Both the band filling effect and Fe/Mo disorder have a close correlation with the physical properties of the double perovskite Ca2FeMoO6. Two series of Ca2FeMoO6and Nd0.3Ca1.7FeMoO6ceramics sintered at(1050℃, 1200℃,...Both the band filling effect and Fe/Mo disorder have a close correlation with the physical properties of the double perovskite Ca2FeMoO6. Two series of Ca2FeMoO6and Nd0.3Ca1.7FeMoO6ceramics sintered at(1050℃, 1200℃, and 1300℃) were specially designed to comparatively investigate the band-filling effect and Fe/Mo disorder on the physical properties of Ca2FeMoO6. The x-ray diffraction indicates that Fe/Mo disorder is sensitive to the sintering temperature. The magnetization behavior is mainly controlled by the Fe/Mo disorder not by the band filling effect, manifested by a close correlation of saturated magnetization(Ms) with the Fe/Mo disorder. Interestingly, magnetoresistance(MR) property of the same composition is dominantly contributed by the grain boundary strength, which can be expressed by the macroscopic resistivity values. However, the band filling effect caused by the Nd-substitution can decrease the spin polarization, and thus suppress the MR performance fundamentally. Contrary to the MR response, the Curie temperature(TC) shows an obvious optimization due to the band filling effect, which increases the carrier density near the Fermi level responsible for the ferromagnetic coupling interaction strengthen. Maybe, our work can provoke further research interests into the correlation of the band-filling effects and Fe/Mo disorder with the physical properties of other Fe/Mo-based double perovskites.展开更多
A novel red-emitting phosphor tantalate Ca_(2)YTaO_(6):Eu^(3+)was synthesized by a solid-state reaction.The purity and surface morphology of the phosphors were characterized.The Ca_(2)YTaO_(6):Eu^(3+)phosphors show a ...A novel red-emitting phosphor tantalate Ca_(2)YTaO_(6):Eu^(3+)was synthesized by a solid-state reaction.The purity and surface morphology of the phosphors were characterized.The Ca_(2)YTaO_(6):Eu^(3+)phosphors show a sharp emission peak at 612 nm under near-ultraviolet(n-UV) at 395 nm because of the ^(5)D0→^(7)F_(2) transition of Eu^(3+).The optimal Eu^(3+)doping concentration in Ca_(2)YTaO_(6) is 40 mol% and the critical energy-transfer distance of Eu^(3+)ions was calculated to be 0.9 nm.The emission spectra of Ca_(2)YTaO_(6):Eu_(3+)from 300 to 480 K were investigated.The thermal-quenching temperature(T_(0.5)) of Ca_(2)YTaO_(6):Eu^(3+)is above 480 K.The color purity of Ca_(2)YTaO_(6):40 mol%Eu^(3+)is as high as 99.8%.The luminescence lifetime of Ca_(2)YTaO_(6):40 mol%Eu^(3+)was also discussed.The high color purity and high thermal stability of Eu^(3+)-doped Ca_(2)YTaO_(6) phosphors contribute to its application value in white lightemitting diodes(w-LEDs).展开更多
Bright Eu3+-activated double-perovskite Sr2LaTaO6 red-emitting phosphors were successfully synthesized by a high-temperature solid-state method. Under near-ultraviolet excitation at 394 nm, optimal Sr2LaTaO6∶0.2 Eu3+...Bright Eu3+-activated double-perovskite Sr2LaTaO6 red-emitting phosphors were successfully synthesized by a high-temperature solid-state method. Under near-ultraviolet excitation at 394 nm, optimal Sr2LaTaO6∶0.2 Eu3+phosphors emitted high-brightness red light around 613 nm with the International Commission on Illumination chromaticity coordinates(0.650,0.349). Notably, the color purity can reach 92%. Impressively, the favorable thermal stability of the Sr2LaTaO6∶0.2 Eu3+phosphors was characterized by temperature-dependent emission spectra at different temperatures from 303 to 463 K, and the emission intensity at 423 K remained 73% of its value at 303 K. All of the results suggested that the as-prepared Sr2LaTaO6∶0.2 Eu3+phosphors can be used in near-ultraviolet-excitable white light-emitting diodes as a red-emitting color converter.展开更多
Novel yellow-emitting phosphors of Dy^(3+)-doped double perovskite Ca_(2)MgTeO_(6) were synthesized by using a conventional high-temperature solid-state reaction.The phase purity,particle morphology,size distribution,...Novel yellow-emitting phosphors of Dy^(3+)-doped double perovskite Ca_(2)MgTeO_(6) were synthesized by using a conventional high-temperature solid-state reaction.The phase purity,particle morphology,size distribution,elemental composition,luminescence properties,and luminescence decay curves of the resulting products were then analyzed in detail.The Ca_(2)MgTeO_(6):Dy^(3+),Na^(+) phosphors show three emission peaks after near-ultraviolet excitation at 350 nm,which correspond to ^(4)F_(9/2)→^(6)H_(11/2),^(4)F_(9/2)→^(6)H_(13/2),and ^(4)F_(9/2)→^(6)H_(13/2) transitions,respectively.Among them,the strongest peak is observed at 573 nm.The best doping content of Dy^(3+)in Ca_(2)MgTeO_(6):xDy^(3+),xNa^(+) phosphors is x=5 mol%.The calculated critical distance of energy transfer between Dy^(3+) ions is 1.6 nm.Luminescence quenching is confirmed to be due to dipole-dipole interactions among Dy^(3+) ions.The phosphors show excellent thermal stability with high activation energy(0.27 eV).The Commission Internationale de l’Eclairage(CIE) chromaticity coordinates of the Ca_(2)MgTeO_(6) Dy^(3+),Na^(+) phosphors are located in the yellow region.White light-emitting diodes(w-LEDs) were fabricated with a high color rendering index(R_(a)) of 88 and a good correlated color temperature(CCT) of 5440 K.All observed properties indicate that Ca_(2)MgTeO_(6):Dy^(3+),Na^(+) phosphors have potential applications in display and photonic devices.展开更多
Hydrothermal treatment of calcium oxide and boric acid mixtures at temperaturesbetween 234 ℃ and 300 ℃ has produced a colorless, transparent, orthorhombic compound Ca2B6O11 · H2O. Of the seven known members of ...Hydrothermal treatment of calcium oxide and boric acid mixtures at temperaturesbetween 234 ℃ and 300 ℃ has produced a colorless, transparent, orthorhombic compound Ca2B6O11 · H2O. Of the seven known members of the series of hydrated dicalcium hexaborate containing boron-oxygen six-membered ring anionic group (B3O8)7, only the title compound has been found to have the nonlinear optical effect. The second harmanic generation (SHG) effect of its crystal is larger than that of KH2PO4 (KDP). The reflection spectrum has shown that this compound has no absorption in the experimental wavelength range (800-240 nm). Its crystal structure is favorable for generating the nonlinear optical effect.展开更多
基金financially supported by the National Natural Science Foundation of China (Grant No. 51862012)the Natural Science Foundation of Jiangxi Province (Grants No. 20202BAB204008, 20165ABC28010)the Innovation Leadership Program of Ganzhou。
基金Project supported by the National Natural Science Foundation of China(Grant No.U1504107)the Doctoral Scientific Research Foundation(Grant No.qd15214)
文摘Both the band filling effect and Fe/Mo disorder have a close correlation with the physical properties of the double perovskite Ca2FeMoO6. Two series of Ca2FeMoO6and Nd0.3Ca1.7FeMoO6ceramics sintered at(1050℃, 1200℃, and 1300℃) were specially designed to comparatively investigate the band-filling effect and Fe/Mo disorder on the physical properties of Ca2FeMoO6. The x-ray diffraction indicates that Fe/Mo disorder is sensitive to the sintering temperature. The magnetization behavior is mainly controlled by the Fe/Mo disorder not by the band filling effect, manifested by a close correlation of saturated magnetization(Ms) with the Fe/Mo disorder. Interestingly, magnetoresistance(MR) property of the same composition is dominantly contributed by the grain boundary strength, which can be expressed by the macroscopic resistivity values. However, the band filling effect caused by the Nd-substitution can decrease the spin polarization, and thus suppress the MR performance fundamentally. Contrary to the MR response, the Curie temperature(TC) shows an obvious optimization due to the band filling effect, which increases the carrier density near the Fermi level responsible for the ferromagnetic coupling interaction strengthen. Maybe, our work can provoke further research interests into the correlation of the band-filling effects and Fe/Mo disorder with the physical properties of other Fe/Mo-based double perovskites.
基金The work was supported by Undergraduate Innovation Fund of Northwest A&F UniversityChina(201910712069)+3 种基金Hunan Provincial Key Laboratory of Xiangnan Rare-Precious Metals Compounds and Applications(2019XGJSKFJJ01)the Construction Program of the key discipline in Hunan Provincethe Projects of the Education Department of Hunan Province(No.18A465)Science and Technology Plan Project of Chenzhou City(jsyf2017014)。
文摘A novel red-emitting phosphor tantalate Ca_(2)YTaO_(6):Eu^(3+)was synthesized by a solid-state reaction.The purity and surface morphology of the phosphors were characterized.The Ca_(2)YTaO_(6):Eu^(3+)phosphors show a sharp emission peak at 612 nm under near-ultraviolet(n-UV) at 395 nm because of the ^(5)D0→^(7)F_(2) transition of Eu^(3+).The optimal Eu^(3+)doping concentration in Ca_(2)YTaO_(6) is 40 mol% and the critical energy-transfer distance of Eu^(3+)ions was calculated to be 0.9 nm.The emission spectra of Ca_(2)YTaO_(6):Eu_(3+)from 300 to 480 K were investigated.The thermal-quenching temperature(T_(0.5)) of Ca_(2)YTaO_(6):Eu^(3+)is above 480 K.The color purity of Ca_(2)YTaO_(6):40 mol%Eu^(3+)is as high as 99.8%.The luminescence lifetime of Ca_(2)YTaO_(6):40 mol%Eu^(3+)was also discussed.The high color purity and high thermal stability of Eu^(3+)-doped Ca_(2)YTaO_(6) phosphors contribute to its application value in white lightemitting diodes(w-LEDs).
基金supported by the National Natural Science Foundation of China (No. 51502190)Young Sanjin Scholars Distinguished Professor Program of Shanxi Province+1 种基金Open Fund of the State Key Laboratory of Luminescent Materials and Devices (South China University of Technology, No. 2020-skllmd-01)Graduate Education Innovation Project of Shanxi Province。
文摘Bright Eu3+-activated double-perovskite Sr2LaTaO6 red-emitting phosphors were successfully synthesized by a high-temperature solid-state method. Under near-ultraviolet excitation at 394 nm, optimal Sr2LaTaO6∶0.2 Eu3+phosphors emitted high-brightness red light around 613 nm with the International Commission on Illumination chromaticity coordinates(0.650,0.349). Notably, the color purity can reach 92%. Impressively, the favorable thermal stability of the Sr2LaTaO6∶0.2 Eu3+phosphors was characterized by temperature-dependent emission spectra at different temperatures from 303 to 463 K, and the emission intensity at 423 K remained 73% of its value at 303 K. All of the results suggested that the as-prepared Sr2LaTaO6∶0.2 Eu3+phosphors can be used in near-ultraviolet-excitable white light-emitting diodes as a red-emitting color converter.
基金Project supported by the Natural Science Foundation of Shaanxi Province(2018JM5055)Hunan Provincial Key Laboratory of Xiangnan Rare-Precious Metals Compounds and Applications(2019XGJSKFJJ01)+2 种基金the Construction Program of the Key Discipline in Hunan Provincethe Projects of the Education Department of Hunan Province(18A465)Science and Technology Plan Project of Chenzhou City(jsyf2017014)。
文摘Novel yellow-emitting phosphors of Dy^(3+)-doped double perovskite Ca_(2)MgTeO_(6) were synthesized by using a conventional high-temperature solid-state reaction.The phase purity,particle morphology,size distribution,elemental composition,luminescence properties,and luminescence decay curves of the resulting products were then analyzed in detail.The Ca_(2)MgTeO_(6):Dy^(3+),Na^(+) phosphors show three emission peaks after near-ultraviolet excitation at 350 nm,which correspond to ^(4)F_(9/2)→^(6)H_(11/2),^(4)F_(9/2)→^(6)H_(13/2),and ^(4)F_(9/2)→^(6)H_(13/2) transitions,respectively.Among them,the strongest peak is observed at 573 nm.The best doping content of Dy^(3+)in Ca_(2)MgTeO_(6):xDy^(3+),xNa^(+) phosphors is x=5 mol%.The calculated critical distance of energy transfer between Dy^(3+) ions is 1.6 nm.Luminescence quenching is confirmed to be due to dipole-dipole interactions among Dy^(3+) ions.The phosphors show excellent thermal stability with high activation energy(0.27 eV).The Commission Internationale de l’Eclairage(CIE) chromaticity coordinates of the Ca_(2)MgTeO_(6) Dy^(3+),Na^(+) phosphors are located in the yellow region.White light-emitting diodes(w-LEDs) were fabricated with a high color rendering index(R_(a)) of 88 and a good correlated color temperature(CCT) of 5440 K.All observed properties indicate that Ca_(2)MgTeO_(6):Dy^(3+),Na^(+) phosphors have potential applications in display and photonic devices.
文摘Hydrothermal treatment of calcium oxide and boric acid mixtures at temperaturesbetween 234 ℃ and 300 ℃ has produced a colorless, transparent, orthorhombic compound Ca2B6O11 · H2O. Of the seven known members of the series of hydrated dicalcium hexaborate containing boron-oxygen six-membered ring anionic group (B3O8)7, only the title compound has been found to have the nonlinear optical effect. The second harmanic generation (SHG) effect of its crystal is larger than that of KH2PO4 (KDP). The reflection spectrum has shown that this compound has no absorption in the experimental wavelength range (800-240 nm). Its crystal structure is favorable for generating the nonlinear optical effect.
