Phase pure powders of SrCeO3 and Sr2Ce O4 have been synthesized by calcination at 1000℃for 14 h via solid state ceramic route.Ceramics/pellets of these samples have been obtained by sintering at 1200℃for 12 h.The Ri...Phase pure powders of SrCeO3 and Sr2Ce O4 have been synthesized by calcination at 1000℃for 14 h via solid state ceramic route.Ceramics/pellets of these samples have been obtained by sintering at 1200℃for 12 h.The Rietveld refinement of X-ray diffraction(XRD)pattern of sintered powders confirmed orthorhombic structure of both the samples with space group Pnma and Pbam for SrCeO3 and Sr2CeO4,respectively.Scanning electron microscopic(SEM)studies indicated that both the compounds have dense microstructure,but morphology and size of the grains are different.The impedance spectroscopy technique has been employed to study the relaxation phenomenon.DC conductivity of the samples has been measured in the temperature range of 200–600℃to understand the conduction mechanism.The activation energy for relaxation(Erelax)and DC conduction(Econd)are found to be the same for both the compounds.Based on the numerical value of activation energies,relaxation and conduction mechanism in both the samples are attributed to migration of doubly ionized oxygen vacancies(Vo··).Photoluminescence technique has been employed to confirm the existence of oxygen vacancies.These studies have indicated that migration of oxygen vacancies in Sr2CeO4 is occurring mainly along a and c direction,i.e.,via perovskite cells.Further,the present work has clearly indicated that besides optical properties,electrical properties of Sr2CeO4 are also interesting and can be utilized for various applications such as oxide ion conduction electrolyte in solid oxide fuel cells(SOFCs).展开更多
Zr-substituted,Tm-doped SrCeO3（SrCe0.95-xZrxTm0.05O3-δ,0≤x≤0.40）were synthesized via citrate complexing method,and the membranes of SrCe0.95-xZrxTm0.05O3-δwere prepared by pressing followed by sintering. X-ray d...Zr-substituted,Tm-doped SrCeO3（SrCe0.95-xZrxTm0.05O3-δ,0≤x≤0.40）were synthesized via citrate complexing method,and the membranes of SrCe0.95-xZrxTm0.05O3-δwere prepared by pressing followed by sintering. X-ray diffraction（XRD）was used to characterize the phase structure of sintered membrane.The microstructure of the sintered membranes was studied by scanning electron microscopy（SEM）.Protonic and electronic conductivities were measured under different circumstance.Hydrogen permeation through the SrCe0.75Zr0.20Tm0.05O3-δmembranes was carried out using gas permeation setup.Hydrogen permeation fluxes（ 2H J）of the SrCe0.75Zr0.20Tm0.05O3-δ membrane reach up to 0.042 ml·min^ -1 ·cm^-2 at H 2 partial pressure of 0.4×10 ^5 Pa at 900°C.The hydrogen permea- tion fluxes（ 2H J）obtained in this paper are slightly lower than that of SrCe0.95Tm0.05O3-δon the same orders,and Zr doping can increase chemical stability of the SrCe0.75Zr0.20Tm0.05O3-δmembranes.展开更多
A molten salt method was developed for the synthesis of ACeO3（A=Sr, Ba） with perovskite structure at 750 ℃（SrCeO3） and 850 ℃（BaCeO3） in the eutectic NaCl-KCl. The synthetic temperature was much lower than that...A molten salt method was developed for the synthesis of ACeO3（A=Sr, Ba） with perovskite structure at 750 ℃（SrCeO3） and 850 ℃（BaCeO3） in the eutectic NaCl-KCl. The synthetic temperature was much lower than that of the conventional method（generally〉1000 ℃）. The structure and morphology of the product were characterized by means of X-ray diffraction（XRD）, field emission scanning electron microscopy（FESEM） and transmission electron microscopy（TEM）. The results show that the synthesized octahedral SrCeO3 crystallizes in the orthorhombic system with the unit cell parameters of a=0.85855 nm, b=0.61523 nm, c=0.60059 nm, and the synthesized cuboid BaCeO3 crystallizes in the cubic system with the unit cell parameter of a=0.43962 nm. The result of X-ray photoelectron spectroscopy（XPS） analysis indicates that both Ce4＋ and Ce3＋ exist in the two structures, and the Ce4＋/Ce3＋ peak area ratios for SrCeO3 and BaCeO3 are 1.93 and 2.12, respectively. Meanwhile, the adsorbed/lattice oxygen ratios（1.87 for SrCeO3 and 3.04 for BaCeO3） indicate the existence of a lot of oxygen vacancies in the structures of SrCeO3 and BaCeO3, which indicates a far-reaching significance to study the corresponding physicochemistry performance.展开更多
基金the Ministry of Human Resource and Development (MHRD)the Government of India and co-ordinator for the financial support in terms of Senior Research Fellowship (SRF)
文摘Phase pure powders of SrCeO3 and Sr2Ce O4 have been synthesized by calcination at 1000℃for 14 h via solid state ceramic route.Ceramics/pellets of these samples have been obtained by sintering at 1200℃for 12 h.The Rietveld refinement of X-ray diffraction(XRD)pattern of sintered powders confirmed orthorhombic structure of both the samples with space group Pnma and Pbam for SrCeO3 and Sr2CeO4,respectively.Scanning electron microscopic(SEM)studies indicated that both the compounds have dense microstructure,but morphology and size of the grains are different.The impedance spectroscopy technique has been employed to study the relaxation phenomenon.DC conductivity of the samples has been measured in the temperature range of 200–600℃to understand the conduction mechanism.The activation energy for relaxation(Erelax)and DC conduction(Econd)are found to be the same for both the compounds.Based on the numerical value of activation energies,relaxation and conduction mechanism in both the samples are attributed to migration of doubly ionized oxygen vacancies(Vo··).Photoluminescence technique has been employed to confirm the existence of oxygen vacancies.These studies have indicated that migration of oxygen vacancies in Sr2CeO4 is occurring mainly along a and c direction,i.e.,via perovskite cells.Further,the present work has clearly indicated that besides optical properties,electrical properties of Sr2CeO4 are also interesting and can be utilized for various applications such as oxide ion conduction electrolyte in solid oxide fuel cells(SOFCs).
基金Supported by the Joint Funds of NSFC-Guangdong （U0834004）, the National Natural Science Foundation of China （20976057） and the Natural Science Foundation of Guangdong Province （06025657）.
文摘Zr-substituted,Tm-doped SrCeO3（SrCe0.95-xZrxTm0.05O3-δ,0≤x≤0.40）were synthesized via citrate complexing method,and the membranes of SrCe0.95-xZrxTm0.05O3-δwere prepared by pressing followed by sintering. X-ray diffraction（XRD）was used to characterize the phase structure of sintered membrane.The microstructure of the sintered membranes was studied by scanning electron microscopy（SEM）.Protonic and electronic conductivities were measured under different circumstance.Hydrogen permeation through the SrCe0.75Zr0.20Tm0.05O3-δmembranes was carried out using gas permeation setup.Hydrogen permeation fluxes（ 2H J）of the SrCe0.75Zr0.20Tm0.05O3-δ membrane reach up to 0.042 ml·min^ -1 ·cm^-2 at H 2 partial pressure of 0.4×10 ^5 Pa at 900°C.The hydrogen permea- tion fluxes（ 2H J）obtained in this paper are slightly lower than that of SrCe0.95Tm0.05O3-δon the same orders,and Zr doping can increase chemical stability of the SrCe0.75Zr0.20Tm0.05O3-δmembranes.
基金the National Natural Science Foundation of China（Nos.51472025, 21271021）.
文摘A molten salt method was developed for the synthesis of ACeO3（A=Sr, Ba） with perovskite structure at 750 ℃（SrCeO3） and 850 ℃（BaCeO3） in the eutectic NaCl-KCl. The synthetic temperature was much lower than that of the conventional method（generally〉1000 ℃）. The structure and morphology of the product were characterized by means of X-ray diffraction（XRD）, field emission scanning electron microscopy（FESEM） and transmission electron microscopy（TEM）. The results show that the synthesized octahedral SrCeO3 crystallizes in the orthorhombic system with the unit cell parameters of a=0.85855 nm, b=0.61523 nm, c=0.60059 nm, and the synthesized cuboid BaCeO3 crystallizes in the cubic system with the unit cell parameter of a=0.43962 nm. The result of X-ray photoelectron spectroscopy（XPS） analysis indicates that both Ce4＋ and Ce3＋ exist in the two structures, and the Ce4＋/Ce3＋ peak area ratios for SrCeO3 and BaCeO3 are 1.93 and 2.12, respectively. Meanwhile, the adsorbed/lattice oxygen ratios（1.87 for SrCeO3 and 3.04 for BaCeO3） indicate the existence of a lot of oxygen vacancies in the structures of SrCeO3 and BaCeO3, which indicates a far-reaching significance to study the corresponding physicochemistry performance.
