The rare earth Pr doped Ca1-xPrxMnO3 （x=0, 0.06, 0.08, 0.1, 0.12, and 0.14） compound bulk samples were prepared to study the effect of Pr doping on thermoelectric transport properties of CaMnO3 compound system. The ...The rare earth Pr doped Ca1-xPrxMnO3 （x=0, 0.06, 0.08, 0.1, 0.12, and 0.14） compound bulk samples were prepared to study the effect of Pr doping on thermoelectric transport properties of CaMnO3 compound system. The doped samples exhibited sin-gle phase composition within the experimental doping range, with condensed bulk microstructure and small porosities. The electrical resistivity was remarkably reduced for doped samples, on account of the enhanced carrier concentration;the absolute value of See-beck coefficient was deteriorated mainly due to enhanced electron carrier concentration. The electrical performances of the doped samples reflected by resistivity and Seebeck coefficient fluctuations were optimistically tuned, with an optimized power factor value of 0.342 mW/（m·K2） at 873 K for x=0.08 sample, which was very much higher comparing with that of the un-doped sample. The lattice thermal conduction was really confined, leading to distinctly repressed total thermal conductivity. The thermoelectric per-formance was noticeably improved by Pr doping and the dimensionless figure of merit ZT for the Ca0.92Pr0.08MnO3 compound was favorably optimized with the maximum value 0.16 at 873 K.展开更多
Pr3＋ doped ZnO quantum dots （QDs） were successfully synthesized by sol-gel process. X-ray diffraction （XRD） and X-ray Phtoelectron spectroscopy （XPS） were used to analyze the microstructure variation of ZnO QDs...Pr3＋ doped ZnO quantum dots （QDs） were successfully synthesized by sol-gel process. X-ray diffraction （XRD） and X-ray Phtoelectron spectroscopy （XPS） were used to analyze the microstructure variation of ZnO QDs and the chemical environment of Pr3＋ with increasing Pr3＋ doping concentrations. Most of Pr3＋ ions distribute on the surface ofZnO QDs while a few of them penetrate into the ZnO lattice to substitute Zn2＋ which causes the lattice distortion and the change of the crystal size. With increasing concentration of Pr3＋ ions, the crystal size of ZnO QDs firstly increases and then decreases meanwhile the amorphization gradually increases. New Pr-O-Zn bonds formed after Pr3＋ doping and Pr3＋ ions have at least two chemical bonding environments： one is Pr-O-Zn bond and the other is Pr-O bond surrounded by oxygen vacancies.展开更多
Herein,sodium dodecylbenzene sulfonate(SDBS)was used as a template to control the synthesis of Ca_(0.5)Pr_(0.5)FeO_(3).Its microstructure,composition,and morphology were detected via X-ray diffraction(XRD),Fourier tra...Herein,sodium dodecylbenzene sulfonate(SDBS)was used as a template to control the synthesis of Ca_(0.5)Pr_(0.5)FeO_(3).Its microstructure,composition,and morphology were detected via X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),and scanning electron microscopy(SEM).The properties of catalyzing bagasse lignin(BL)pyrolysis were determined by thermogravimetric analysis(TG)test and evaluation of a fixed bed alumina microreactor.The results show that the sample Ca_(0.5)Pr_(0.5)FeO_(3)regulated by SDBS has a cubic crystal phase,and the addition of SDBS does not cause phase transition.Moreover,when the SDBS concentration is 0.10 mol/L,the particle size is 200-500 nm and the specific surface area is 11.26 m^(2)/g.The yields of gas,liquid,and solid products in the BL catalytic pyrolysis are 39.58 wt%,26.76 wt%and 32.36 wt%,respectively.The contents of CO_(2)and CO decrease from 54.07%and 4.98%to 45.29%and 3.23%,respectively.The liquid products are mainly guaiacol,syringol,and phenol,and the total selectivity of phenols is 83.67%,accompanied by a small amount of non-aromatic oxygen-containing compounds(five-membered ring(furan)or ester).Compared with the BL pyrolysis and Ca_(0.5)Pr_(0.5)FeO_(3)catalytic pyrolysis products,the selectivity of guaiacol compounds increases by43.26%,while those of syringol compounds and phenylketones decrease by 30.08%and 3.39%,respectively.The selectivity of 2,6-dimethoxyphenol is 28.37%.After five catalytic pyrolysis-regeneration cycles,the characteristic peaks of the catalyst do not change significantly and the particles are uniform,suggesting that the catalyst has good crystal phase stability and regeneration stability.展开更多
Praseodymium（III） doped CeF3, CeF3：Gd, LaF3, GdF3 and YF3 inorganic fluorides were precipitated in an aqueous, sur- factant-free solution, using NH4F as a source of fluoride ions. The as-prepared products were subj...Praseodymium（III） doped CeF3, CeF3：Gd, LaF3, GdF3 and YF3 inorganic fluorides were precipitated in an aqueous, sur- factant-free solution, using NH4F as a source of fluoride ions. The as-prepared products were subjected to a hydrothermal treatment, which led to the formation of crystalline nanoluminophores, composed of spherical （30 nm） and elongated （40-200 nm） nanos- tructures. Due to the presence of Pr3＋ ions, the synthesized nanomaterials showed yellow luminescence under a blue light irradiation. The nanoluminophore based on the YF3 host revealed the most promising spectroscopic properties, i.e., bright and intensive emission, hence it was investigated in detail. The photophysical properties of the nanomaterials obtained were studied by powder X-ray diffrac- tion （XRD）, transmission electron microscopy （TEM） and spectrofluorometry, i.e., measurements of excitation/emission spectra and luminescence decay curves.展开更多
Single crystal of Lu2Si2OT：Pr was grown by Czochralski method. Transmittance, photoluminescence excitation （PLE） and photo- luminescence （PL） spectra, X-ray excited luminescence （XEL） and fluorescence decay tim...Single crystal of Lu2Si2OT：Pr was grown by Czochralski method. Transmittance, photoluminescence excitation （PLE） and photo- luminescence （PL） spectra, X-ray excited luminescence （XEL） and fluorescence decay time spectra of the sample were measured and dis- cussed to investigate its optical characteristics. The crystal structure of the as grown Lu2Si207：Pr was confirmed to be C2/m. There was a broad absorption peaking at 245 um in the region from 200-260 urn. The PL spectntm was dominated by fast 3py^3Hj band peaking at 524 nm. The XEL spectrum was dominated by the fast 5d14t^---~41e emission peaking at 265 nm. The 2D （temperature-intensity） and 3D （tem- perature-wavelength-intensity） thermally stimulated luminescence （TSL） spectra were measured. The Pr3＋ ion was found to be the recombina- tion center during the TSL process. Three obvious traps were detected in LPS：Pr single crystal with energy depth at 1.06, 0.78 and 0.67 eV.展开更多
The monomolecular surface layer of acceptor doped CeO_(2) may become neutral and metallic or charged and semiconducting.This is revealed in the theoretical analysis of the oxygen pressure dependence of the surface def...The monomolecular surface layer of acceptor doped CeO_(2) may become neutral and metallic or charged and semiconducting.This is revealed in the theoretical analysis of the oxygen pressure dependence of the surface defects concentration in acceptor doped ceria with two different dopant types and operated under different oxygen pressures.Recently published experimental data for highly reduced Sm0.2Ce0.8O1.9-x(SDC)containing a fixed valence dopant Sm3+are very different from those published for Pr0.1Ce0.9O_(2)-x(PCO) with the variable valence dopant Pr4+/Pr3+being reduced under milder conditions.The theoretical analysis of these experimental results fits very well the experimental results of SDC and PCO.It leads to the following predictions:the highly reduced surface of SDC is metallic and neutral,the metallic surface electron density of state is gs=0.9×10^(38)J-1·m^(-2)(1.4×1015eV^(-1)·cm^(-2)),the electron effective mass is meff,s=3.3me,and the phase diagram of the reduced surface has theα(fcc)structure as in the bulk.In PCO a double layer is predicted to be formed between the surface and the bulk with the surface being negatively charged and semiconducting.The surface of PCO maintains high Pr^(3+) defect concentration as well as relative high oxygen vacancy concentration at oxygen pressures higher than in the bulk.The reasons for the difference between a metallic and semiconducting surface layer of acceptor doped CeO_(2) are reviewed,as well as the key theoretical considerations applied in coping with this problem.For that we make use of the experimental data and theoretical analysis available for acceptor doped ceria.展开更多
The massive application of single crystal(SC)ternary cathode material LiNi_(1-x-y)Mn_(x)Co_(y)O_(2)is largely restricted by the unsatisfactory rate capability which is caused by the sluggish Li+diffusion and structura...The massive application of single crystal(SC)ternary cathode material LiNi_(1-x-y)Mn_(x)Co_(y)O_(2)is largely restricted by the unsatisfactory rate capability which is caused by the sluggish Li+diffusion and structural instability.Herein,Pr^(3+),a large radius ion is introduced to single-crystal LiNi_(0.5)Mn_(0.3)Co_(0.2)O_(2)to enhance Li^(+)conductivity and structural stability.With 0.4%Pr doping,the Li(Ni_(0.5)Mn_(0.3)Co_(0.2))_(0.996)Pr_(0.004)O_(2)cathode displays a capacity retention of 79.72%at 10 C,and a 98.17%capacity retention after 50 cycles at 25°C and 96.3%capacity retention after 50 cycles at 55°C within a 3.0–4.5 V voltage window.Electrochemical impedance spectroscopy confirms that the Pr doping can effectively lower the charge-transfer resistance and facilitate the transportation of Li^(+)on the surface of LiNi_(0.5)Mn_(0.3)Co_(0.2)O_(2).The Direct current internal resistance result implies that the structure of the Pr-doped cathode particles is more stable during cycling.In addition,differential scanning calorimetry measurements measurement combined with in situ X-ray diffraction confirms the thermo-stabilization effect of the Pr dopant.展开更多
Topological nodal-line semimetals attract growing research attention in the photonic and optoelectronic fields due to their unique topological energy-level bands and fascinating nonlinear optical responses.Here,to the...Topological nodal-line semimetals attract growing research attention in the photonic and optoelectronic fields due to their unique topological energy-level bands and fascinating nonlinear optical responses.Here,to the best of our knowledge,we first report the saturable absorption property of topological nodal-line semimetal HfGeTe and the related pulse modulation in passively Q-switched visible lasers.Few-layer HfGeTe demonstrates outstanding saturable absorption properties in the visible-light band,yielding the saturation intensities of 7.88,12.66,and 6.64μJ/cm^(2)at 515,640,and 720 nm,respectively.Based on an as-prepared few-layer HfGeTe optical switch and a Pr:LiYF_(4)gain medium,Q-switched visible lasers are also successfully achieved at 522,640,and 720 nm.The minimum pulse widths of the green,red,and deep-red pulsed lasers are150,125.5,and 420 ns,respectively.Especially for the green and red pulsed laser,the obtained pulse width is smaller than those of the low-dimensional layered materials.Our work sheds light on the application potential of topological nodal-line semimetals in the generation of visible pulsed lasers.展开更多
基金Project supported by National Natural Science Foundation of China(50801002)Beijing Municipal Natural Science Foundation(2112007)Basic and Advanced Technology Research Project of Henan Province(132300410071)
文摘The rare earth Pr doped Ca1-xPrxMnO3 （x=0, 0.06, 0.08, 0.1, 0.12, and 0.14） compound bulk samples were prepared to study the effect of Pr doping on thermoelectric transport properties of CaMnO3 compound system. The doped samples exhibited sin-gle phase composition within the experimental doping range, with condensed bulk microstructure and small porosities. The electrical resistivity was remarkably reduced for doped samples, on account of the enhanced carrier concentration;the absolute value of See-beck coefficient was deteriorated mainly due to enhanced electron carrier concentration. The electrical performances of the doped samples reflected by resistivity and Seebeck coefficient fluctuations were optimistically tuned, with an optimized power factor value of 0.342 mW/（m·K2） at 873 K for x=0.08 sample, which was very much higher comparing with that of the un-doped sample. The lattice thermal conduction was really confined, leading to distinctly repressed total thermal conductivity. The thermoelectric per-formance was noticeably improved by Pr doping and the dimensionless figure of merit ZT for the Ca0.92Pr0.08MnO3 compound was favorably optimized with the maximum value 0.16 at 873 K.
基金Funded by the Science and Technology Planning Project of Wuhan City(No.2013010501010135)the Science and Technology Planning Project of Hubei Province(Nos.2013BAA095,2014BAA136)National Natural Science Foundation of China(No.51372179)
文摘Pr3＋ doped ZnO quantum dots （QDs） were successfully synthesized by sol-gel process. X-ray diffraction （XRD） and X-ray Phtoelectron spectroscopy （XPS） were used to analyze the microstructure variation of ZnO QDs and the chemical environment of Pr3＋ with increasing Pr3＋ doping concentrations. Most of Pr3＋ ions distribute on the surface ofZnO QDs while a few of them penetrate into the ZnO lattice to substitute Zn2＋ which causes the lattice distortion and the change of the crystal size. With increasing concentration of Pr3＋ ions, the crystal size of ZnO QDs firstly increases and then decreases meanwhile the amorphization gradually increases. New Pr-O-Zn bonds formed after Pr3＋ doping and Pr3＋ ions have at least two chemical bonding environments： one is Pr-O-Zn bond and the other is Pr-O bond surrounded by oxygen vacancies.
基金Project supported by the National Natural Science Foundation of China(21908021)the Excellent Youth Foundation of Heilongjiang Province,China(JC2018002)the Youth Fund of Northeast Petroleum University(2018QNL-17)。
文摘Herein,sodium dodecylbenzene sulfonate(SDBS)was used as a template to control the synthesis of Ca_(0.5)Pr_(0.5)FeO_(3).Its microstructure,composition,and morphology were detected via X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),and scanning electron microscopy(SEM).The properties of catalyzing bagasse lignin(BL)pyrolysis were determined by thermogravimetric analysis(TG)test and evaluation of a fixed bed alumina microreactor.The results show that the sample Ca_(0.5)Pr_(0.5)FeO_(3)regulated by SDBS has a cubic crystal phase,and the addition of SDBS does not cause phase transition.Moreover,when the SDBS concentration is 0.10 mol/L,the particle size is 200-500 nm and the specific surface area is 11.26 m^(2)/g.The yields of gas,liquid,and solid products in the BL catalytic pyrolysis are 39.58 wt%,26.76 wt%and 32.36 wt%,respectively.The contents of CO_(2)and CO decrease from 54.07%and 4.98%to 45.29%and 3.23%,respectively.The liquid products are mainly guaiacol,syringol,and phenol,and the total selectivity of phenols is 83.67%,accompanied by a small amount of non-aromatic oxygen-containing compounds(five-membered ring(furan)or ester).Compared with the BL pyrolysis and Ca_(0.5)Pr_(0.5)FeO_(3)catalytic pyrolysis products,the selectivity of guaiacol compounds increases by43.26%,while those of syringol compounds and phenylketones decrease by 30.08%and 3.39%,respectively.The selectivity of 2,6-dimethoxyphenol is 28.37%.After five catalytic pyrolysis-regeneration cycles,the characteristic peaks of the catalyst do not change significantly and the particles are uniform,suggesting that the catalyst has good crystal phase stability and regeneration stability.
基金Project supported by the Polish National Science Centre(2015/17/N/ST5/01947)
文摘Praseodymium（III） doped CeF3, CeF3：Gd, LaF3, GdF3 and YF3 inorganic fluorides were precipitated in an aqueous, sur- factant-free solution, using NH4F as a source of fluoride ions. The as-prepared products were subjected to a hydrothermal treatment, which led to the formation of crystalline nanoluminophores, composed of spherical （30 nm） and elongated （40-200 nm） nanos- tructures. Due to the presence of Pr3＋ ions, the synthesized nanomaterials showed yellow luminescence under a blue light irradiation. The nanoluminophore based on the YF3 host revealed the most promising spectroscopic properties, i.e., bright and intensive emission, hence it was investigated in detail. The photophysical properties of the nanomaterials obtained were studied by powder X-ray diffrac- tion （XRD）, transmission electron microscopy （TEM） and spectrofluorometry, i.e., measurements of excitation/emission spectra and luminescence decay curves.
基金Project supported by National Natural Science Foundation of China(50902145,51171239)the Natural Science Foundation of Shanghai(09ZR1435800)the Knowledge Innovation Program of the Chinese Academy of Sciences(SCX200701)
文摘Single crystal of Lu2Si2OT：Pr was grown by Czochralski method. Transmittance, photoluminescence excitation （PLE） and photo- luminescence （PL） spectra, X-ray excited luminescence （XEL） and fluorescence decay time spectra of the sample were measured and dis- cussed to investigate its optical characteristics. The crystal structure of the as grown Lu2Si207：Pr was confirmed to be C2/m. There was a broad absorption peaking at 245 um in the region from 200-260 urn. The PL spectntm was dominated by fast 3py^3Hj band peaking at 524 nm. The XEL spectrum was dominated by the fast 5d14t^---~41e emission peaking at 265 nm. The 2D （temperature-intensity） and 3D （tem- perature-wavelength-intensity） thermally stimulated luminescence （TSL） spectra were measured. The Pr3＋ ion was found to be the recombina- tion center during the TSL process. Three obvious traps were detected in LPS：Pr single crystal with energy depth at 1.06, 0.78 and 0.67 eV.
基金financially supported by the Technion V.P.for Research Fund(No.2023320)。
文摘The monomolecular surface layer of acceptor doped CeO_(2) may become neutral and metallic or charged and semiconducting.This is revealed in the theoretical analysis of the oxygen pressure dependence of the surface defects concentration in acceptor doped ceria with two different dopant types and operated under different oxygen pressures.Recently published experimental data for highly reduced Sm0.2Ce0.8O1.9-x(SDC)containing a fixed valence dopant Sm3+are very different from those published for Pr0.1Ce0.9O_(2)-x(PCO) with the variable valence dopant Pr4+/Pr3+being reduced under milder conditions.The theoretical analysis of these experimental results fits very well the experimental results of SDC and PCO.It leads to the following predictions:the highly reduced surface of SDC is metallic and neutral,the metallic surface electron density of state is gs=0.9×10^(38)J-1·m^(-2)(1.4×1015eV^(-1)·cm^(-2)),the electron effective mass is meff,s=3.3me,and the phase diagram of the reduced surface has theα(fcc)structure as in the bulk.In PCO a double layer is predicted to be formed between the surface and the bulk with the surface being negatively charged and semiconducting.The surface of PCO maintains high Pr^(3+) defect concentration as well as relative high oxygen vacancy concentration at oxygen pressures higher than in the bulk.The reasons for the difference between a metallic and semiconducting surface layer of acceptor doped CeO_(2) are reviewed,as well as the key theoretical considerations applied in coping with this problem.For that we make use of the experimental data and theoretical analysis available for acceptor doped ceria.
基金Financial supports from National Natural Science Foundation of China(51872027)Beijing Natural Science Foundation(Z200011)are gratefully acknowledged。
文摘The massive application of single crystal(SC)ternary cathode material LiNi_(1-x-y)Mn_(x)Co_(y)O_(2)is largely restricted by the unsatisfactory rate capability which is caused by the sluggish Li+diffusion and structural instability.Herein,Pr^(3+),a large radius ion is introduced to single-crystal LiNi_(0.5)Mn_(0.3)Co_(0.2)O_(2)to enhance Li^(+)conductivity and structural stability.With 0.4%Pr doping,the Li(Ni_(0.5)Mn_(0.3)Co_(0.2))_(0.996)Pr_(0.004)O_(2)cathode displays a capacity retention of 79.72%at 10 C,and a 98.17%capacity retention after 50 cycles at 25°C and 96.3%capacity retention after 50 cycles at 55°C within a 3.0–4.5 V voltage window.Electrochemical impedance spectroscopy confirms that the Pr doping can effectively lower the charge-transfer resistance and facilitate the transportation of Li^(+)on the surface of LiNi_(0.5)Mn_(0.3)Co_(0.2)O_(2).The Direct current internal resistance result implies that the structure of the Pr-doped cathode particles is more stable during cycling.In addition,differential scanning calorimetry measurements measurement combined with in situ X-ray diffraction confirms the thermo-stabilization effect of the Pr dopant.
基金supported by the National Key Research and Development Program of China(No.2021YFB3601504)the National Natural Science Foundation of China(Nos.52025021and 92163207)+1 种基金the Natural Science Foundation of Shandong Province(No.ZR2022LLZ005)the Future Plans of Young Scholars at Shandong University。
文摘Topological nodal-line semimetals attract growing research attention in the photonic and optoelectronic fields due to their unique topological energy-level bands and fascinating nonlinear optical responses.Here,to the best of our knowledge,we first report the saturable absorption property of topological nodal-line semimetal HfGeTe and the related pulse modulation in passively Q-switched visible lasers.Few-layer HfGeTe demonstrates outstanding saturable absorption properties in the visible-light band,yielding the saturation intensities of 7.88,12.66,and 6.64μJ/cm^(2)at 515,640,and 720 nm,respectively.Based on an as-prepared few-layer HfGeTe optical switch and a Pr:LiYF_(4)gain medium,Q-switched visible lasers are also successfully achieved at 522,640,and 720 nm.The minimum pulse widths of the green,red,and deep-red pulsed lasers are150,125.5,and 420 ns,respectively.Especially for the green and red pulsed laser,the obtained pulse width is smaller than those of the low-dimensional layered materials.Our work sheds light on the application potential of topological nodal-line semimetals in the generation of visible pulsed lasers.
