substitutes tion, high loosely dis Neodymium doped-yttrium aluminum garnet （Nd ： YAG） transparent polycrystalline ceramics already become of single crystals because they are provided with easy fabrication, low cost...substitutes tion, high loosely dis Neodymium doped-yttrium aluminum garnet （Nd ： YAG） transparent polycrystalline ceramics already become of single crystals because they are provided with easy fabrication, low cost, large size, highly doped concentraheat conductivity, mass fabrication, multi-layers and multi-filnctions. The Nd：YAG precursor powders with persed , slightly agglomerated, super fine and YAG cubic crystal phase were synthesized at 1100 ℃ by the homogeneous precipitation method, using Nd2O3, Y2O3, Al（NO3）3·9H2O and urea as raw materials, （NH4）2SO4 as electrical stabilizer, TEOS as sintering additive. The Nd：YAG transparent ceramics were prepared after being vacuum sintered at 1700 ℃ for 5 h. The Nd：YAG ceramic materials were characterized by the TG-DTA, XRD, FT-IR, TEM, FEG-ESEM and FT-PL. The results show that the crystallization temperature of YAG is 850 ℃ and the intermediate crystal phase YAP forming during the heat treatment transforms to YAG cubic crystal phase at 1050 ℃. The lasing wavelength of （Nd0.01 Y0.99）3Al5O12 transparent ceramics is 1.065 μm and there exists a slight red-shift compared to the single crystal with the same chemical composition. The optical transmittance is 45 % in the visible light and 58 % in the near infrared light and the optical transmittance descends with the decreasing the wavelength.展开更多
Nd ： YAG precursor powders were synthesized by homogeneous precipitation, and Nd ： YAG transparent ceramics were prepared by vacuum sintering at 1700 ℃ for 5 h. The ceramic materials were characterized by light tra...Nd ： YAG precursor powders were synthesized by homogeneous precipitation, and Nd ： YAG transparent ceramics were prepared by vacuum sintering at 1700 ℃ for 5 h. The ceramic materials were characterized by light transmittance and field emission gun-environment scanning microscope. Using statistics and stereology theory, study was carried out on the quantitative relationships between light transmittance and stereological parameters in three-dimensional Euclidean space. It is found that the transmittance of Nd：YAG with 1 mm in thickness is about 45% and 58% in visible and near-infrared wavelength, respectively. The transmittance linearly increases with increasing equivalent sphere diameter and reaches the theoretical value of single crystal when the equivalent sphere diameter is 20μm. The transmittance decreases with the increasing of mean specific area per unit volume of grain and discrete grains, and the transmittance decreases with increasing mean free distance of grains in Nd：YAG ceramics.展开更多
Transparent polycrystaUine neodymiumdoped yttrium aluminum garnet ceramics （Nd：YAG） with better chemical stability, excellent optical and high temperature mechanical property is becoming a new laser host material. ...Transparent polycrystaUine neodymiumdoped yttrium aluminum garnet ceramics （Nd：YAG） with better chemical stability, excellent optical and high temperature mechanical property is becoming a new laser host material. The Nd：YAG precursor powders with loosely dispersed, slightly agglomerated and YAG cubic crystal phase were synthesized at 1100 ℃ by the co-precipitation method combined with the reverse strike,展开更多
Nd∶YAG precursor powders were synthesized by homogeneous precipitation and Nd∶YAG transparent ceramics were prepared by vacuum sintering at 1700 ℃ for 5 h. The ceramic materials were characterized by light transmit...Nd∶YAG precursor powders were synthesized by homogeneous precipitation and Nd∶YAG transparent ceramics were prepared by vacuum sintering at 1700 ℃ for 5 h. The ceramic materials were characterized by light transmittance, field emission gun-environment scanning microscope. Fractal geometry was used to study the quantitative relationships between light transmittance and fractal dimensions of Nd∶YAG transparent ceramics. It was found that the transmittance of Nd∶YAG with 1 mm in thickness was about 45% and 58% in visible and near-infrared region respectively. The microstructures of Nd∶YAG transparent ceramics were obvious fractal characteristic and fractal dimensions depart a little from two-dimension. The light transmittance decreased with increasing of fractal dimension and nonlinear fit curve was y=1350-1185x+269x2 between fractal dimension and light transmittance of Nd∶YAG transparent ceramics.展开更多
The homogeneously dispersed, less agglomerated (Nd0.01Y0.99)3Al5O12 nano-sized powders were synthesized by the low temperature combustion (LCS), using Nd2O3, Y2O3, Al(NO3)3·9H2O, ammonia water and citric acid as ...The homogeneously dispersed, less agglomerated (Nd0.01Y0.99)3Al5O12 nano-sized powders were synthesized by the low temperature combustion (LCS), using Nd2O3, Y2O3, Al(NO3)3·9H2O, ammonia water and citric acid as starting materials. This method effectively solves the problems caused by solid-state reaction at high temperature and hard agglomerates brought by the chemical precipitation method. The powders were characterized by TG-DTA, XRD, FT-IR, TEM respectively and the photoluminescence (PL) spectra of (Nd0.01Y0.99)3Al5O12 green and sintered ceramic disks were measured. The results show that the forming temperature of YAG crystal phase is 850 ℃ and YAP crystal phase appearing during the calcinations transforms to pure YAG at 1050 ℃. The particle size of the powders synthesized by the LCS is in a range of 20～50 nm depending on the thermal treatment temperatures. The effectively induced cross section (σin) with the value 4.03×10-19 cm2 of (Nd0.01Y0.99)3Al5O12 ceramics is about 44% higher than that of single crystal.展开更多
Tetraethylenepentamine(C8H23N5,TEPA) has been used as a novel precipitant to synthesize yttrium aluminum garnet(Y3Al5O12,YAG) precursor from a mixed solution of aluminum and yttrium nitrates via a normal-strike co-pre...Tetraethylenepentamine(C8H23N5,TEPA) has been used as a novel precipitant to synthesize yttrium aluminum garnet(Y3Al5O12,YAG) precursor from a mixed solution of aluminum and yttrium nitrates via a normal-strike co-precipitation method without controlling the pH value during precipitation process.The original precursor was analyzed by thermogravimetry/differential scanning calorimetry(TG/DSC).The evolution of phase composition and micro-structure of the as-synthesized YAG powders were characterized by X-ray ...展开更多
（Nd0.01Y0.99）3Al5O12 nano-sized powders were synthesized by low temperature combustion （LCS）, using Nd2O3, Y2O3, Al（NO3）3.9H2O, ammonia water and citric acid as starting materials. The powders were characterized...（Nd0.01Y0.99）3Al5O12 nano-sized powders were synthesized by low temperature combustion （LCS）, using Nd2O3, Y2O3, Al（NO3）3.9H2O, ammonia water and citric acid as starting materials. The powders were characterized by TG-DTA, XRD, FT-IR, ICP and TEM, respectively. The grain sizes were calculated by the Scherrer＇s formula using the full width at half maximum （FWHM） of YAG （420） crystal plane diffraction lines. The study focused on crystallization of ceramics at different heat treatment temperatures. The experimental results show that crystallizing temperature of YAG is 850 ℃, and the intermediate crystal phase YAP, appearing during heat treatment, transforms to YAG cubic crystal phase at the temperature of 1 050℃. The particle size of the powders synthesized by LCS is nano-sized. With the temperature increasing, the mean grain sizes raise, the stand deviations keep almost at the value of 2.0 and the lattice parameters decrease. The grains mainly grow by grain boundary diffusion. The lattice parameter expansion is caused by an increase of the repulsive dipolar interactions on surfaces of crystallites,展开更多
Oxide melt growth ceramics(OMGCs)exhibit excellent performance and microstructure stability near their melt-ing point and are expected to become a new structural material for long-term stable service in extremely high...Oxide melt growth ceramics(OMGCs)exhibit excellent performance and microstructure stability near their melt-ing point and are expected to become a new structural material for long-term stable service in extremely high-temperature water-oxygen environments.Owing to its unique advantages of high efficiency,flexible manufac-turing,and near-net shaping,laser directed energy deposition(LDED)has become a promising technology for the rapid preparation of high-performance OMGCs.However,owing to the limited understanding of the crack-ing mechanism,the severe cracking problem that hinders OMGCs-LDED towards engineering applications has not been resolved.Alumina/aluminum titanate(Al_(2)O_(3)/Al_(x)Ti_(y)O_(z),A/AT)ceramics are prepared using an LDED system and their cracking characteristics are investigated.Subsequently,numerical simulations are conducted to reveal the dominant factors and influencing mechanisms of the cracking behavior.The results demonstrate that the cracking nucleation process is mainly controlled by solidification defects,whereas the cracking propagation process is determined primarily by both the microstructure and stress level.This study provides a theoretical basis for the development of appropriate cracking suppression methods for OMGCs-LDED.展开更多
Pe rsistent luminescence(Pers L)materials are widely used in safety indication,traffic and transportation signs,architectural decoration and other fields.In this paper,(Y_(1-x)Ce_(x))(Al_(0.9995)Cr_(0.0005))_(2)Ga_(3)...Pe rsistent luminescence(Pers L)materials are widely used in safety indication,traffic and transportation signs,architectural decoration and other fields.In this paper,(Y_(1-x)Ce_(x))(Al_(0.9995)Cr_(0.0005))_(2)Ga_(3)O_(12)(x=0.001,0.002,0.003,0.005)transparent ceramics were successfully prepared by solid-state reaction method in air followed by HIP post-treatment.With the increase of Cedoping concentration,the optical quality of the as-prepared ceramics is improved and the morphology is denser.Luminescent quenching occurs when the Ceconcentration is more than 0.2%.The as-prepared transparent ceramics we re annealed in different atmosphere s.From the PersL decay curve s,the transparent ce ramics after air annealing show the best PersL performance:luminance with 4424.0 mcd/m^(2)and PersL duration over865 min after ceasing 365 nm excitation,respectively.The effects of Cedoping concentration and annealing atmospheres are also discussed in detail.展开更多
Ultrafine-grained Al_(2)O_(3)–rare earth:yttrium aluminium garnet(Al_(2)O_(3)–RE:YAG)(RE=Ce;Ce+Gd)composite ceramics were obtained for the first time by reactive spark plasma sintering(SPS)using commercially availab...Ultrafine-grained Al_(2)O_(3)–rare earth:yttrium aluminium garnet(Al_(2)O_(3)–RE:YAG)(RE=Ce;Ce+Gd)composite ceramics were obtained for the first time by reactive spark plasma sintering(SPS)using commercially available initial oxide powders.The effect of key sintering parameters(temperature,dwell time,and external pressure(P_(load)))on densification peculiarities,structural-phase states,and luminescent properties of composites was studied comprehensively.Differences in phase formation and densification between Ce-doped and Ce,Gd-codoped systems were shown.Parameters of reactive SPS,at which there is partial melting with the formation of near-eutectic zones of the Al_(2)O_(3)–YAG system/coexistence of several variations of the YAG-type phase,were established.Pure corundum–garnet biphasic ceramics with an optimal balance between microstructural and luminescence performance were synthesized at 1425℃/30 min/30–60 MPa.The external quantum efficiency(EQE)of the phosphor converters reached 80.7%and 72%with close lifetime of~63.8 ns,similar to those of commercial Ce:YAG materials,which is promising for further applications in the field of high-power white light-emitting diodes(WLEDs)and laser diodes(LDs).展开更多
Silicon carbide (SiC) ceramic with YAG (Y3Al5O12) additive added by sol-gel method was liquid-phase sintered at different sintering temperatures, and the sintering mechanism and microstructural characteristics of resu...Silicon carbide (SiC) ceramic with YAG (Y3Al5O12) additive added by sol-gel method was liquid-phase sintered at different sintering temperatures, and the sintering mechanism and microstructural characteristics of resulting silicon carbide ceramics were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and elemental distribution of surface (EDS). YAG (yttrium aluminum garnet) phase formed before the sintering and its uniform distribution in the SiC/YAG composite powder decreased the sintering temperature and improved the densification of SiC ceramic. The suitable sintering temperature was 1860 °C with the specimen sintered at this temperature having superior sintering and mechanical properties, smaller crystal size and fewer microstructure defects. Three characteristics of improved toughness of SiC ceramic with YAG added by sol-gel method were microstructural densification, main-crack deflection and crystal ‘bridging’.展开更多
A neodymium doped yttrium aluminum gamet （Nd：YAG） transparent ceramic was fabricated by a solid state reaction method using commercial α-Al2O3, Y2O3, and Nd2O3 powders as starting materials and tetraethyl orthosil...A neodymium doped yttrium aluminum gamet （Nd：YAG） transparent ceramic was fabricated by a solid state reaction method using commercial α-Al2O3, Y2O3, and Nd2O3 powders as starting materials and tetraethyl orthosilicate （TEOS） as sintefing aid. The morphology and microstructure of the nanopowders and the Nd：YAG transparent ceramic were investigated. The fully dense Nd：YAG ceramic with an average grain size of-20 μm was obtained by vacuum sintering at 1720℃ for 12 h. Few pores and grain-boundary phases were observed. The in-line transmittance of the ceramic was 81.5% at 1064 nm.展开更多
Nd/Yb-co-doped YAG transparent ceramic nano-powder was prepared by a sol-gel combustion method.The structure,morphology and properties were characterized by thermogravimetric-differential thermal analysis,X-ray diffra...Nd/Yb-co-doped YAG transparent ceramic nano-powder was prepared by a sol-gel combustion method.The structure,morphology and properties were characterized by thermogravimetric-differential thermal analysis,X-ray diffraction,transmission electron microscopy,infrared spectroscopy,absorption analysis and fluorescence spectroscopy,respectively.The results show that the mass loss of the powder calcinated at 900 ℃ for 3 h is 49.56%.A well-crystallized Nd/Yb:YAG nano-powder with the superior sintering performance and high purity is obtained,and the morphology of the particles with the average diameter in the range of 60-100 runs appears regular.The nano-powder exhibits an intense absorption at 808 nm,corresponding to the 4I/9/2-4F7/2 transition of Nd^(^(3+) ions,which is suitable to absorb the wavelength of 808 nm from a laser diode source.The emission peak at 1046 nm of the Nd/Yb:YAG powder is more intense than that of Nd^(^(3+):YAG powder.It is indicated that the energy absorbed by Yb^(^(3+) ions from the laser diode source can be transmitted to Nd^(^(3+) ions based on the cross relaxation process of[(4F3/2)Nd,(2F7/2)Yb]-[(479/2)Nd,(2F5/2)Yb].展开更多
文摘substitutes tion, high loosely dis Neodymium doped-yttrium aluminum garnet （Nd ： YAG） transparent polycrystalline ceramics already become of single crystals because they are provided with easy fabrication, low cost, large size, highly doped concentraheat conductivity, mass fabrication, multi-layers and multi-filnctions. The Nd：YAG precursor powders with persed , slightly agglomerated, super fine and YAG cubic crystal phase were synthesized at 1100 ℃ by the homogeneous precipitation method, using Nd2O3, Y2O3, Al（NO3）3·9H2O and urea as raw materials, （NH4）2SO4 as electrical stabilizer, TEOS as sintering additive. The Nd：YAG transparent ceramics were prepared after being vacuum sintered at 1700 ℃ for 5 h. The Nd：YAG ceramic materials were characterized by the TG-DTA, XRD, FT-IR, TEM, FEG-ESEM and FT-PL. The results show that the crystallization temperature of YAG is 850 ℃ and the intermediate crystal phase YAP forming during the heat treatment transforms to YAG cubic crystal phase at 1050 ℃. The lasing wavelength of （Nd0.01 Y0.99）3Al5O12 transparent ceramics is 1.065 μm and there exists a slight red-shift compared to the single crystal with the same chemical composition. The optical transmittance is 45 % in the visible light and 58 % in the near infrared light and the optical transmittance descends with the decreasing the wavelength.
基金Project supported by Key Science and Technology of Chinese Ministry of Education (205037)
文摘Nd ： YAG precursor powders were synthesized by homogeneous precipitation, and Nd ： YAG transparent ceramics were prepared by vacuum sintering at 1700 ℃ for 5 h. The ceramic materials were characterized by light transmittance and field emission gun-environment scanning microscope. Using statistics and stereology theory, study was carried out on the quantitative relationships between light transmittance and stereological parameters in three-dimensional Euclidean space. It is found that the transmittance of Nd：YAG with 1 mm in thickness is about 45% and 58% in visible and near-infrared wavelength, respectively. The transmittance linearly increases with increasing equivalent sphere diameter and reaches the theoretical value of single crystal when the equivalent sphere diameter is 20μm. The transmittance decreases with the increasing of mean specific area per unit volume of grain and discrete grains, and the transmittance decreases with increasing mean free distance of grains in Nd：YAG ceramics.
文摘Transparent polycrystaUine neodymiumdoped yttrium aluminum garnet ceramics （Nd：YAG） with better chemical stability, excellent optical and high temperature mechanical property is becoming a new laser host material. The Nd：YAG precursor powders with loosely dispersed, slightly agglomerated and YAG cubic crystal phase were synthesized at 1100 ℃ by the co-precipitation method combined with the reverse strike,
基金Study on Optical Properties and Structure of Transparent Ceramics,Chinese Education Ministry Excellent Teachers Project (KB200226)
文摘Nd∶YAG precursor powders were synthesized by homogeneous precipitation and Nd∶YAG transparent ceramics were prepared by vacuum sintering at 1700 ℃ for 5 h. The ceramic materials were characterized by light transmittance, field emission gun-environment scanning microscope. Fractal geometry was used to study the quantitative relationships between light transmittance and fractal dimensions of Nd∶YAG transparent ceramics. It was found that the transmittance of Nd∶YAG with 1 mm in thickness was about 45% and 58% in visible and near-infrared region respectively. The microstructures of Nd∶YAG transparent ceramics were obvious fractal characteristic and fractal dimensions depart a little from two-dimension. The light transmittance decreased with increasing of fractal dimension and nonlinear fit curve was y=1350-1185x+269x2 between fractal dimension and light transmittance of Nd∶YAG transparent ceramics.
文摘The homogeneously dispersed, less agglomerated (Nd0.01Y0.99)3Al5O12 nano-sized powders were synthesized by the low temperature combustion (LCS), using Nd2O3, Y2O3, Al(NO3)3·9H2O, ammonia water and citric acid as starting materials. This method effectively solves the problems caused by solid-state reaction at high temperature and hard agglomerates brought by the chemical precipitation method. The powders were characterized by TG-DTA, XRD, FT-IR, TEM respectively and the photoluminescence (PL) spectra of (Nd0.01Y0.99)3Al5O12 green and sintered ceramic disks were measured. The results show that the forming temperature of YAG crystal phase is 850 ℃ and YAP crystal phase appearing during the calcinations transforms to pure YAG at 1050 ℃. The particle size of the powders synthesized by the LCS is in a range of 20～50 nm depending on the thermal treatment temperatures. The effectively induced cross section (σin) with the value 4.03×10-19 cm2 of (Nd0.01Y0.99)3Al5O12 ceramics is about 44% higher than that of single crystal.
文摘Tetraethylenepentamine(C8H23N5,TEPA) has been used as a novel precipitant to synthesize yttrium aluminum garnet(Y3Al5O12,YAG) precursor from a mixed solution of aluminum and yttrium nitrates via a normal-strike co-precipitation method without controlling the pH value during precipitation process.The original precursor was analyzed by thermogravimetry/differential scanning calorimetry(TG/DSC).The evolution of phase composition and micro-structure of the as-synthesized YAG powders were characterized by X-ray ...
基金the Chinese Education Ministry Excellent Teacher Foundation(KB20026)
文摘（Nd0.01Y0.99）3Al5O12 nano-sized powders were synthesized by low temperature combustion （LCS）, using Nd2O3, Y2O3, Al（NO3）3.9H2O, ammonia water and citric acid as starting materials. The powders were characterized by TG-DTA, XRD, FT-IR, ICP and TEM, respectively. The grain sizes were calculated by the Scherrer＇s formula using the full width at half maximum （FWHM） of YAG （420） crystal plane diffraction lines. The study focused on crystallization of ceramics at different heat treatment temperatures. The experimental results show that crystallizing temperature of YAG is 850 ℃, and the intermediate crystal phase YAP, appearing during heat treatment, transforms to YAG cubic crystal phase at the temperature of 1 050℃. The particle size of the powders synthesized by LCS is nano-sized. With the temperature increasing, the mean grain sizes raise, the stand deviations keep almost at the value of 2.0 and the lattice parameters decrease. The grains mainly grow by grain boundary diffusion. The lattice parameter expansion is caused by an increase of the repulsive dipolar interactions on surfaces of crystallites,
基金supported by National Natural Science Founda-tion of China(Grant.Nos.51805070,51790172,52175291)Funda-mental Research Funds for the Central Universities of China(Grant.Nos.DUT22YG210,DUT22LAB117)+1 种基金Science Center for Gas Turbine Project of China(Grant.No.P2022-B-IV-012-001)Shenzhen Sci-ence and Technology Innovation Commission of China(Grant.No.JCYJ20210324115413036).
文摘Oxide melt growth ceramics(OMGCs)exhibit excellent performance and microstructure stability near their melt-ing point and are expected to become a new structural material for long-term stable service in extremely high-temperature water-oxygen environments.Owing to its unique advantages of high efficiency,flexible manufac-turing,and near-net shaping,laser directed energy deposition(LDED)has become a promising technology for the rapid preparation of high-performance OMGCs.However,owing to the limited understanding of the crack-ing mechanism,the severe cracking problem that hinders OMGCs-LDED towards engineering applications has not been resolved.Alumina/aluminum titanate(Al_(2)O_(3)/Al_(x)Ti_(y)O_(z),A/AT)ceramics are prepared using an LDED system and their cracking characteristics are investigated.Subsequently,numerical simulations are conducted to reveal the dominant factors and influencing mechanisms of the cracking behavior.The results demonstrate that the cracking nucleation process is mainly controlled by solidification defects,whereas the cracking propagation process is determined primarily by both the microstructure and stress level.This study provides a theoretical basis for the development of appropriate cracking suppression methods for OMGCs-LDED.
基金Project supported by the National Key R&D Program of China(2021YFE0104800)Joint Funds of the National Natural Science Foundation of China(U1932160)National Center for Research and Development(WPC2/1/SCAPOL/2021)。
文摘Pe rsistent luminescence(Pers L)materials are widely used in safety indication,traffic and transportation signs,architectural decoration and other fields.In this paper,(Y_(1-x)Ce_(x))(Al_(0.9995)Cr_(0.0005))_(2)Ga_(3)O_(12)(x=0.001,0.002,0.003,0.005)transparent ceramics were successfully prepared by solid-state reaction method in air followed by HIP post-treatment.With the increase of Cedoping concentration,the optical quality of the as-prepared ceramics is improved and the morphology is denser.Luminescent quenching occurs when the Ceconcentration is more than 0.2%.The as-prepared transparent ceramics we re annealed in different atmosphere s.From the PersL decay curve s,the transparent ce ramics after air annealing show the best PersL performance:luminance with 4424.0 mcd/m^(2)and PersL duration over865 min after ceasing 365 nm excitation,respectively.The effects of Cedoping concentration and annealing atmospheres are also discussed in detail.
基金supported by the Russian Science Foundation(No.20-73-10242)Also,this work was partially supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA22010301)+3 种基金the International Partnership Program of Chinese Academy of Sciences(No.121631KYSB20200039)the International Cooperation Project of Shanghai Science and Technology Commission(No.20520750200)Denis Yu.Kosyanov is grateful to the Council on grants of the President of the Russian Federation(No.SP-3221.2022.1)for supporting the studies devoted to obtaining advanced ceramic materialsThe SR XRD measurements were done at the shared research center SSTRC on the basis of the VEPP-4-VEPP-2000 complex at the Budker Institute of Nuclear Physics SB RAS.
文摘Ultrafine-grained Al_(2)O_(3)–rare earth:yttrium aluminium garnet(Al_(2)O_(3)–RE:YAG)(RE=Ce;Ce+Gd)composite ceramics were obtained for the first time by reactive spark plasma sintering(SPS)using commercially available initial oxide powders.The effect of key sintering parameters(temperature,dwell time,and external pressure(P_(load)))on densification peculiarities,structural-phase states,and luminescent properties of composites was studied comprehensively.Differences in phase formation and densification between Ce-doped and Ce,Gd-codoped systems were shown.Parameters of reactive SPS,at which there is partial melting with the formation of near-eutectic zones of the Al_(2)O_(3)–YAG system/coexistence of several variations of the YAG-type phase,were established.Pure corundum–garnet biphasic ceramics with an optimal balance between microstructural and luminescence performance were synthesized at 1425℃/30 min/30–60 MPa.The external quantum efficiency(EQE)of the phosphor converters reached 80.7%and 72%with close lifetime of~63.8 ns,similar to those of commercial Ce:YAG materials,which is promising for further applications in the field of high-power white light-emitting diodes(WLEDs)and laser diodes(LDs).
基金Project (No. 2004C31044) supported by the Science & TechniqueProject of Zhejiang Province, China
文摘Silicon carbide (SiC) ceramic with YAG (Y3Al5O12) additive added by sol-gel method was liquid-phase sintered at different sintering temperatures, and the sintering mechanism and microstructural characteristics of resulting silicon carbide ceramics were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and elemental distribution of surface (EDS). YAG (yttrium aluminum garnet) phase formed before the sintering and its uniform distribution in the SiC/YAG composite powder decreased the sintering temperature and improved the densification of SiC ceramic. The suitable sintering temperature was 1860 °C with the specimen sintered at this temperature having superior sintering and mechanical properties, smaller crystal size and fewer microstructure defects. Three characteristics of improved toughness of SiC ceramic with YAG added by sol-gel method were microstructural densification, main-crack deflection and crystal ‘bridging’.
基金supported by the Natural Science fund of Jiangsu Province,China(No.BK2007724)
文摘A neodymium doped yttrium aluminum gamet （Nd：YAG） transparent ceramic was fabricated by a solid state reaction method using commercial α-Al2O3, Y2O3, and Nd2O3 powders as starting materials and tetraethyl orthosilicate （TEOS） as sintefing aid. The morphology and microstructure of the nanopowders and the Nd：YAG transparent ceramic were investigated. The fully dense Nd：YAG ceramic with an average grain size of-20 μm was obtained by vacuum sintering at 1720℃ for 12 h. Few pores and grain-boundary phases were observed. The in-line transmittance of the ceramic was 81.5% at 1064 nm.
基金supported by special project of Changchun Science & Technology Office(2014228)the Development and Reform Commission of Jilin Province(2015Y69)
文摘Nd/Yb-co-doped YAG transparent ceramic nano-powder was prepared by a sol-gel combustion method.The structure,morphology and properties were characterized by thermogravimetric-differential thermal analysis,X-ray diffraction,transmission electron microscopy,infrared spectroscopy,absorption analysis and fluorescence spectroscopy,respectively.The results show that the mass loss of the powder calcinated at 900 ℃ for 3 h is 49.56%.A well-crystallized Nd/Yb:YAG nano-powder with the superior sintering performance and high purity is obtained,and the morphology of the particles with the average diameter in the range of 60-100 runs appears regular.The nano-powder exhibits an intense absorption at 808 nm,corresponding to the 4I/9/2-4F7/2 transition of Nd^(^(3+) ions,which is suitable to absorb the wavelength of 808 nm from a laser diode source.The emission peak at 1046 nm of the Nd/Yb:YAG powder is more intense than that of Nd^(^(3+):YAG powder.It is indicated that the energy absorbed by Yb^(^(3+) ions from the laser diode source can be transmitted to Nd^(^(3+) ions based on the cross relaxation process of[(4F3/2)Nd,(2F7/2)Yb]-[(479/2)Nd,(2F5/2)Yb].
