Cr-doped Li3V2（PO4）3 cathode materials Li3V2-xCr（PO4）3 were prepared by a carbothermal reduction（CTR） process. The properties of the Cr-doped Li3V2（PO4）3 were investigated by X-ray diffraction （XRD）, scannin...Cr-doped Li3V2（PO4）3 cathode materials Li3V2-xCr（PO4）3 were prepared by a carbothermal reduction（CTR） process. The properties of the Cr-doped Li3V2（PO4）3 were investigated by X-ray diffraction （XRD）, scanning electron microscopic （SEM）, and electrochemical measurements Results show that the Cr-doped Li3V2（PO4）3 has the same monoclinic structure as the undoped Li3V2（PO4）3, and the particle size of Cr-doped Li3V2（PO4）3 is smaller than that of the undoped Li3V2（PO4）3 and the smallest particle size is only about 1 1μm. The Cr-doped Li3V2（PO4）3 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 Cr was that x=0.04 in the Li3V2-xCrx（PO4）3 samples to achieve high discharge capacity and good cyclic stability. The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through the Cr-doping. The improved electrochemical performances of the Cr-doped Li3V2（PO4）3 cathode materials are attributed to the addition of Cr^3＋ ion by stabilizing the monoclinic structure.展开更多
Novel organic-inorganic composite photocatalyst offers new opportunities in the practical applications of photocatalysis. Novel visible light-induced Cr-doped Sr Ti O3–carbon nitride intercalation compound(CNIC) comp...Novel organic-inorganic composite photocatalyst offers new opportunities in the practical applications of photocatalysis. Novel visible light-induced Cr-doped Sr Ti O3–carbon nitride intercalation compound(CNIC) composite photocatalysts were synthesized. The composite photocatalyst was characterized by X-ray diffraction(XRD), field-emission scanning electron microscopy(FESEM), high-resolution transmission electron microscopy(HRTEM), Fourier transform infrared(FT-IR) spectroscopy, UV-vis diffuse reflection spectroscopy, photoluminescence(PL) spectroscopy, and BET surface area analyzer. The photocatalytic oxidation ability of the novel composite photocatalyst was evaluated using methyl orange(MO) as a target pollutant. The photocatalysts exhibited a significantly enhanced photocatalytic performance in degrading MO. For maximizing the photodegradation activity of the composite photocatalysts, the optimal CNIC content was determined. The improved photocatalytic activity of the as-prepared Cr-doped Sr Ti O3–CNIC composite photocatalyst may be attributed to the enhancement of photo-generated electron–hole separations at the interface.展开更多
Novel visible light-induced Cr-doped Sr Ti O3-g-C3N4 composite photocatalysts were synthesized by introducing polymeric g-C3N4. The composite photocatalyst was characterized by X-ray diffraction（XRD）, high-resolutio...Novel visible light-induced Cr-doped Sr Ti O3-g-C3N4 composite photocatalysts were synthesized by introducing polymeric g-C3N4. The composite photocatalyst was characterized by X-ray diffraction（XRD）, high-resolution transmission electron microscopy（HRTEM）, Fourier transform infrared（FT-IR） spectroscopy, UV-vis diffuse reflection spectroscopy, photoluminescence（PL） spectroscopy and BET surface area measurements. The photocatalytic oxidation ability of the novel composite photocatalyst was evaluated using methyl orange（MO） as a target pollutant. The photocatalysts exhibited a significantly enhanced photocatalytic performance in degrading MO. The optimal g-C3N4 content for the photodegradation activity of the composite photocatalysts was determined. The as-prepared composite photocatalyst exhibits an improved photocatalytic activity due to enhancement of photo-generated electron-hole separation at the interface.展开更多
Large crystal growth of Cr-doped h-YMnO3has been investigated by using a high pressure optical floatingzone method. The size of the grown crystals is typically 60–70 mm in length and 4–5 mm in diameter. The structur...Large crystal growth of Cr-doped h-YMnO3has been investigated by using a high pressure optical floatingzone method. The size of the grown crystals is typically 60–70 mm in length and 4–5 mm in diameter. The structure of the grown crystals is analyzed by powder X-ray diffraction and scanning electron microscopy.The defects in the as-grown crystals, including low-angle grain boundary and inclusions are studied. An off-stoichiometric phenomenon is found with a slight Cr deficiency in different parts. The relationship between defects and growth conditions during crystal growth is also discussed. The magnetic properties show spin-glass phase features with weak ferromagnetic behavior below 30 K.展开更多
Cr-doped Sr TiO_(3)/Ti-dopedα-Fe_(2)O_(3) heterojunction has been constructed by an ingenious way,i.e.using segregation titanium oxide on the surface of the Ti-dopedα-Fe_(2)O_(3) electrode to in situ prepare Cr-dope...Cr-doped Sr TiO_(3)/Ti-dopedα-Fe_(2)O_(3) heterojunction has been constructed by an ingenious way,i.e.using segregation titanium oxide on the surface of the Ti-dopedα-Fe_(2)O_(3) electrode to in situ prepare Cr-doped SrTiO_(3).After construction of the heterojunction,the photocurrent onset potential for water oxidation on a Ti4+dopedα-Fe_(2)O_(3) cathodically shifts by about 100 mV.Moreover,the cathodic shift of the onset potential can be preserved well even after a long time running.The results indicate the effectiveness and credibility of the fabricated heterojunction.In order to make clear the reason for the onset potential shift,the asprepared Ti-dopedα-Fe_(2)O_(3) and Cr-doped SrTiO_(3)/Ti-dopedα-Fe_(2)O_(3) samples were investigated by X-ray photoelectron spectroscopy,electrochemical impedance spectroscopy,X-ray diffraction spectroscopy,etc.Based on the experimental evidences,it is proposed that cathodic shift of the onset potential is mainly due to the enhanced charge separation at the photoanode surface.This strategy can offer a reference to construct heterojunction on other films especially for those with surface segregation.展开更多
This paper deals with the effect of Cr content on photocatalytic activity of TiO2 thin films deposited on quartz and intrinsic silicon substrates by using the RF magnetron co-sputtering process. Some physical investig...This paper deals with the effect of Cr content on photocatalytic activity of TiO2 thin films deposited on quartz and intrinsic silicon substrates by using the RF magnetron co-sputtering process. Some physical investigations on such sputtered films were made by means of X-ray Diffraction (XRD), atomic force microscopy (AFM), Raman spectroscopy as well as UV-Vis-IR absorption techniques. The heat treatment under oxygen atmosphere at 550°C reveals that the crystalline structure of TiO2: Cr depends on Cr content. Anatase-to-rutile phase transformation occurs at a Cr content of about 7%. On the other hand, the band gap energy value of annealed TiO2: Cr films varies in terms of Cr doping and a transition around 7% of Cr is accrued. The photocatalytic activity of undoped and doped TiO2 films was evaluated by photo-degrading of the amido black under UV light irradiation. Modification of the chemical structure of titanium dioxide by Cr doping allows moving the photocatalytic activity of titanium dioxide towards visible light. The results indicate that films doped with 2% Cr exhibit the highest UV and visible light photocatalytic activity.展开更多
The first-principles calculations were performed to investigate the electronic structure, magnetic and dielectric properties of Cr-doped Fe_3C, in comparison to those of pure Fe_3C and Cr_3C. The obtained results show...The first-principles calculations were performed to investigate the electronic structure, magnetic and dielectric properties of Cr-doped Fe_3C, in comparison to those of pure Fe_3C and Cr_3C. The obtained results show that the thermodynamic stability of Crdoped Fe_3C becomes weaker in terms of the larger formation enthalpy, on the contrary, the metallicity and covalency are found to strengthen to some extent. The magnetic moments of Fe_3C, Fe_(11)CrC_4(g), and Fe_(11)CrC_4(s) are respectively 21.36 μB/cell, 16.92 μB/cell, and 17.62 μB/cell, and in Fe_(11)CrC4(g) and Fe_(11)CrC_4(s), the Fe of Wyckoff positions of 8d and 4c is substituted by Cr. The local magnetic moment of Cr at 8d site is larger than that at 4c site in the doped structure, which is opposite to that of Fe. In low frequency band, the permittivity follows the ranking of Fe_(11)Cr C_4(s)>Cr_3C>Fe_(11)Cr C_4(g)>Fe_3C. Once exceeding a certain frequency, the sequence will be broken. Besides the electron transition, the polarization of atoms also makes a contribution to the dielectric properties.展开更多
A series of Cr^(3+)-substituted Na_(1+x)Ti_(2−x)Cr_(x)P_(3)O_(12)(x=0.1,0.2,0.3,0.4,0.5,molar fraction)solid electrolytes were prepared by the solid-phase reaction method.The effects of Cr^(3+)ions on the phase compos...A series of Cr^(3+)-substituted Na_(1+x)Ti_(2−x)Cr_(x)P_(3)O_(12)(x=0.1,0.2,0.3,0.4,0.5,molar fraction)solid electrolytes were prepared by the solid-phase reaction method.The effects of Cr^(3+)ions on the phase composition,microstructure,and electrochemical ion conductivity of Na-based conductors were studied using X-ray powder diffraction,field emission scanning electron microscopy,and AC impedance measurement.The results show that the main crystal phase of NaTi_(2)(PO_(4))_(3) is formed in the solid electrolytes.The substitution of Ti4+sites by 15 at.%Cr^(3+)ions contributes to the enhancement of electrical conductivity,which is attributed to the combined effect of suppressing the formation of impurity phases,broadening ion channels,and improving the bonding degree of grains.Na_(1.3)Ti_(1.7)Cr_(0.3)P_(3)O_(12) electrolyte can obtain the best ionic conductivity of 6.13×10^(−6)S/cm at room temperature,which is 8 times that of the undoped NaTi_(2)(PO_(4))_(3) electrolyte.展开更多
Memristor-based architectures hold great potential for future computing systems.However,the reliance on monotonous electrical input to regulate resistance limits the possibilities for high-density storage and multifun...Memristor-based architectures hold great potential for future computing systems.However,the reliance on monotonous electrical input to regulate resistance limits the possibilities for high-density storage and multifunctional integration.In this work,we report a multi-functional memristor based on optical and electrical modulation,utilizing double perovskite oxide materials.La_(2)CoMn_(1-x)Cr_(x)O_(6)(x=0,0.15,0.25,0.35)films were fabricated on a LaNiO_(3)/SiO_(2)/Si conductive heterojunction via the sol-gel method.Among the different Cr doping concentrations,x=0.25(25%Cr)was found to be the optimal condition,enhancing both surface quality and resistive switching(RS)performance in the La_(2)CoMn_(1-x)Cr_(x)O_(6)-based films.For the first time,ten distinct resistance states were achieved in an Au/La_(2)CoMn_(0.75)Cr_(0.25)O_(6)(Cr-LCMO-25)/LaNiO_(3)/SiO_(2)/Si device,driven by varying light intensity(650 nm).These states remained stable for 12,000 s and over 450 cycles,demonstrating excellent multilevel RS memory performance in the Cr-LCMO-25-based device.The RS behavior followed the oxygen vacancy(OV)-controlled space charge-limited current model.Cr doping increased the OV concentration,which in turn enhanced the RS behavior.Additionally,photoinduced carriers at the Au/Cr-LCMO-25 interface modulated the Schottky-like barrier,further influencing the multilevel RS behavior.Importantly,complex logic operations,including AND,OR,NOT,and XNOR,were successfully performed using both electrical and optical inputs.This study offers a promising approach to increase memory density,simplify logic circuits,and create lead-free double perovskite-based multifunctional memristors.展开更多
Sodium-ion batteries are considered as promising alternatives to lithium-ion batteries,owing to their low cost and abundant raw materials.Among the several candidate materials for the anode,spinel-type Li_(4)Ti_(5)O_(...Sodium-ion batteries are considered as promising alternatives to lithium-ion batteries,owing to their low cost and abundant raw materials.Among the several candidate materials for the anode,spinel-type Li_(4)Ti_(5)O_(12)has potential owing to its superior safety originating from an appropriate operating voltage and the reversible Na^(+)intercalation properties.However,a low diffusion coefficient for Na^(+)and the insulating nature of LTO remains challenging for practical sodium-ion battery systems.Herein,we present a strategy for integrating physical and chemical approaches to achieve superior electrochemical properties in LTO.We demonstrate that carefully controlling the amount of Cr doping is crucial to enhance the electrochemical properties of nanostructured LTO.Optimized Cr doped LTO shows a superior reversible capacity of 110 m Ah g^(-1) after 400 cycles at 1 C,with a three-fold higher capacity(75 m Ah g^(-1))at 10 C compared with undoped LTO material.This suggests that appropriately Cr doped nanostructured LTO is a promising anode material for sodium-ion batteries.展开更多
Efficient and robust noble-metal-free bifunctional electrocatalysts for overall water splitting(OWS)is of great importance to realize the large-scale hydrogen production.Herein,we report the growth of undoped and Cr-d...Efficient and robust noble-metal-free bifunctional electrocatalysts for overall water splitting(OWS)is of great importance to realize the large-scale hydrogen production.Herein,we report the growth of undoped and Cr-doped NiCo2O4(Cr-NiCo2O4)nanoneedles(NNs)on nickel foam(NF)as bifunctional electrocatalysts for both hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).We demonstrate that Cr-doping significantly improves activity for HER and OER by increasing the conductivity of NNs and allowing more active sites on NNs electrochemically accessible.When amorphous FeOOH is electrodeposited on the surface of Cr-NiCo2O4 NNs,the resulting FeOOH/Cr-NiCo2O4/NF exhibits itself as an excellent bifunctional catalyst for OWS.In the two-electrode cell where FeOOH/Cr-NiCo2O4/NF is used both as cathode and anode for OWS,a cell voltage of only 1.65 V is required to achieve an electrolysis current density of 100 mA·cm^−2.In addition,the catalyst shows a very high stability for OWS,the two-electrode cell can operate at a consist current density of 20 mA·cm^−2 for 10 h OWS with the cell voltage being stable at ca.1.60 V.These results demonstrate that FeOOH/Cr-NiCo2O4/NF possesses an OWS performance superior to most of transition-metal based bifunctional electrocatalysts working in alkaline medium.The excellent bifunctional activity and stability of FeOOH/Cr-NiCo2O4/NF are attributed to the following reasons:(i)The NN structure provides a large specific surface area;(ii)the high conductivity of Cr-NiCo2O4 enables more active centers on the far-end part of NNs to be electrochemically reached;(iii)the deposition of FeOOH supplies additional active sites for OWS.展开更多
Zn1-xCrxO （x = 0.00, 0.01, 0.03, 0.05, 0.07, and 0.09） nanoparticles were synthesized, by an auto-com- bustion method. Structural, optical, and magnetic characteristics of Cr-doped ZnO samples calcined at 600 ℃ hav...Zn1-xCrxO （x = 0.00, 0.01, 0.03, 0.05, 0.07, and 0.09） nanoparticles were synthesized, by an auto-com- bustion method. Structural, optical, and magnetic characteristics of Cr-doped ZnO samples calcined at 600 ℃ have been analyzed by using X-ray diffraction （XRD）, field emission scanning electron microscope （FESEM）, UV-Vis spectroscopy and vibrating sample magnetometer （VSM）. The XRD data confirmed the hexagonal wurtzite structure of pure and Cr-doped ZnO nanoparticles. The calculated values of grain size using Scherrer＇s formula are in the range of 30.7-9.2 nm. The morphology of nanopowders has been observed by FESEM, and EDS results con- firmed a systematic increase of Cr content in the samples and clearly indicate with no impurity element. The band gaps, computed by UV-Vis spectroscopy, are in the range of 2.83-2.35 eV for different doping concentrations. By analyzing VSM data, significantly enhanced room temperature ferromagnetism is identified in Cr-doped ZnO samples. The value of magnetization is a 12 times increased of the value reported by Daun et al. （2010）. Room temperature ferromagnetism of the nanoparticles is of vital prominence for spintronics applications.展开更多
LiNi0.33Mn0.33-xCo0.33CrxO2 (x=0, 0.01, 0.025, 0.05) materials were synthesized by Cr3+ substitute of Mn4+ to enhance their electrochemical properties. The structure and electrochemical properties were characterized b...LiNi0.33Mn0.33-xCo0.33CrxO2 (x=0, 0.01, 0.025, 0.05) materials were synthesized by Cr3+ substitute of Mn4+ to enhance their electrochemical properties. The structure and electrochemical properties were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and charge/dis charge tests. The materials maintained the α-NaFeO2 type layered structure and the discharge capacities were also increase by doping appropriate amount of Cr3+. The sample with x= 0.025 exhibited the highest discharge capability of 181.6 mAh g?1 and the best cycle performance. EIS measurement showed that the Cr-doped electrode had the lower resistance impedance increase during cycling. The chemical diffusion coefficient of Li+ ion (DLi) was measured by potentiostatic intermittent titration technique (PITT). The result showed that DLi in Cr-doped electrode was faster than that of the un-doped one.展开更多
基金Funded by the Guangxi Natural Science Foundation(No. 0832259)the National Basic Research Program of China (No. 2007CB613607)
文摘Cr-doped Li3V2（PO4）3 cathode materials Li3V2-xCr（PO4）3 were prepared by a carbothermal reduction（CTR） process. The properties of the Cr-doped Li3V2（PO4）3 were investigated by X-ray diffraction （XRD）, scanning electron microscopic （SEM）, and electrochemical measurements Results show that the Cr-doped Li3V2（PO4）3 has the same monoclinic structure as the undoped Li3V2（PO4）3, and the particle size of Cr-doped Li3V2（PO4）3 is smaller than that of the undoped Li3V2（PO4）3 and the smallest particle size is only about 1 1μm. The Cr-doped Li3V2（PO4）3 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 Cr was that x=0.04 in the Li3V2-xCrx（PO4）3 samples to achieve high discharge capacity and good cyclic stability. The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through the Cr-doping. The improved electrochemical performances of the Cr-doped Li3V2（PO4）3 cathode materials are attributed to the addition of Cr^3＋ ion by stabilizing the monoclinic structure.
基金Project(51208102)supported by the National Natural Science Foundation of China
文摘Novel organic-inorganic composite photocatalyst offers new opportunities in the practical applications of photocatalysis. Novel visible light-induced Cr-doped Sr Ti O3–carbon nitride intercalation compound(CNIC) composite photocatalysts were synthesized. The composite photocatalyst was characterized by X-ray diffraction(XRD), field-emission scanning electron microscopy(FESEM), high-resolution transmission electron microscopy(HRTEM), Fourier transform infrared(FT-IR) spectroscopy, UV-vis diffuse reflection spectroscopy, photoluminescence(PL) spectroscopy, and BET surface area analyzer. The photocatalytic oxidation ability of the novel composite photocatalyst was evaluated using methyl orange(MO) as a target pollutant. The photocatalysts exhibited a significantly enhanced photocatalytic performance in degrading MO. For maximizing the photodegradation activity of the composite photocatalysts, the optimal CNIC content was determined. The improved photocatalytic activity of the as-prepared Cr-doped Sr Ti O3–CNIC composite photocatalyst may be attributed to the enhancement of photo-generated electron–hole separations at the interface.
基金Funded by the National Natural Science Foundation of China(No.51208102)
文摘Novel visible light-induced Cr-doped Sr Ti O3-g-C3N4 composite photocatalysts were synthesized by introducing polymeric g-C3N4. The composite photocatalyst was characterized by X-ray diffraction（XRD）, high-resolution transmission electron microscopy（HRTEM）, Fourier transform infrared（FT-IR） spectroscopy, UV-vis diffuse reflection spectroscopy, photoluminescence（PL） spectroscopy and BET surface area measurements. The photocatalytic oxidation ability of the novel composite photocatalyst was evaluated using methyl orange（MO） as a target pollutant. The photocatalysts exhibited a significantly enhanced photocatalytic performance in degrading MO. The optimal g-C3N4 content for the photodegradation activity of the composite photocatalysts was determined. The as-prepared composite photocatalyst exhibits an improved photocatalytic activity due to enhancement of photo-generated electron-hole separation at the interface.
基金financial support of the National Natural Science Foundation of China (Nos. 51471135 and 51301133)the National Key Research and Development Program (No. 2016YFB1100101)Shaanxi International Cooperation Program
文摘Large crystal growth of Cr-doped h-YMnO3has been investigated by using a high pressure optical floatingzone method. The size of the grown crystals is typically 60–70 mm in length and 4–5 mm in diameter. The structure of the grown crystals is analyzed by powder X-ray diffraction and scanning electron microscopy.The defects in the as-grown crystals, including low-angle grain boundary and inclusions are studied. An off-stoichiometric phenomenon is found with a slight Cr deficiency in different parts. The relationship between defects and growth conditions during crystal growth is also discussed. The magnetic properties show spin-glass phase features with weak ferromagnetic behavior below 30 K.
基金financially supported by the National Natural Science Foundation of China(Nos.61474064 and 61504063)the Natural Science Foundation of Jiangsu Province(No.BK20150836)+2 种基金the Jiangsu National Synergetic Innovation Center for Advanced Materials(SICAM)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD,No.YX030003)the Synergistic Innovation Center for Organic Electronics and Information Displays。
文摘Cr-doped Sr TiO_(3)/Ti-dopedα-Fe_(2)O_(3) heterojunction has been constructed by an ingenious way,i.e.using segregation titanium oxide on the surface of the Ti-dopedα-Fe_(2)O_(3) electrode to in situ prepare Cr-doped SrTiO_(3).After construction of the heterojunction,the photocurrent onset potential for water oxidation on a Ti4+dopedα-Fe_(2)O_(3) cathodically shifts by about 100 mV.Moreover,the cathodic shift of the onset potential can be preserved well even after a long time running.The results indicate the effectiveness and credibility of the fabricated heterojunction.In order to make clear the reason for the onset potential shift,the asprepared Ti-dopedα-Fe_(2)O_(3) and Cr-doped SrTiO_(3)/Ti-dopedα-Fe_(2)O_(3) samples were investigated by X-ray photoelectron spectroscopy,electrochemical impedance spectroscopy,X-ray diffraction spectroscopy,etc.Based on the experimental evidences,it is proposed that cathodic shift of the onset potential is mainly due to the enhanced charge separation at the photoanode surface.This strategy can offer a reference to construct heterojunction on other films especially for those with surface segregation.
基金This work was financed by the Ministry of Higher Education,Scientific Research and Technology of Tunisia and Institut National de la Recherche Scientifique Canada,INRS-Énergie,Matériauxet Télécommunications(INRS-EMT).
文摘This paper deals with the effect of Cr content on photocatalytic activity of TiO2 thin films deposited on quartz and intrinsic silicon substrates by using the RF magnetron co-sputtering process. Some physical investigations on such sputtered films were made by means of X-ray Diffraction (XRD), atomic force microscopy (AFM), Raman spectroscopy as well as UV-Vis-IR absorption techniques. The heat treatment under oxygen atmosphere at 550°C reveals that the crystalline structure of TiO2: Cr depends on Cr content. Anatase-to-rutile phase transformation occurs at a Cr content of about 7%. On the other hand, the band gap energy value of annealed TiO2: Cr films varies in terms of Cr doping and a transition around 7% of Cr is accrued. The photocatalytic activity of undoped and doped TiO2 films was evaluated by photo-degrading of the amido black under UV light irradiation. Modification of the chemical structure of titanium dioxide by Cr doping allows moving the photocatalytic activity of titanium dioxide towards visible light. The results indicate that films doped with 2% Cr exhibit the highest UV and visible light photocatalytic activity.
基金Project(51174252)supported by the Joint Funds of the National Natural Science Foundation of China
文摘The first-principles calculations were performed to investigate the electronic structure, magnetic and dielectric properties of Cr-doped Fe_3C, in comparison to those of pure Fe_3C and Cr_3C. The obtained results show that the thermodynamic stability of Crdoped Fe_3C becomes weaker in terms of the larger formation enthalpy, on the contrary, the metallicity and covalency are found to strengthen to some extent. The magnetic moments of Fe_3C, Fe_(11)CrC_4(g), and Fe_(11)CrC_4(s) are respectively 21.36 μB/cell, 16.92 μB/cell, and 17.62 μB/cell, and in Fe_(11)CrC4(g) and Fe_(11)CrC_4(s), the Fe of Wyckoff positions of 8d and 4c is substituted by Cr. The local magnetic moment of Cr at 8d site is larger than that at 4c site in the doped structure, which is opposite to that of Fe. In low frequency band, the permittivity follows the ranking of Fe_(11)Cr C_4(s)>Cr_3C>Fe_(11)Cr C_4(g)>Fe_3C. Once exceeding a certain frequency, the sequence will be broken. Besides the electron transition, the polarization of atoms also makes a contribution to the dielectric properties.
基金supported by the National Natural Science Foundation of China(No.51972344)the Natural Science Foundation of Hunan Province,China(No.2018JJ3646).
文摘A series of Cr^(3+)-substituted Na_(1+x)Ti_(2−x)Cr_(x)P_(3)O_(12)(x=0.1,0.2,0.3,0.4,0.5,molar fraction)solid electrolytes were prepared by the solid-phase reaction method.The effects of Cr^(3+)ions on the phase composition,microstructure,and electrochemical ion conductivity of Na-based conductors were studied using X-ray powder diffraction,field emission scanning electron microscopy,and AC impedance measurement.The results show that the main crystal phase of NaTi_(2)(PO_(4))_(3) is formed in the solid electrolytes.The substitution of Ti4+sites by 15 at.%Cr^(3+)ions contributes to the enhancement of electrical conductivity,which is attributed to the combined effect of suppressing the formation of impurity phases,broadening ion channels,and improving the bonding degree of grains.Na_(1.3)Ti_(1.7)Cr_(0.3)P_(3)O_(12) electrolyte can obtain the best ionic conductivity of 6.13×10^(−6)S/cm at room temperature,which is 8 times that of the undoped NaTi_(2)(PO_(4))_(3) electrolyte.
基金supported by the National Natural Science Foundation of China(Nos.12104106,12464012,12464028,12164005,12074382,11804062,and 11474285)the Natural Science Foundation of Guangxi Zhuang Autonomous Region(No.2021GXNSFAA220044).
文摘Memristor-based architectures hold great potential for future computing systems.However,the reliance on monotonous electrical input to regulate resistance limits the possibilities for high-density storage and multifunctional integration.In this work,we report a multi-functional memristor based on optical and electrical modulation,utilizing double perovskite oxide materials.La_(2)CoMn_(1-x)Cr_(x)O_(6)(x=0,0.15,0.25,0.35)films were fabricated on a LaNiO_(3)/SiO_(2)/Si conductive heterojunction via the sol-gel method.Among the different Cr doping concentrations,x=0.25(25%Cr)was found to be the optimal condition,enhancing both surface quality and resistive switching(RS)performance in the La_(2)CoMn_(1-x)Cr_(x)O_(6)-based films.For the first time,ten distinct resistance states were achieved in an Au/La_(2)CoMn_(0.75)Cr_(0.25)O_(6)(Cr-LCMO-25)/LaNiO_(3)/SiO_(2)/Si device,driven by varying light intensity(650 nm).These states remained stable for 12,000 s and over 450 cycles,demonstrating excellent multilevel RS memory performance in the Cr-LCMO-25-based device.The RS behavior followed the oxygen vacancy(OV)-controlled space charge-limited current model.Cr doping increased the OV concentration,which in turn enhanced the RS behavior.Additionally,photoinduced carriers at the Au/Cr-LCMO-25 interface modulated the Schottky-like barrier,further influencing the multilevel RS behavior.Importantly,complex logic operations,including AND,OR,NOT,and XNOR,were successfully performed using both electrical and optical inputs.This study offers a promising approach to increase memory density,simplify logic circuits,and create lead-free double perovskite-based multifunctional memristors.
基金supported by the Korea Institute of Science and Technology(KIST)Institutional Program(Project No.2E30212)the National Research Foundation of Korea(NRF)(NRF-2020M3H4A1A0308297811)。
文摘Sodium-ion batteries are considered as promising alternatives to lithium-ion batteries,owing to their low cost and abundant raw materials.Among the several candidate materials for the anode,spinel-type Li_(4)Ti_(5)O_(12)has potential owing to its superior safety originating from an appropriate operating voltage and the reversible Na^(+)intercalation properties.However,a low diffusion coefficient for Na^(+)and the insulating nature of LTO remains challenging for practical sodium-ion battery systems.Herein,we present a strategy for integrating physical and chemical approaches to achieve superior electrochemical properties in LTO.We demonstrate that carefully controlling the amount of Cr doping is crucial to enhance the electrochemical properties of nanostructured LTO.Optimized Cr doped LTO shows a superior reversible capacity of 110 m Ah g^(-1) after 400 cycles at 1 C,with a three-fold higher capacity(75 m Ah g^(-1))at 10 C compared with undoped LTO material.This suggests that appropriately Cr doped nanostructured LTO is a promising anode material for sodium-ion batteries.
基金We gratefully acknowledge the financial support of this work by the National Natural Science Foundation of China(Nos.51872015 and 51672017).
文摘Efficient and robust noble-metal-free bifunctional electrocatalysts for overall water splitting(OWS)is of great importance to realize the large-scale hydrogen production.Herein,we report the growth of undoped and Cr-doped NiCo2O4(Cr-NiCo2O4)nanoneedles(NNs)on nickel foam(NF)as bifunctional electrocatalysts for both hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).We demonstrate that Cr-doping significantly improves activity for HER and OER by increasing the conductivity of NNs and allowing more active sites on NNs electrochemically accessible.When amorphous FeOOH is electrodeposited on the surface of Cr-NiCo2O4 NNs,the resulting FeOOH/Cr-NiCo2O4/NF exhibits itself as an excellent bifunctional catalyst for OWS.In the two-electrode cell where FeOOH/Cr-NiCo2O4/NF is used both as cathode and anode for OWS,a cell voltage of only 1.65 V is required to achieve an electrolysis current density of 100 mA·cm^−2.In addition,the catalyst shows a very high stability for OWS,the two-electrode cell can operate at a consist current density of 20 mA·cm^−2 for 10 h OWS with the cell voltage being stable at ca.1.60 V.These results demonstrate that FeOOH/Cr-NiCo2O4/NF possesses an OWS performance superior to most of transition-metal based bifunctional electrocatalysts working in alkaline medium.The excellent bifunctional activity and stability of FeOOH/Cr-NiCo2O4/NF are attributed to the following reasons:(i)The NN structure provides a large specific surface area;(ii)the high conductivity of Cr-NiCo2O4 enables more active centers on the far-end part of NNs to be electrochemically reached;(iii)the deposition of FeOOH supplies additional active sites for OWS.
基金Project supported by the Office of Research,Innovation,and Commercialization(ORIC),MUST Mirpur(AJK)
文摘Zn1-xCrxO （x = 0.00, 0.01, 0.03, 0.05, 0.07, and 0.09） nanoparticles were synthesized, by an auto-com- bustion method. Structural, optical, and magnetic characteristics of Cr-doped ZnO samples calcined at 600 ℃ have been analyzed by using X-ray diffraction （XRD）, field emission scanning electron microscope （FESEM）, UV-Vis spectroscopy and vibrating sample magnetometer （VSM）. The XRD data confirmed the hexagonal wurtzite structure of pure and Cr-doped ZnO nanoparticles. The calculated values of grain size using Scherrer＇s formula are in the range of 30.7-9.2 nm. The morphology of nanopowders has been observed by FESEM, and EDS results con- firmed a systematic increase of Cr content in the samples and clearly indicate with no impurity element. The band gaps, computed by UV-Vis spectroscopy, are in the range of 2.83-2.35 eV for different doping concentrations. By analyzing VSM data, significantly enhanced room temperature ferromagnetism is identified in Cr-doped ZnO samples. The value of magnetization is a 12 times increased of the value reported by Daun et al. （2010）. Room temperature ferromagnetism of the nanoparticles is of vital prominence for spintronics applications.
基金supported by the National Hi-Tech Research and Develop-ment Program of China ("863" Project) (Grant No. 2009AA11A106)the National Basic Research Program of China ("973" Project) (Grant Nos. 2001CB211800, 2009CB220100) BIT Basic Research Fund (Grant No. 20070542004)
文摘LiNi0.33Mn0.33-xCo0.33CrxO2 (x=0, 0.01, 0.025, 0.05) materials were synthesized by Cr3+ substitute of Mn4+ to enhance their electrochemical properties. The structure and electrochemical properties were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and charge/dis charge tests. The materials maintained the α-NaFeO2 type layered structure and the discharge capacities were also increase by doping appropriate amount of Cr3+. The sample with x= 0.025 exhibited the highest discharge capability of 181.6 mAh g?1 and the best cycle performance. EIS measurement showed that the Cr-doped electrode had the lower resistance impedance increase during cycling. The chemical diffusion coefficient of Li+ ion (DLi) was measured by potentiostatic intermittent titration technique (PITT). The result showed that DLi in Cr-doped electrode was faster than that of the un-doped one.
