Mn-rich LiFe_(1-x)Mn_(x)PO_(4)(x>0.5),which combines the high operation voltage of LiMnPO_(4)with excellent rate performa nce of LiFePO4,is hindered by its sluggish kinetic properties.Herein,thermodynamic equilibri...Mn-rich LiFe_(1-x)Mn_(x)PO_(4)(x>0.5),which combines the high operation voltage of LiMnPO_(4)with excellent rate performa nce of LiFePO4,is hindered by its sluggish kinetic properties.Herein,thermodynamic equilibrium analysis of Mn^(2+)-Fe^(2+)-Mg^(2+)-C_(2)O_(4)^(2-)-H_(2)O system is used to guide the design and preparation of insitu Mg-doped(Fe_(0.4)Mn_(0.6))_(1-x)Mg_(x)C_(2)O_(4)intermediate,which is then employed as an innovative precursor to synthesize high-performance Mg-doped LiFe_(0.4)Mn_(0.6)PO_(4).It indicates that the metal ions with a high precipitation efficiency and the stoichiometric precursors with uniform element distribution can be achieved under the optimized thermodynamic conditions.Meanwhile,accelerated Li+diffusivity and reduced charge transfer resistance originating from Mg doping are verified by various kinetic characterizations.Benefiting from the contributions of inherited homogeneous element distribution,small particle size,uniform carbon layer coating,enhanced Li+migration ability and structural stability induced by Mg doping,the Li(Fe_(0.4)Mn_(0.6))_(0.97)Mg_(0.03)PO_(4)/C exhibits splendid electrochemical performance.展开更多
The Mg acceptor activation mechanism and hole transport characteristics in AlGaN alloy with Mg doping concentration(~ 1020 cm-3) grown by metal–organic chemical vapor deposition(MOCVD) are systematically studied thro...The Mg acceptor activation mechanism and hole transport characteristics in AlGaN alloy with Mg doping concentration(~ 1020 cm-3) grown by metal–organic chemical vapor deposition(MOCVD) are systematically studied through optical and electrical properties. Emission lines of shallow oxygen donors and(VⅢ complex)1- as well as VN3+ and neutral Mg acceptors are observed, which indicate that self-compensation is occurred in Mg-doped AlGaN at highly doping levels. The fitting of the temperature-dependent Hall effect data shows that the acceptor activation energy values in Mgdoped AlxGa1-xN(x = 0.23, 0.35) are 172 meV and 242 meV, and the hole concentrations at room temperature are 1.2×1018 cm-3 and 3.3× 1017 cm-3, respectively. Therefore, it is believed that there exists the combined effect of the Coulomb potentials of the dopants and screening of the Coulomb potentials by a high hole concentration. Moreover, due to the high ionized acceptors’ concentration and compensation ratio, the impurity conduction becomes more prominent and the valence band mobility drops sharply at low temperature.展开更多
The layered LiNi0.6Co0.2-xMn0.2MgxO2 （x=0.00,0.03,0.05,0.07） cathode materials were prepared by a co-precipitation method.The properties of the Mg-doped LiNi0.6Co0.2Mn0.2O2 were investigated by X-ray diffraction （...The layered LiNi0.6Co0.2-xMn0.2MgxO2 （x=0.00,0.03,0.05,0.07） cathode materials were prepared by a co-precipitation method.The properties of the Mg-doped LiNi0.6Co0.2Mn0.2O2 were investigated by X-ray diffraction （XRD）,scanning electron microscopy （SEM）,and electrochemical measurements.XRD studies showed that the Mg-doped LiNi0.6Co0.2Mn0.2O2 had the same layered structure as the undoped LiNi0.6Co0.2Mn0.2O2.The SEM images exhibited that the particle size of Mg-doped LiNi0.6Co0.2Mn0.2O2 was finer than that of the undoped LiNi0.6Co0.2 Mn0.2O2 and that the smallest particle size is only about 1μm.The Mg-doped LiNi0.6Co0.2Mn0.2O2 samples were investigated on the Li extraction/insertion performances through charge/discharge,cyclic voltammogram （CV）,and electrochemical impedance spectra（EIS）.The optimal doping content of Mg was that x= 0.03 in the LiNi0.6Co0.2-xMn0.2MgxO2 samples to achieve high discharge capacity and good cyclic stability.The electrode reaction reversibility and electronic conductivity was enhanced,and the charge transfer resistance was decreased through Mg-doping.The improved electrochemical performances of the Mg-doped LiNi0.6Co0.2Mn0.2O2 cathode materials are attributed to the addition of Mg 2＋ ion by stabilizing the layer structure.展开更多
The microstructure and performance of Li4Ti5O12 doped by Mg prepared by hydrothermal method and solid phase method were investigated. Lithium dihydrate, magnesium acetate and tetrabutyl titanate were used as the main ...The microstructure and performance of Li4Ti5O12 doped by Mg prepared by hydrothermal method and solid phase method were investigated. Lithium dihydrate, magnesium acetate and tetrabutyl titanate were used as the main raw materials. This study reveals that Mg^2+ has influences on the spherical structure, crystal development of Li4Ti5O12 and the electrochemical performances. The hollow spherical structure is composed of nano-sheet structure and the nano-sheet structure can be affected by the Mg^2+ content. For Li4-xMgxTi5 O12, the sheet structure can be refined with the increment of Mg^2+ content when x value is 0-0.1 and coarsen with the increment of Mg^2+ content when x value is 0.1-0.2. The hollow spherical Li4Ti5O12 powders prepared by hydrothermal method have better performance. The optimal Mgdoped amount of hydrothermal method is 0.1. At 0.1 C, the first discharge capacity of Li3.9Mg0.1Ti5O12 prepared through hydrothermal method at 0.1 C and 10 cycles is 182 and 178 mA hg^-1, respectively.展开更多
We report a GaInP/GaAs tandem solar cell with a novel GaAs tunnel junction（TJ） with using tellurium（Te） and magnesium（Mg） as n- and p-type dopants via dual-filament low temperature effusion cells grown by molecu...We report a GaInP/GaAs tandem solar cell with a novel GaAs tunnel junction（TJ） with using tellurium（Te） and magnesium（Mg） as n- and p-type dopants via dual-filament low temperature effusion cells grown by molecular beam epitaxy（MBE） at low temperature. The test Te/Mg-doped GaAs TJ shows a peak current density of 21 A/cm2. The tandem solar cell by the Te/Mg TJ shows a short-circuit current density of 12 m A/cm2, but a low open-circuit voltage range of1.4 V^1.71 V under AM1.5 illumination. The secondary ion mass spectroscopy（SIMS） analysis reveals that the Te doping is unexpectedly high and its doping profile extends to the Mg doping region, thus possibly resulting in a less abrupt junction with no tunneling carriers effectively. Furthermore, the tunneling interface shifts from the intended Ga As n＋＋/p＋＋junction to the AlGaInP/GaAs junction with a higher bandgap AlGaInP tunneling layers, thereby reducing the tunneling peak. The Te concentration of ~ 2.5 × 1020 in GaAs could cause a lattice strain of 10-3 in magnitude and thus a surface roughening,which also negatively influences the subsequent growth of the top subcell and the GaAs contacting layers. The doping features of Te and Mg are discussed to understand the photovoltaic response of the studied tandem cell.展开更多
Mg PSZ ceramics doped with Y 2O 3 and CeO 2 was prepared using traditional processing method. The fine grain PSZ ceramics( d c10 μm) sintered at low temperature(1550 ℃) was obtained by means of composition ...Mg PSZ ceramics doped with Y 2O 3 and CeO 2 was prepared using traditional processing method. The fine grain PSZ ceramics( d c10 μm) sintered at low temperature(1550 ℃) was obtained by means of composition design. The effects of co stabilization of Y 2O 3, CeO 2 and annealing at 1100 ℃ on material composition, microstructure and mechanical properties were studied. The results show that Y 2O 3 and CeO 2 during annealing at 1100 ℃ can inhibit subeutectoid decomposition reaction effectively, and optimize nucleation and growth of t ZrO 2 precipitates in c ZrO 2 matrix phase. The materials show transgranular and intergranular fracture characteristics, and exhibit better mechanical properties owing to the cooperative effect of stress induced transformation toughening and microcrack toughening.展开更多
The structure and properties of Mg-doped SrBi4Ti4O15（SBT） were dicussed. Mg substitution into SBT had two possibilities states with the dopant amount variety. Mg cation substituted mostly into Sr^2＋ and the amount ...The structure and properties of Mg-doped SrBi4Ti4O15（SBT） were dicussed. Mg substitution into SBT had two possibilities states with the dopant amount variety. Mg cation substituted mostly into Sr^2＋ and the amount proportion was 68.11%.Mg ion will substitute into Ti ion site in perovskite layer when the doping amount increases. Polarization increases sharply when x=0.1 and then decreases becauses of the domain pinning. The Curie temperature of Mg-doped SBT is about 300 ℃ and there is a broad diffuse phase transition near Tc with a flat peak near the Ta of SBT.展开更多
The chemical vapor deposition(CVD)growth method is applicable to produce high-yield single-crystalline ZnO nanobelts.The Mg-doped ZnO nanobelts with a smooth surface have been successfully synthesized.The morphology,m...The chemical vapor deposition(CVD)growth method is applicable to produce high-yield single-crystalline ZnO nanobelts.The Mg-doped ZnO nanobelts with a smooth surface have been successfully synthesized.The morphology,microstructure and optical properties of the ZnO nanobelts were analyzed by X-ray diffraction(XRD),scanning electron microscope(SEM),transmission electron microscope(TEM),selective area electron diffraction(SAED),energy dispersive X-ray spectroscopy(EDS)and photoluminescence(PL)spectroscopy.Results reveal that the ZnO nanobelts possess good crystalline quality.The special formation mechanism of crystal growth is discussed,emphasizing the effect of polar orientation on the nucleation and growth of the ZnO nanobelts.展开更多
Lithium iron phosphate （LiFePO4） doped with magnesium was hydrothermally synthesized from commercial LiOH, FeSO4, H3PO4 and MgSO4 with glucose as carbon precursor in aqueous solution. The samples were characterized ...Lithium iron phosphate （LiFePO4） doped with magnesium was hydrothermally synthesized from commercial LiOH, FeSO4, H3PO4 and MgSO4 with glucose as carbon precursor in aqueous solution. The samples were characterized by X-ray powder diffraction, scanning electron microscopy and constant charge-discharge cycling. The results show that the synthesized powders have been in situ coated with carbon precursor produced from caramel reaction of glucose. At ambient temperature （28±2℃）, the electrochemical performances of LiFePO4 prepared exhibit the high discharge capacity of 135 mAh g^-1 at 5C and good capacity retention of 98% over 90 cycles. The excellent electrochemical performances should be correlated with the intimate contact between carbon and LiFePO4 primary and secondary particles, resulting from the in situ formation of carbon precursor/carbon, leading to the increase in conductivity of LiFePO4.展开更多
基金financially supported by the National Natural Science Foundation of China(No.51904250)the China Postdoctoral Science Foundation(No.2021M692254)+2 种基金the Sichuan Science and Technology Program(No.2022YFG0098)the Fundamental Research Funds for the Central Universities(Nos.2021CDSN-02,2022SCU12002,2022CDZG-17,2022CDSN-08,2022CDZG-9)the Hohhot Science and Technology Program(No.2023-Jie Bang Gua Shuai-Gao-3)。
文摘Mn-rich LiFe_(1-x)Mn_(x)PO_(4)(x>0.5),which combines the high operation voltage of LiMnPO_(4)with excellent rate performa nce of LiFePO4,is hindered by its sluggish kinetic properties.Herein,thermodynamic equilibrium analysis of Mn^(2+)-Fe^(2+)-Mg^(2+)-C_(2)O_(4)^(2-)-H_(2)O system is used to guide the design and preparation of insitu Mg-doped(Fe_(0.4)Mn_(0.6))_(1-x)Mg_(x)C_(2)O_(4)intermediate,which is then employed as an innovative precursor to synthesize high-performance Mg-doped LiFe_(0.4)Mn_(0.6)PO_(4).It indicates that the metal ions with a high precipitation efficiency and the stoichiometric precursors with uniform element distribution can be achieved under the optimized thermodynamic conditions.Meanwhile,accelerated Li+diffusivity and reduced charge transfer resistance originating from Mg doping are verified by various kinetic characterizations.Benefiting from the contributions of inherited homogeneous element distribution,small particle size,uniform carbon layer coating,enhanced Li+migration ability and structural stability induced by Mg doping,the Li(Fe_(0.4)Mn_(0.6))_(0.97)Mg_(0.03)PO_(4)/C exhibits splendid electrochemical performance.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2017YFB0403100 and 2017YFB0403101)the National Natural Science Foundation of China(Grant Nos.61704149,61674076,and 61605071)+7 种基金the Natural Science Foundation of Jiangsu Province,China(Grant Nos.BY2013077,BK20141320,and BE2015111)the Project of Science and Technology Development Program in Shandong Province,China(Grant Nos.2013YD02054 and 2013YD02008)the Project of Shandong Provincial Higher Educational Science and Technology Program,China(Grant No.J13LN08)the Collaborative Innovation Center of Solid State Lighting and Energy-saving Electronics,Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)the Six-Talent Peaks Project of Jiangsu Province,China(Grant No.XYDXX-081)the Open Fund of the State Key Laboratory on Integrated Optoelectronics,China(Grant No.IOSKL2017KF03)the Project of Autonomous Innovation and Achievement Transformation Program in Zaozhuang City,China(Grant No.2017GH3)the Overseas Study Program Funded by Shandong Provincial Government,China,the Laboratory Open Fund from Jiangsu Key Laboratory of Photoelectric Information Functional Materials,China,and the Doctoral Foundation Project of Zaozhuang University,China.
文摘The Mg acceptor activation mechanism and hole transport characteristics in AlGaN alloy with Mg doping concentration(~ 1020 cm-3) grown by metal–organic chemical vapor deposition(MOCVD) are systematically studied through optical and electrical properties. Emission lines of shallow oxygen donors and(VⅢ complex)1- as well as VN3+ and neutral Mg acceptors are observed, which indicate that self-compensation is occurred in Mg-doped AlGaN at highly doping levels. The fitting of the temperature-dependent Hall effect data shows that the acceptor activation energy values in Mgdoped AlxGa1-xN(x = 0.23, 0.35) are 172 meV and 242 meV, and the hole concentrations at room temperature are 1.2×1018 cm-3 and 3.3× 1017 cm-3, respectively. Therefore, it is believed that there exists the combined effect of the Coulomb potentials of the dopants and screening of the Coulomb potentials by a high hole concentration. Moreover, due to the high ionized acceptors’ concentration and compensation ratio, the impurity conduction becomes more prominent and the valence band mobility drops sharply at low temperature.
基金Funded by the Scientific Research Fund of Hunan Education Department(10C0294)
文摘The layered LiNi0.6Co0.2-xMn0.2MgxO2 （x=0.00,0.03,0.05,0.07） cathode materials were prepared by a co-precipitation method.The properties of the Mg-doped LiNi0.6Co0.2Mn0.2O2 were investigated by X-ray diffraction （XRD）,scanning electron microscopy （SEM）,and electrochemical measurements.XRD studies showed that the Mg-doped LiNi0.6Co0.2Mn0.2O2 had the same layered structure as the undoped LiNi0.6Co0.2Mn0.2O2.The SEM images exhibited that the particle size of Mg-doped LiNi0.6Co0.2Mn0.2O2 was finer than that of the undoped LiNi0.6Co0.2 Mn0.2O2 and that the smallest particle size is only about 1μm.The Mg-doped LiNi0.6Co0.2Mn0.2O2 samples were investigated on the Li extraction/insertion performances through charge/discharge,cyclic voltammogram （CV）,and electrochemical impedance spectra（EIS）.The optimal doping content of Mg was that x= 0.03 in the LiNi0.6Co0.2-xMn0.2MgxO2 samples to achieve high discharge capacity and good cyclic stability.The electrode reaction reversibility and electronic conductivity was enhanced,and the charge transfer resistance was decreased through Mg-doping.The improved electrochemical performances of the Mg-doped LiNi0.6Co0.2Mn0.2O2 cathode materials are attributed to the addition of Mg 2＋ ion by stabilizing the layer structure.
基金Funded by the National Natural Science Foundation of China(No.51072162).
文摘The microstructure and performance of Li4Ti5O12 doped by Mg prepared by hydrothermal method and solid phase method were investigated. Lithium dihydrate, magnesium acetate and tetrabutyl titanate were used as the main raw materials. This study reveals that Mg^2+ has influences on the spherical structure, crystal development of Li4Ti5O12 and the electrochemical performances. The hollow spherical structure is composed of nano-sheet structure and the nano-sheet structure can be affected by the Mg^2+ content. For Li4-xMgxTi5 O12, the sheet structure can be refined with the increment of Mg^2+ content when x value is 0-0.1 and coarsen with the increment of Mg^2+ content when x value is 0.1-0.2. The hollow spherical Li4Ti5O12 powders prepared by hydrothermal method have better performance. The optimal Mgdoped amount of hydrothermal method is 0.1. At 0.1 C, the first discharge capacity of Li3.9Mg0.1Ti5O12 prepared through hydrothermal method at 0.1 C and 10 cycles is 182 and 178 mA hg^-1, respectively.
基金Project supported by the SINANO-SONY Joint Program(Grant No.Y1AAQ11001)the National Natural Science Foundation of China(Grant No.61274134)+1 种基金the USCB Start-up Program(Grant No.06105033)the International Cooperation Projects of Suzhou City,China(Grant No.SH201215)
文摘We report a GaInP/GaAs tandem solar cell with a novel GaAs tunnel junction（TJ） with using tellurium（Te） and magnesium（Mg） as n- and p-type dopants via dual-filament low temperature effusion cells grown by molecular beam epitaxy（MBE） at low temperature. The test Te/Mg-doped GaAs TJ shows a peak current density of 21 A/cm2. The tandem solar cell by the Te/Mg TJ shows a short-circuit current density of 12 m A/cm2, but a low open-circuit voltage range of1.4 V^1.71 V under AM1.5 illumination. The secondary ion mass spectroscopy（SIMS） analysis reveals that the Te doping is unexpectedly high and its doping profile extends to the Mg doping region, thus possibly resulting in a less abrupt junction with no tunneling carriers effectively. Furthermore, the tunneling interface shifts from the intended Ga As n＋＋/p＋＋junction to the AlGaInP/GaAs junction with a higher bandgap AlGaInP tunneling layers, thereby reducing the tunneling peak. The Te concentration of ~ 2.5 × 1020 in GaAs could cause a lattice strain of 10-3 in magnitude and thus a surface roughening,which also negatively influences the subsequent growth of the top subcell and the GaAs contacting layers. The doping features of Te and Mg are discussed to understand the photovoltaic response of the studied tandem cell.
文摘Mg PSZ ceramics doped with Y 2O 3 and CeO 2 was prepared using traditional processing method. The fine grain PSZ ceramics( d c10 μm) sintered at low temperature(1550 ℃) was obtained by means of composition design. The effects of co stabilization of Y 2O 3, CeO 2 and annealing at 1100 ℃ on material composition, microstructure and mechanical properties were studied. The results show that Y 2O 3 and CeO 2 during annealing at 1100 ℃ can inhibit subeutectoid decomposition reaction effectively, and optimize nucleation and growth of t ZrO 2 precipitates in c ZrO 2 matrix phase. The materials show transgranular and intergranular fracture characteristics, and exhibit better mechanical properties owing to the cooperative effect of stress induced transformation toughening and microcrack toughening.
基金Funded by the Natural Science Foundation of China (No. 50472016, 50502027)the main project of the Ministry of Education (MOE) of China and the Chenguang Science Plan of Wuhan (No. 200750731268)
文摘The structure and properties of Mg-doped SrBi4Ti4O15（SBT） were dicussed. Mg substitution into SBT had two possibilities states with the dopant amount variety. Mg cation substituted mostly into Sr^2＋ and the amount proportion was 68.11%.Mg ion will substitute into Ti ion site in perovskite layer when the doping amount increases. Polarization increases sharply when x=0.1 and then decreases becauses of the domain pinning. The Curie temperature of Mg-doped SBT is about 300 ℃ and there is a broad diffuse phase transition near Tc with a flat peak near the Ta of SBT.
基金National Natural Science Foundation of China(90301002,90201025)
文摘The chemical vapor deposition(CVD)growth method is applicable to produce high-yield single-crystalline ZnO nanobelts.The Mg-doped ZnO nanobelts with a smooth surface have been successfully synthesized.The morphology,microstructure and optical properties of the ZnO nanobelts were analyzed by X-ray diffraction(XRD),scanning electron microscope(SEM),transmission electron microscope(TEM),selective area electron diffraction(SAED),energy dispersive X-ray spectroscopy(EDS)and photoluminescence(PL)spectroscopy.Results reveal that the ZnO nanobelts possess good crystalline quality.The special formation mechanism of crystal growth is discussed,emphasizing the effect of polar orientation on the nucleation and growth of the ZnO nanobelts.
文摘Lithium iron phosphate （LiFePO4） doped with magnesium was hydrothermally synthesized from commercial LiOH, FeSO4, H3PO4 and MgSO4 with glucose as carbon precursor in aqueous solution. The samples were characterized by X-ray powder diffraction, scanning electron microscopy and constant charge-discharge cycling. The results show that the synthesized powders have been in situ coated with carbon precursor produced from caramel reaction of glucose. At ambient temperature （28±2℃）, the electrochemical performances of LiFePO4 prepared exhibit the high discharge capacity of 135 mAh g^-1 at 5C and good capacity retention of 98% over 90 cycles. The excellent electrochemical performances should be correlated with the intimate contact between carbon and LiFePO4 primary and secondary particles, resulting from the in situ formation of carbon precursor/carbon, leading to the increase in conductivity of LiFePO4.
