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
The phosphor Y2O2S:Eu3+ powder crystal has been synthesized by using the microwave thermal method.The data of X-ray powder diffraction showed that the phosphor structure belongs to hexagonal system with lattice parame...The phosphor Y2O2S:Eu3+ powder crystal has been synthesized by using the microwave thermal method.The data of X-ray powder diffraction showed that the phosphor structure belongs to hexagonal system with lattice parameters a=0.3785 nm,c=0.6590nm.The excitation spectrum of the phosphor is a broad band with peak at λ(ex)= 261 nm.The main emission peak at λ(em)=626nm and the other emission lines peak at 595,617 and 706 nm are assigned to transitions of the Eu3+ respectively.Under 254 nm excitation,the chromatic coordinates of phosphor are x=0.665, y=0.330.The relative luminescent intensity is about 62% compared with the standard phosphor Y2O3:Eu3+.Under 365nm excitation this phosphor gives rise to an intense red light.The phosphor particle size has a medium diameter of 7.3μm.展开更多
This work was conducted to study the ability of anodic oxidation of azo dye C.I. Acid Red 73 （ART3） using the yttrium-doped Ti/SnO2-Sb electrodes. The effects of Sb doping level, yttrium doping level, thermal decomp...This work was conducted to study the ability of anodic oxidation of azo dye C.I. Acid Red 73 （ART3） using the yttrium-doped Ti/SnO2-Sb electrodes. The effects of Sb doping level, yttrium doping level, thermal decomposition temperature and cycle times of dip-coating thermal decomposition on the properties of the electrodes were investigated. The results showed that the excellent electrochemical activity of Ti/SnO2-Sb-Y electrode can be achieved at a 7：1 molar ratio of Sn：Sb and thermal decomposition temperature of 550~C. Moreover when the cycle times of dip-coating and thermal decomposition were up to 10 times, the performance of the electrode tends to be stable. The Ti/SnO2-Sb electrodes doped with yttrium （0.5 tool-%） showed the most excellent electrochemical activity. In addition, the influences of operating variables, including current density, initial pH, dye concentration and support electrolyte, on the colour removal, chemical oxygen demand （COD） removal and current efficiency were also investigated. Our results confirmed that the current efficiency increased with the concentrations of dye and sodium chloride. Moreover, increasing the current density and the initial pH would reduce the current efficiency.展开更多
By controlling the amorphous-to-crystalline relative volume,chalcogenide phase-change memory materials can provide multi-level data storage(MLS),which offers great potential for high-density storageclass memory and ne...By controlling the amorphous-to-crystalline relative volume,chalcogenide phase-change memory materials can provide multi-level data storage(MLS),which offers great potential for high-density storageclass memory and neuro-inspired computing.However,this type of MLS system suffers from high power consumption and a severe time-dependent resistance increase(‘‘drift")in the amorphous phase,which limits the number of attainable storage levels.Here,we report a new type of MLS system in yttriumdoped antimony telluride,utilizing reversible multi-level phase transitions between three states,i.e.,amorphous,metastable cubic and stable hexagonal crystalline phases,with ultralow power consumption(0.6–4.3 p J)and ultralow resistance drift for the lower two states(power-law exponent<0.007).The metastable cubic phase is stabilized by yttrium,while the evident reversible cubic-to-hexagonal transition is attributed to the sequential and directional migration of Sb atoms.Finally,the decreased heat dissipation of the material and the increase in crystallinity contribute to the overall high performance.This study opens a new way to achieve advanced multi-level phase-change memory without the need for complicated manufacturing procedures or iterative programming operations.展开更多
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The phosphor Y2O2S:Eu3+ powder crystal has been synthesized by using the microwave thermal method.The data of X-ray powder diffraction showed that the phosphor structure belongs to hexagonal system with lattice parameters a=0.3785 nm,c=0.6590nm.The excitation spectrum of the phosphor is a broad band with peak at λ(ex)= 261 nm.The main emission peak at λ(em)=626nm and the other emission lines peak at 595,617 and 706 nm are assigned to transitions of the Eu3+ respectively.Under 254 nm excitation,the chromatic coordinates of phosphor are x=0.665, y=0.330.The relative luminescent intensity is about 62% compared with the standard phosphor Y2O3:Eu3+.Under 365nm excitation this phosphor gives rise to an intense red light.The phosphor particle size has a medium diameter of 7.3μm.
基金The authors are grateful for the financial support from the National Natural Science Foundation of China （Grant No. 21276177）, and the Natural Science Foundation of Tianjin （Grant No. 10JCYBJC04900）.
文摘This work was conducted to study the ability of anodic oxidation of azo dye C.I. Acid Red 73 （ART3） using the yttrium-doped Ti/SnO2-Sb electrodes. The effects of Sb doping level, yttrium doping level, thermal decomposition temperature and cycle times of dip-coating thermal decomposition on the properties of the electrodes were investigated. The results showed that the excellent electrochemical activity of Ti/SnO2-Sb-Y electrode can be achieved at a 7：1 molar ratio of Sn：Sb and thermal decomposition temperature of 550~C. Moreover when the cycle times of dip-coating and thermal decomposition were up to 10 times, the performance of the electrode tends to be stable. The Ti/SnO2-Sb electrodes doped with yttrium （0.5 tool-%） showed the most excellent electrochemical activity. In addition, the influences of operating variables, including current density, initial pH, dye concentration and support electrolyte, on the colour removal, chemical oxygen demand （COD） removal and current efficiency were also investigated. Our results confirmed that the current efficiency increased with the concentrations of dye and sodium chloride. Moreover, increasing the current density and the initial pH would reduce the current efficiency.
基金the National Key Research and Development Program of China(2017YFB0701700)the National Natural Science Foundation of China(51872017)the High-Performance Computing(HPC)Resources at Beihang University。
文摘By controlling the amorphous-to-crystalline relative volume,chalcogenide phase-change memory materials can provide multi-level data storage(MLS),which offers great potential for high-density storageclass memory and neuro-inspired computing.However,this type of MLS system suffers from high power consumption and a severe time-dependent resistance increase(‘‘drift")in the amorphous phase,which limits the number of attainable storage levels.Here,we report a new type of MLS system in yttriumdoped antimony telluride,utilizing reversible multi-level phase transitions between three states,i.e.,amorphous,metastable cubic and stable hexagonal crystalline phases,with ultralow power consumption(0.6–4.3 p J)and ultralow resistance drift for the lower two states(power-law exponent<0.007).The metastable cubic phase is stabilized by yttrium,while the evident reversible cubic-to-hexagonal transition is attributed to the sequential and directional migration of Sb atoms.Finally,the decreased heat dissipation of the material and the increase in crystallinity contribute to the overall high performance.This study opens a new way to achieve advanced multi-level phase-change memory without the need for complicated manufacturing procedures or iterative programming operations.
