The electronic structure,densities of states and optical properties of the stable orthorhombic BaSi2 have been calculated using the first-principle density function theory and pseudopotential method. The results show ...The electronic structure,densities of states and optical properties of the stable orthorhombic BaSi2 have been calculated using the first-principle density function theory and pseudopotential method. The results show that BaSi2 is an indirect semiconductor with the band gap of 1.086 eV,the valence bands of BaSi2 are mainly composed of Si 3p,3s and Ba 5d,and the conduction bands are mainly composed of Ba 6s,5d as well as Si 3p. The static dielectric function ε1(0) is 11.17,the reflectivity n0 is 3.35,and the biggest peak of the absorption coefficient is 2.15×105 cm-1.展开更多
In this paper,Dy^(3+)incorporated BaSi_(2)O_(5)phosphors were synthesized by gel co mbustion method and characterized by X-ray diffraction(XRD).The effects of various heating rate s on thermoluminescence(TL)kinetics a...In this paper,Dy^(3+)incorporated BaSi_(2)O_(5)phosphors were synthesized by gel co mbustion method and characterized by X-ray diffraction(XRD).The effects of various heating rate s on thermoluminescence(TL)kinetics and glow peak temperatures of Dy^(3+)incorporated BaSi_(2)O_(5)phosphors exposed toβirradiation at room temperature were investigated.The glow curves of the phosphor exposed toβ-irradiation(0.1-100 Gy)consist of four main peaks located at 87,130,271,and 327℃and exhibit a good linearity between 0.1 and100 Gy.Three experimental techniques including variable heating rate(VHR),repeated initial rise(RIR),peak shape(PS)and computerized glow curve deconvolution(CGCD)were employed to determine TL kinetic parameters.Our findings indicate that the TL glow peaks of the phosphor obey first-order kinetics.Analysis of the main dosimetric peaks through the techniques mentio ned above indicates that activation energies(E)and pre-exponential factor(s)are in the range of 0.80-1.50 eV and 1.15×10^(8)-3.28×10^(13)s^(-1).Additionally,it is found that the temperature of the glow peaks shifts toward the higher temperatures and the TL intensity smoothly decreases as the heating rate increases.The effect on the TL intensities and glow peak temperatu res of the heating rate is discussed in terms of thermal quenching.展开更多
As a cyan-emitting oxonitridosilicate phosphor,BaSi_(2)O_(2)N_(2):Eu^(2+)can be used as a competent cyan compensator to improve the color rendering index of white light-emitting diodes(WLEDs).However,low luminescence ...As a cyan-emitting oxonitridosilicate phosphor,BaSi_(2)O_(2)N_(2):Eu^(2+)can be used as a competent cyan compensator to improve the color rendering index of white light-emitting diodes(WLEDs).However,low luminescence efficiency and poor thermal stability of this type of phosphor seriously suppress its actual application in full-spectrum lighting.The replacements of Ba^(2+)by Lu^(3+)and Ba^(2+)-Si^(4+)by Lu^(3+)-Al^(3+)can greatly increase the luminescence intensity and improve the thermal stability at the same time.With Lu^(3+)doping,the internal quantum efficiencyηIQE Ba_(0.925)Si_(2)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+)is 24.08%higher than that of Ba_(0.97)Si_(2)O_(2)N_(2):0.03 Eu^(2+).After Al^(3+)co-doping,theηIQE is further increased by 10.31%compared to Ba_(0.925)Si_(2)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+).When the temperature rises to 473 K,the luminescence intensity of Ba_(0.925)Si_(2)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+)maintains 62.32%of that at room temperature,which increases by 17.35%in relative to the Ba_(0.97)Si_(2)O_(2)N_(2):0.03 Eu^(2+),while the luminescence intensity of Ba_(0.925)Si_(1.97)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+),0.03 Al^(3+)keeps 73.87%of the initial value,which increases by18.52%compared to Ba_(0.925)Si_(2)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+).The mechanisms for luminescence and thermal stability improvement are proposed.The Ba_(0.925)Si_(1.97)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+),0.03 Al^(3+)cyan phosphor,Y3 Al5 O12:Ce3+yellow phosphor and CaAlSiN3:Eu^(2+)red phosphor are mixed thoroughly and coated on a blue LED(450 nm)to assemble a WLED.The WLED demonstrates a color rendering index(Ra)of 97.1 at150 mA,and the R1-R15 values are all above 90.The results indicate that as an effective cyan compensator in WLED,the BaSi_(2)O_(2)N_(2):Eu^(2+),Lu^(3+),Al^(3+)phosphor has great application prospect in the field of full-spectrum lighting.展开更多
基金Supported by the National Natural Science Foundation of China (Grant Nos. 60566001 and 60766002)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20050657003)+3 种基金the Scientific Research Foundation for the Returned Overseas Chinese Scholars, Ministry of Education of China (Grant No. (2005)383)the Specialized Fund of Nomarch for Excellent Talent of Science and Technology of Guizhou Province (Grant No. Z053114)the Scientific and Technological Projects for the Returned Overseas of Guizhou Province (Grant No. (2004)03)the Top Talent's Scientific Research Project of Organization Department of Guizhou Province (Grant No. Z053123)
文摘The electronic structure,densities of states and optical properties of the stable orthorhombic BaSi2 have been calculated using the first-principle density function theory and pseudopotential method. The results show that BaSi2 is an indirect semiconductor with the band gap of 1.086 eV,the valence bands of BaSi2 are mainly composed of Si 3p,3s and Ba 5d,and the conduction bands are mainly composed of Ba 6s,5d as well as Si 3p. The static dielectric function ε1(0) is 11.17,the reflectivity n0 is 3.35,and the biggest peak of the absorption coefficient is 2.15×105 cm-1.
基金Project supported by the Deanship of Scientific Research at Jazan University,the Kingdom of Saudi Arabia(W41-032).
文摘In this paper,Dy^(3+)incorporated BaSi_(2)O_(5)phosphors were synthesized by gel co mbustion method and characterized by X-ray diffraction(XRD).The effects of various heating rate s on thermoluminescence(TL)kinetics and glow peak temperatures of Dy^(3+)incorporated BaSi_(2)O_(5)phosphors exposed toβirradiation at room temperature were investigated.The glow curves of the phosphor exposed toβ-irradiation(0.1-100 Gy)consist of four main peaks located at 87,130,271,and 327℃and exhibit a good linearity between 0.1 and100 Gy.Three experimental techniques including variable heating rate(VHR),repeated initial rise(RIR),peak shape(PS)and computerized glow curve deconvolution(CGCD)were employed to determine TL kinetic parameters.Our findings indicate that the TL glow peaks of the phosphor obey first-order kinetics.Analysis of the main dosimetric peaks through the techniques mentio ned above indicates that activation energies(E)and pre-exponential factor(s)are in the range of 0.80-1.50 eV and 1.15×10^(8)-3.28×10^(13)s^(-1).Additionally,it is found that the temperature of the glow peaks shifts toward the higher temperatures and the TL intensity smoothly decreases as the heating rate increases.The effect on the TL intensities and glow peak temperatu res of the heating rate is discussed in terms of thermal quenching.
基金Project supported by the National Natural Science Foundation of China(51962005)the Cultivation Project of the State Key Laboratory of Green Development and High-value Utilization of Ionic Rare Earth Resources in Jiangxi Province(20194AFD44003)+3 种基金the Key Research and Development Plan Project of Jiangxi Province(20192ACB50021)Natural Science Foundation of Jiangxi Province(20192BAB206010)Key Special Project of Science and Technology to Help Economy in Jiangxi Province([2020]87)Youth Jinggang Scholars Program in Jiangxi Province([2018]82)。
文摘As a cyan-emitting oxonitridosilicate phosphor,BaSi_(2)O_(2)N_(2):Eu^(2+)can be used as a competent cyan compensator to improve the color rendering index of white light-emitting diodes(WLEDs).However,low luminescence efficiency and poor thermal stability of this type of phosphor seriously suppress its actual application in full-spectrum lighting.The replacements of Ba^(2+)by Lu^(3+)and Ba^(2+)-Si^(4+)by Lu^(3+)-Al^(3+)can greatly increase the luminescence intensity and improve the thermal stability at the same time.With Lu^(3+)doping,the internal quantum efficiencyηIQE Ba_(0.925)Si_(2)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+)is 24.08%higher than that of Ba_(0.97)Si_(2)O_(2)N_(2):0.03 Eu^(2+).After Al^(3+)co-doping,theηIQE is further increased by 10.31%compared to Ba_(0.925)Si_(2)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+).When the temperature rises to 473 K,the luminescence intensity of Ba_(0.925)Si_(2)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+)maintains 62.32%of that at room temperature,which increases by 17.35%in relative to the Ba_(0.97)Si_(2)O_(2)N_(2):0.03 Eu^(2+),while the luminescence intensity of Ba_(0.925)Si_(1.97)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+),0.03 Al^(3+)keeps 73.87%of the initial value,which increases by18.52%compared to Ba_(0.925)Si_(2)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+).The mechanisms for luminescence and thermal stability improvement are proposed.The Ba_(0.925)Si_(1.97)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+),0.03 Al^(3+)cyan phosphor,Y3 Al5 O12:Ce3+yellow phosphor and CaAlSiN3:Eu^(2+)red phosphor are mixed thoroughly and coated on a blue LED(450 nm)to assemble a WLED.The WLED demonstrates a color rendering index(Ra)of 97.1 at150 mA,and the R1-R15 values are all above 90.The results indicate that as an effective cyan compensator in WLED,the BaSi_(2)O_(2)N_(2):Eu^(2+),Lu^(3+),Al^(3+)phosphor has great application prospect in the field of full-spectrum lighting.
