Two series of perovskite-type oxides with composition (La_(1-x))Sr_xFeO_3(x≤0.8)and La_(1-x)Sr_xFe_(1-y)Co_yO_3(x=0.2; y=0.2, 0.4)powder productions were synthesized by EDTA complexing sol-gel method. The products we...Two series of perovskite-type oxides with composition (La_(1-x))Sr_xFeO_3(x≤0.8)and La_(1-x)Sr_xFe_(1-y)Co_yO_3(x=0.2; y=0.2, 0.4)powder productions were synthesized by EDTA complexing sol-gel method. The products were characterized by XRD, TEM, SEM, BET method(N_2 adsorption)and laser granularity analysis for different synthesis conditions to obtain the optimum conditions for the preparation process. Single-phased, uniform perovskite-type oxides with small particle size were obtained by EDTA sol-gel process with high stability and repeatability, and the process temperature is much lower than that of solid state reaction method.展开更多
Li 2+ x RE x Si 1- x O 3(RE=Pr, Nd, Sm, Gd; x =0～0 15) samples were prepared by the sol gel method. DTA TG, XRD, TEM and A C impedance techniques were used to investigate the structure, sha...Li 2+ x RE x Si 1- x O 3(RE=Pr, Nd, Sm, Gd; x =0～0 15) samples were prepared by the sol gel method. DTA TG, XRD, TEM and A C impedance techniques were used to investigate the structure, shape, and ionic conductivity of these samples. The results show that the range of solid solution formation is in 0< x ≤0 09, in which the conductivity of these samples raises with the increasing amount of RE 2O 3 (RE=Pr, Nd, Sm, Gd) added, and the diameter of the powders is about 100 nm. Compared with the conventional solid state reaction, the sol gel method needs low temperature and presents high ionic conductivity.展开更多
Bulk polycrystalline samples of La0.60Sr0.4MnO3 and La0.60Sr0.25-yNa0.15ΔyMnO3 with 0.00≤y≤0.15 (“Δ” representing cation vacancy) were successfully synthesized using the sol-gel method. The structural, magnetic,...Bulk polycrystalline samples of La0.60Sr0.4MnO3 and La0.60Sr0.25-yNa0.15ΔyMnO3 with 0.00≤y≤0.15 (“Δ” representing cation vacancy) were successfully synthesized using the sol-gel method. The structural, magnetic, and electrical properties of the polycrystalline of the samples were investigated. The results of X-ray powder diffraction patterns show that these compounds crystallize in a distorted rhombohedral structure with the space group R3C. The measurement shows that, with vacancy content y increasing, the unit cell volume V of samples increases, furthermore, the Curie temperature TC decreases. The temperature dependence of resistivity shows that all samples undergo a metal-semiconductor transition accompanying a ferromagnetic to paramagnetic transition with the increase of temperature. Under an applied filed of 1.8 T, a maximum room temperature magnetoresistance (MR) of 20% is obtained at 293 K for the compound La0.60Sr0.1Na0.15Δ0.15MnO3. The MR peak value of La0.60Sr0.1Na0.15Δ0.15MnO3 increases 2 times more than that of La0.60Sr0.40MnO3 (MRP=6.4%, TMR=373 K), and the MR peak is shifted from 373 K to room temperature.展开更多
Due to the remarkable magnetoresistance (MR) effect on perovskite-type manganite, magnetoelectronics and spintronics have become attractive subjects of experimental and theoretical investigations for the application p...Due to the remarkable magnetoresistance (MR) effect on perovskite-type manganite, magnetoelectronics and spintronics have become attractive subjects of experimental and theoretical investigations for the application purpose. (La0.9Nd0.1)2/3Ca1/3Mn1-xFexO3(x=0, x=0.05) were prepared successfully by sol-gel method. The structure, magnetic properties, and transport properties of the compounds were investigated. The magnetoresistance effect depends on the composition and the temperature. XRD patterns show that the compound is a single phase polycrystal with pseudocubic structure. A large negative isotropic magnetoresistance effect in the samples were observed at low temperature region. The maximum MR of the samples was 77% and 97%, respectively. It was most likely due to the scattering or the tunneling transport of spin-polarized carriers in lattice under strong magnetic field.展开更多
The catalytic performance of perovskite composite oxide catalyst La0.9 K0.1 CoO3 coated on catalyst supports by traditional solid state reaction method and sol-gel method were investigated by a series of experiments....The catalytic performance of perovskite composite oxide catalyst La0.9 K0.1 CoO3 coated on catalyst supports by traditional solid state reaction method and sol-gel method were investigated by a series of experiments. The restdt shows that the catalytic performance of the La0.9 K0.1 CoO3 perovskite composite oxide catalyst synthesized by sol-gel method is superior to that synthesized by solid state reaction method, having lower ignition temperature of the diesel soot particulates, lower start temperature of NOx treatment, and lower concentration of byproduct CO.展开更多
A series of ternary perovskite type oxides LaNi1-xCuxO3(x = 0.2,0.4,0.6,0.8,and 1.0) were synthesized via the sol-gel method in propionic acid.Partial substitution of Ni by Cu showed higher activities and selectivitie...A series of ternary perovskite type oxides LaNi1-xCuxO3(x = 0.2,0.4,0.6,0.8,and 1.0) were synthesized via the sol-gel method in propionic acid.Partial substitution of Ni by Cu showed higher activities and selectivities towards syngas products.LaNi0.8Cu0.2O3 was the most active toward the CH4 and CO2 conversions,and was selective for syngas products.Temperature-programmed reduction results showed that the addition of Cu facilitates the reduction of Ni3+ to Ni0,which is the main reason for the higher performance of this catalyst.展开更多
Nanometer perovskite LaMnO 3+λ, La 0.6Ce 0.4MnO 3+λ and La 0.6Sr 0.4MnO 3+λ were prepared by citric acid-aid ed sol-gel method. The effects of Ce, Sr on the structure and properties of nan ome...Nanometer perovskite LaMnO 3+λ, La 0.6Ce 0.4MnO 3+λ and La 0.6Sr 0.4MnO 3+λ were prepared by citric acid-aid ed sol-gel method. The effects of Ce, Sr on the structure and properties of nan ometer perovskite were studied through DT-TGA, XRD, TEM and BET analyses. The r esults show that, by sol-gel method, LaMnO 3+λ, La 0.6Ce 0. 4MnO 3+λ and La 0.6Sr 0.4MnO 3+λ were made with average particle size of about 60, 100 and 30 nm, respectively. After partially substituting Sr on La positions in LaMnO 3+λ, it is found that Sr is l ocated at the perovskite lattice so as to reduce the formation temperature of th e perovskite. As a result, the perovskite has a smaller particle size and larger specific surface area. On the contrary, it is difficult for Ce to enter the per ovskite lattice. Ce exists mostly in the form of CeO 2 as partially substitutin g La in LaMnO 3+λ. The formation temperature of the perovskite increas es, and the catalyst containing CeO 2 presents a larger particle size and less specific surface area.展开更多
Two methods for preparing La0.9K0.1CoO3 perovskite composite oxides.traditional solid state reaction method and sol-gel method.were compared.The characteristics of the powders,such as purity.particle diameter,BET surf...Two methods for preparing La0.9K0.1CoO3 perovskite composite oxides.traditional solid state reaction method and sol-gel method.were compared.The characteristics of the powders,such as purity.particle diameter,BET surface area,pore diameter,were inrestigated by using TG-DTA,XRD,SEM and BET methods.The experimental results shou that La0.9K0.1CoO3 perorskite composite oxide can be obtained by using the two methods.The purity of La0.9K0.1CoO3 powders can be increased by raising the calcining temperature while the particle diameter increased and BET surface area decreased.At the same calcining temperature,the properties of the La0.9K0.1CoO3 powders synthesized by the sol-gel method are superior to those synthesized by the solid state reaction method.such as purer phase,smaller particle diameter,which can be used as a satisfactory catalyst in diesel waste gas cleaning.展开更多
文摘Two series of perovskite-type oxides with composition (La_(1-x))Sr_xFeO_3(x≤0.8)and La_(1-x)Sr_xFe_(1-y)Co_yO_3(x=0.2; y=0.2, 0.4)powder productions were synthesized by EDTA complexing sol-gel method. The products were characterized by XRD, TEM, SEM, BET method(N_2 adsorption)and laser granularity analysis for different synthesis conditions to obtain the optimum conditions for the preparation process. Single-phased, uniform perovskite-type oxides with small particle size were obtained by EDTA sol-gel process with high stability and repeatability, and the process temperature is much lower than that of solid state reaction method.
文摘Li 2+ x RE x Si 1- x O 3(RE=Pr, Nd, Sm, Gd; x =0～0 15) samples were prepared by the sol gel method. DTA TG, XRD, TEM and A C impedance techniques were used to investigate the structure, shape, and ionic conductivity of these samples. The results show that the range of solid solution formation is in 0< x ≤0 09, in which the conductivity of these samples raises with the increasing amount of RE 2O 3 (RE=Pr, Nd, Sm, Gd) added, and the diameter of the powders is about 100 nm. Compared with the conventional solid state reaction, the sol gel method needs low temperature and presents high ionic conductivity.
基金This work was financially supported by the National Natural Science Foundation of China (No.NSF-10074016), the Natural Science Foundation of Hebei Province (No.E2006000168) and Science Foundation of Hebei Education Department (No.2005358).
文摘Bulk polycrystalline samples of La0.60Sr0.4MnO3 and La0.60Sr0.25-yNa0.15ΔyMnO3 with 0.00≤y≤0.15 (“Δ” representing cation vacancy) were successfully synthesized using the sol-gel method. The structural, magnetic, and electrical properties of the polycrystalline of the samples were investigated. The results of X-ray powder diffraction patterns show that these compounds crystallize in a distorted rhombohedral structure with the space group R3C. The measurement shows that, with vacancy content y increasing, the unit cell volume V of samples increases, furthermore, the Curie temperature TC decreases. The temperature dependence of resistivity shows that all samples undergo a metal-semiconductor transition accompanying a ferromagnetic to paramagnetic transition with the increase of temperature. Under an applied filed of 1.8 T, a maximum room temperature magnetoresistance (MR) of 20% is obtained at 293 K for the compound La0.60Sr0.1Na0.15Δ0.15MnO3. The MR peak value of La0.60Sr0.1Na0.15Δ0.15MnO3 increases 2 times more than that of La0.60Sr0.40MnO3 (MRP=6.4%, TMR=373 K), and the MR peak is shifted from 373 K to room temperature.
文摘Due to the remarkable magnetoresistance (MR) effect on perovskite-type manganite, magnetoelectronics and spintronics have become attractive subjects of experimental and theoretical investigations for the application purpose. (La0.9Nd0.1)2/3Ca1/3Mn1-xFexO3(x=0, x=0.05) were prepared successfully by sol-gel method. The structure, magnetic properties, and transport properties of the compounds were investigated. The magnetoresistance effect depends on the composition and the temperature. XRD patterns show that the compound is a single phase polycrystal with pseudocubic structure. A large negative isotropic magnetoresistance effect in the samples were observed at low temperature region. The maximum MR of the samples was 77% and 97%, respectively. It was most likely due to the scattering or the tunneling transport of spin-polarized carriers in lattice under strong magnetic field.
基金Funded by National Natural Science Foundation of China(No2001AA643020)
文摘The catalytic performance of perovskite composite oxide catalyst La0.9 K0.1 CoO3 coated on catalyst supports by traditional solid state reaction method and sol-gel method were investigated by a series of experiments. The restdt shows that the catalytic performance of the La0.9 K0.1 CoO3 perovskite composite oxide catalyst synthesized by sol-gel method is superior to that synthesized by solid state reaction method, having lower ignition temperature of the diesel soot particulates, lower start temperature of NOx treatment, and lower concentration of byproduct CO.
文摘A series of ternary perovskite type oxides LaNi1-xCuxO3(x = 0.2,0.4,0.6,0.8,and 1.0) were synthesized via the sol-gel method in propionic acid.Partial substitution of Ni by Cu showed higher activities and selectivities towards syngas products.LaNi0.8Cu0.2O3 was the most active toward the CH4 and CO2 conversions,and was selective for syngas products.Temperature-programmed reduction results showed that the addition of Cu facilitates the reduction of Ni3+ to Ni0,which is the main reason for the higher performance of this catalyst.
文摘Nanometer perovskite LaMnO 3+λ, La 0.6Ce 0.4MnO 3+λ and La 0.6Sr 0.4MnO 3+λ were prepared by citric acid-aid ed sol-gel method. The effects of Ce, Sr on the structure and properties of nan ometer perovskite were studied through DT-TGA, XRD, TEM and BET analyses. The r esults show that, by sol-gel method, LaMnO 3+λ, La 0.6Ce 0. 4MnO 3+λ and La 0.6Sr 0.4MnO 3+λ were made with average particle size of about 60, 100 and 30 nm, respectively. After partially substituting Sr on La positions in LaMnO 3+λ, it is found that Sr is l ocated at the perovskite lattice so as to reduce the formation temperature of th e perovskite. As a result, the perovskite has a smaller particle size and larger specific surface area. On the contrary, it is difficult for Ce to enter the per ovskite lattice. Ce exists mostly in the form of CeO 2 as partially substitutin g La in LaMnO 3+λ. The formation temperature of the perovskite increas es, and the catalyst containing CeO 2 presents a larger particle size and less specific surface area.
文摘Two methods for preparing La0.9K0.1CoO3 perovskite composite oxides.traditional solid state reaction method and sol-gel method.were compared.The characteristics of the powders,such as purity.particle diameter,BET surface area,pore diameter,were inrestigated by using TG-DTA,XRD,SEM and BET methods.The experimental results shou that La0.9K0.1CoO3 perorskite composite oxide can be obtained by using the two methods.The purity of La0.9K0.1CoO3 powders can be increased by raising the calcining temperature while the particle diameter increased and BET surface area decreased.At the same calcining temperature,the properties of the La0.9K0.1CoO3 powders synthesized by the sol-gel method are superior to those synthesized by the solid state reaction method.such as purer phase,smaller particle diameter,which can be used as a satisfactory catalyst in diesel waste gas cleaning.
