As an interconnector of solid oxide fuel cell, La 1-x Ca x CrO 3( x =0 0～0 5) were prepared by sol gel method. The crystal structures of La 1-x Ca x CrO 3 at room temperature are the or...As an interconnector of solid oxide fuel cell, La 1-x Ca x CrO 3( x =0 0～0 5) were prepared by sol gel method. The crystal structures of La 1-x Ca x CrO 3 at room temperature are the orthorhombic perovskite GdFeO 3 type. XPS analysis indicates that chrome ions are in different valence state. The introduction of Ca 2+ into the lattice induces the oxidation of Cr 3+ to Cr 6+ . With x increasing, the amount of Cr 6+ increases. The present of the more Cr 6+ is one of the important factors that effect electric conductivity of La 1-x Ca x CrO 3.展开更多
Samples of manganese oxides La（1-x）2/3Ca1/3MnO3（x 〈 0.10） with Lavacancy were prepared by standard solid-state reaction method. All the samples are single phase, with orthorhombic symmetry （Pnma ）, analyzed by ...Samples of manganese oxides La（1-x）2/3Ca1/3MnO3（x 〈 0.10） with Lavacancy were prepared by standard solid-state reaction method. All the samples are single phase, with orthorhombic symmetry （Pnma ）, analyzed by XRD and with Rietveld Refinement. The effect of different La-site vacancies concentration on electronic transport of La（1-x）2/3Ca1/3MnO3 was investigated. The insulator-metal transition temperature （about 267 K） nearly remains unchanged with the increase of vacancy concentration, which indicates that small La-vacancy does not destroy the double exchange interaction. But the electronic resistance increases and MR value decreases with La-vacancy content x 〉 0.04. The maximum of the MR value （8 T） is about 220% at transition temperature （TMI）.展开更多
Pr0.6-x NdxCa0.4 FeO3-δ （ x = 0.0, 0.2, 0.3, 0.4, 0.5, 0.6） were synthesized using Pechini method. A number of studies were conducted concerning composition, specific area, crystalline structure and microstructure ...Pr0.6-x NdxCa0.4 FeO3-δ （ x = 0.0, 0.2, 0.3, 0.4, 0.5, 0.6） were synthesized using Pechini method. A number of studies were conducted concerning composition, specific area, crystalline structure and microstructure of the samples by means of FT-IR, BET, XRD TG-DTA and SEM. The results show that all the samples with different doping amounts of Pr^3＋ and Nd^3＋ on A-site are fine dispersed, and mean particle size less than 100 nm. The powders have good sinterability, and the relative density is 95% after sintered at 1200 ℃ for 2 h. It is found that all specimens are entirely single phase solid solutions with orthorhombic perovskite structure, the stable perovskitetype phase is formed completely after calcination at 900 ℃.展开更多
The influences of W doping at Mn site on the charge order and spin order were studied by measuring M-T curves, M-H curves and ESR spectra of La0.3Ca0.7Mn1?xWxO3 (x = 0.00, 0.04, 0.08, 0.12, 0.15) system. The results s...The influences of W doping at Mn site on the charge order and spin order were studied by measuring M-T curves, M-H curves and ESR spectra of La0.3Ca0.7Mn1?xWxO3 (x = 0.00, 0.04, 0.08, 0.12, 0.15) system. The results showed that: When 0.00≤ x≤0.08, the system exhibits charge ordering (CO) phase, and its spin order experiences the change of paramagnetism (PM)-charge ordering (CO)-antiferro- magnetism (AFM) with decreasing temperature; when x≥0.12, the charge ordering (CO) phase melts, part of charge ordering (CO)phase remains in the paramagnetism (PM)background, the spin order of the system is mainly paramagnetism (PM), and ferromagnetic (FM) clusters appear at low tem- perature.展开更多
文摘As an interconnector of solid oxide fuel cell, La 1-x Ca x CrO 3( x =0 0～0 5) were prepared by sol gel method. The crystal structures of La 1-x Ca x CrO 3 at room temperature are the orthorhombic perovskite GdFeO 3 type. XPS analysis indicates that chrome ions are in different valence state. The introduction of Ca 2+ into the lattice induces the oxidation of Cr 3+ to Cr 6+ . With x increasing, the amount of Cr 6+ increases. The present of the more Cr 6+ is one of the important factors that effect electric conductivity of La 1-x Ca x CrO 3.
文摘Samples of manganese oxides La（1-x）2/3Ca1/3MnO3（x 〈 0.10） with Lavacancy were prepared by standard solid-state reaction method. All the samples are single phase, with orthorhombic symmetry （Pnma ）, analyzed by XRD and with Rietveld Refinement. The effect of different La-site vacancies concentration on electronic transport of La（1-x）2/3Ca1/3MnO3 was investigated. The insulator-metal transition temperature （about 267 K） nearly remains unchanged with the increase of vacancy concentration, which indicates that small La-vacancy does not destroy the double exchange interaction. But the electronic resistance increases and MR value decreases with La-vacancy content x 〉 0.04. The maximum of the MR value （8 T） is about 220% at transition temperature （TMI）.
文摘Pr0.6-x NdxCa0.4 FeO3-δ （ x = 0.0, 0.2, 0.3, 0.4, 0.5, 0.6） were synthesized using Pechini method. A number of studies were conducted concerning composition, specific area, crystalline structure and microstructure of the samples by means of FT-IR, BET, XRD TG-DTA and SEM. The results show that all the samples with different doping amounts of Pr^3＋ and Nd^3＋ on A-site are fine dispersed, and mean particle size less than 100 nm. The powders have good sinterability, and the relative density is 95% after sintered at 1200 ℃ for 2 h. It is found that all specimens are entirely single phase solid solutions with orthorhombic perovskite structure, the stable perovskitetype phase is formed completely after calcination at 900 ℃.
基金supported by the National Natural Science Foundation of China(Grant No.19934003)the State Key Project of Fundamental Research of China(No.001CB610604)
文摘The influences of W doping at Mn site on the charge order and spin order were studied by measuring M-T curves, M-H curves and ESR spectra of La0.3Ca0.7Mn1?xWxO3 (x = 0.00, 0.04, 0.08, 0.12, 0.15) system. The results showed that: When 0.00≤ x≤0.08, the system exhibits charge ordering (CO) phase, and its spin order experiences the change of paramagnetism (PM)-charge ordering (CO)-antiferro- magnetism (AFM) with decreasing temperature; when x≥0.12, the charge ordering (CO) phase melts, part of charge ordering (CO)phase remains in the paramagnetism (PM)background, the spin order of the system is mainly paramagnetism (PM), and ferromagnetic (FM) clusters appear at low tem- perature.
