied by SEM and XRD. The results show that the samples sintered above 910 ℃ contain a few La4 Ti9 O24 crystal phases, while the samples sintered below 900 ℃ are totally amorphous. When the sintering temperature is below 900 ℃, the increase of sintering temperature in a certain range can reduce the number of pores apparently to improve the density of samples. And with the increase of pressure from 20 MPa to 60 MPa, the density of bulk glass prepared by hot pressing at 900 ℃ increases from 4.8797 g/cm3 to 5.1178 g/cm3. The large-sized La_2O_3-TiO_2-ZrO_2 glass displays excellent optical performance with refractive index of 2.33 at the wavelength of 587.6 nm and the abbe number of 13.2. By analyzing the shrinkage curve of the samples, it is confirmed that the plastic flow is the main mass transfer way during densification process.
La_2O_3-TiO_2-ZrO_2 glass has great potential applications in lens and upconversion host materials for its ultrahigh refractive index. However, due to its low glass forming ability, it can only be prepared by some extremely rapid melt cooling method, which is hard to produce large-sized materials. On the basis of amorphous plastic behavior above the glass transition temperature Tg, large-sized La_2O_3-TiO_2-ZrO_2 bulk glasses were obtained by hot pressed sintering within the thermodynamic window ΔT. 30.8% LaO3/2-59.2% TiO2-10% ZrO2 amorphous spheres were firstly prepared by aerodynamic levitation furnace. Whereafter, these spheres were smashed and ground into powders. Then these glass powders were hot pressed into a bulk glass with dimension of f20 mm×1 mm. The effects of sintering temperature and pressure on the process of hot pressed sintering were investigated. Microstructures and phase compositions of samples were studied by SEM and XRD. The results show that the samples sintered above 910 ℃ contain a few La4 Ti9 O24 crystal phases, while the samples sintered below 900 ℃ are totally amorphous. When the sintering temperature is below 900 ℃, the increase of sintering temperature in a certain range can reduce the number of pores apparently to improve the density of samples. And with the increase of pressure from 20 MPa to 60 MPa, the density of bulk glass prepared by hot pressing at 900 ℃ increases from 4.8797 g/cm3 to 5.1178 g/cm3. The large-sized La_2O_3-TiO_2-ZrO_2 glass displays excellent optical performance with refractive index of 2.33 at the wavelength of 587.6 nm and the abbe number of 13.2. By analyzing the shrinkage curve of the samples, it is confirmed that the plastic flow is the main mass transfer way during densification process.
引文
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[2]YODA S,CHO W S,IMAI R.Aerodynamic levitator for largesized glassy material production.Review of Scientific Instruments,2015,86(9):21-27.
[3]XIANG H,GUAN L,PENG Z,et al.Preparation of high refractive index La2O3-Ti O2 glass by aerodynamic levitation technique and effects of Bi2O3,substitution on its thermal and optical properties.Ceramics International,2014,40(3):4985-4988.
[4]ZHANG M,WEN H,YU H,et al.Study on upconversion luminescence and thermal properties of Ho3+/Yb3+co-doped La2O3-Ti O2-Zr O2 glasses.Journal of Alloys&Compounds,2016,672(5):7-12.
[5]WANG C,AI F,WEN H,et al.Effect of Yb3+on the upconversion luminescence of Tm3+/Yb3+co-doped La2O3-Ti O2-Zr O2 glasses.Optical Materials Express,2015,5(4):676-683.
[6]INOUE H,WATANABE Y,MASUNO A,et al.Effect of substituting Al2O3 and Zr O2 on thermal and optical properties of high refractive index La2O3-Ti O2 glass system prepared by containerless processing.Optical Materials,2011,33(12):1853-1857.
[7]KANEKO M,KENTEI YU Y,KUMAR V,et al.Glass Forming in La2O3-Ti O2-Zr O2 Ternary System by Containerless Processing.38th COSPAR Scientific Assembly.Bremen,2010:8-12.
[8]ZHU MEI-JUAN,YU JIAN-DING,ZHANG MING-HUI,et al.Upconversion luminescence of Er3+/Yb3+co-doped La2O3-Ti O2-Zr O2 glasses prepared by containerless processing.Journal of Inorganic Materials,2015,30(4):391-396.
[9]PAN X,YU J,LIU Y,et al.Infrared to visible upconversion luminescence in Er3+/Yb3+doped titanate glass prepared by containerless processing.Journal of Luminescence,2012,132(4):1025-1029.
[10]ZHANG M,YU J,PAN X,et al.Increase of the blue upconversion emission in Tm3+/Yb3+,co-doped titanate glass ceramics.Journal of Non-Crystalline Solids,2013,378(11):106-109.
[11]ROSENFLANZ A,FREY M,ENDRES B,et al.Bulk glasses and ultrahard nanoceramics based on alumina and rare-earth oxides.Nature,2004,430(7001):761-764.
[12]WANG L,MEI L,HE G,et al.Preparation of Ce:YAG glassceramics with low Si O2.Journal of the American Ceramic Society,2011,94(11):3800-3803.
[13]MEI L,HE G,WANG L L,et al.Fabrication of transparent La Al O3/t-Zr O2,nanoceramics through controlled amorphous crystallization.Journal of the European Ceramic Society,2011,31(9):1603-1609.
[14]WANG L L,MEI L,HE G,et al.Preparation of infrared transparent YAG-based glass-ceramics with nano-sized crystallites.Journal of the European Ceramic Society,2012,32(12):3091-3096.
[15]WANG L L,MEI L,LIU G H,et al.Optical and mechanical properties of amorphous bulk and eutectic ceramics in the Hf O2-Al2O3-Y2O3 system.Ceramics International,2013,39(1):233-238.
[16]MEI L,LIU G H,HE G,et al.Controlled amorphous crystallization:an easy way to make transparent nanoceramics.Optical Materials,2012,34(6):981-985.
[17]汪卫华.非晶态物质的本质和特性.物理学进展,2013,33(5):177-351.
[18]DIMITROV V,SAKKA S.Electronic oxide polarizability and optical basicity of simple oxides.Journal of Applied Physics,1996,79(3):1736-1740.
[19]MA X,PENG Z,LI J.Effect of Ta2O5 substituting on thermal and optical properties of high refractive index La2O3-Nb2O5 glass system prepared by aerodynamic levitation method.Journal of the American Ceramic Society,2015,98(3):770-773.
[20]SHI J L,LIN Z X.The flow characteristics of hot-pressing of beta-Al2O3.Ceramics International,1989,15(2):107-112.