A series of compounds La2Mo2-xSnxO9-6 (x=0-0.3) have been synthesized by solid-state reaction technique. Materials have been characterized by XRD, SEM, DSC and impedance study. In the temperature regime 520℃-590 ℃...A series of compounds La2Mo2-xSnxO9-6 (x=0-0.3) have been synthesized by solid-state reaction technique. Materials have been characterized by XRD, SEM, DSC and impedance study. In the temperature regime 520℃-590 ℃, the specimens with x〈0.05 have the conductivity higher than La2Mo2O9. Conductivity of Sn-doped compound decreases consistently with increasing Sn-doping, compared to the undoped compound both below and above phase transition, barring the specimens with x〈 0.05, where conductivity values remains almost same as that of undoped specimen in high temperature region. In the intermediate temperature regime (520℃-590℃), the conductivity of doped compounds increases for x〈0.05 as compared to parent compound. Also, there is no indication of phase stabilization with Sn-doping in this compound even with the highest doping level, x=0.3. Electric modulus analysis suggests that thermally activated oxygen ion hopping mechanism is responsible for the conduction in Sn-doped compound.展开更多
A cost-efFective technique, including nanocrystalline powder preparation using a modified Pechini method and a two-step low-temperature sintering route, was developed for the synthesis of high performance La2Mo2O9- ba...A cost-efFective technique, including nanocrystalline powder preparation using a modified Pechini method and a two-step low-temperature sintering route, was developed for the synthesis of high performance La2Mo2O9- based oxide-ion conductors. The optimum parameters of the compaction pressure, the first step and 'the second step sintering temperatures for the synthesis of fine grained, high density and uniform La2Mo2O9- based oxide-ion conductors were determined by a series of sintering experiments. High density and uniform sintered La2Mo2O9 samples with average grain size from 0.8 to 5 μm and La1.96K0.04Mo2O8.96 sample with average grain size as small as 500 nm were synthesized by using this cost-efFective method. The impedance measurement results show that the as-fabricated La2Mo2O9-based ceramics possess much higher ionic conductivity than that obtained by solid state reaction method. It is found that in the range of 0.8-5μm the grain size of dense La2Mo2O9 samples prepared from the nanocrystalline powders has little influence on their conductivities.展开更多
A new oxide ion conductor, La3GaMo2O12, with a bulk conductivity of 2.7× 10^- 2 S·cm ^-1 at 800 ℃ in air atmosphere was prepared by the traditional solid-state reaction. The room temperature X-ray diffracti...A new oxide ion conductor, La3GaMo2O12, with a bulk conductivity of 2.7× 10^- 2 S·cm ^-1 at 800 ℃ in air atmosphere was prepared by the traditional solid-state reaction. The room temperature X-ray diffraction data could be indexed on a monoclinic cell with lattice parameters of a=0.5602(2) nm, b=0.3224(1) nm, c= 1.5741(1) nm, β= 102.555(0)°, V=0.2775(2) nm^3 and space group Pc(7). Ac impedance measurements in various atmospheres further support that it is an oxide ion conductor. This material was stable in various atmospheres with oxygen partial pressure p(O2) ranging from 1.0× 10^5 to 1.0× 10^-7 Pa at 800 ℃. A reversible polymorphic phase transition occurred at elevated temperatures as confirmed by the differential thermal analysis and dilatometric measurement.展开更多
LaMoNbOthick films have been successfully prepared by using a tape casting technique. Partial stabilization of the high temperature cubic phase is revealed in Nb doped LaMoO(LMO) films. The sintering temperature is de...LaMoNbOthick films have been successfully prepared by using a tape casting technique. Partial stabilization of the high temperature cubic phase is revealed in Nb doped LaMoO(LMO) films. The sintering temperature is decreased to 925 ℃ as compared with that of 1150 ℃ in bulk ceramics. The grain exhibits an oxide ionic conductivity of 0.014 S cmat 603 ℃ for LaMoNbO, which is 39% higher than pure LMO. Additionally, the Nb doped LMO films present low grain boundary resistance showing the potential application as solid electrolytes.展开更多
The structure, phase composition, and migration of oxygen ion in Ce3 NbO7+δ were reported on the basis of lone-pair substitution concept. X-ray diffraction study revealed that Ce3 NbO7+δ sample was comprised of Ce...The structure, phase composition, and migration of oxygen ion in Ce3 NbO7+δ were reported on the basis of lone-pair substitution concept. X-ray diffraction study revealed that Ce3 NbO7+δ sample was comprised of Ce3 NbO7+δ phase and CeNbO4.25 phase. In the dielectric study of Ce3 NbO7+δ sample, two dielectric loss peaks were observed both in temperature spectra and frequency spectra. Both peaks were shifted towards higher temperature with increase in frequency in temperature spectra and towards higher frequency with increase in temperature in frequency spectra, indicating the relaxation essence of these two peaks. It was suggested that the short distance diffusions of oxygen ions in both Ce3 NbO7+δ phase and CeNbO4.25 phase gave rise to the two dielectric relaxation peaks.展开更多
Off-stoichiometry of perovskite structural Bi0.5Na0.5TiO3(BNT)ferroelectrics can give rise to considerable oxide-ion conductivity.The inherent structural characteristics are urgent to be resolved due to its particular...Off-stoichiometry of perovskite structural Bi0.5Na0.5TiO3(BNT)ferroelectrics can give rise to considerable oxide-ion conductivity.The inherent structural characteristics are urgent to be resolved due to its particular sensitivity of the conduction mechanism to the nominal composition and synthesis process.Herein,a thorough study of the temperature-dependent neutron,X-ray diffraction and Raman spectrum is carried out on a series of equivalently substituted A-site deficient non-stoichiometric and pristine BNT.Phase transition and defect association are systemically investigated in these dominated rhombohedral phases at room temperature,associated with well saturated ferroelectric states.Significant structural evolution identified by Rietveld refinements and the origin of the electrical performance are clarified at elevated temperatures,focusing on the subtle distortions of ionic displacements,oxygen octahedral tilts and local chemical environments for oxygen vacancies.The ion migration ability mediated by oxygen vacancies that are not energetically favorable in BNT mainly depends on the external substitutional disorder,and is strongly affected by the dopant concentration.Together with the lone pair substitution concept,superior oxide ionic conductivity is achieved,and an alternative strategy is provided in designing BNT based oxide ion conductors.展开更多
文摘A series of compounds La2Mo2-xSnxO9-6 (x=0-0.3) have been synthesized by solid-state reaction technique. Materials have been characterized by XRD, SEM, DSC and impedance study. In the temperature regime 520℃-590 ℃, the specimens with x〈0.05 have the conductivity higher than La2Mo2O9. Conductivity of Sn-doped compound decreases consistently with increasing Sn-doping, compared to the undoped compound both below and above phase transition, barring the specimens with x〈 0.05, where conductivity values remains almost same as that of undoped specimen in high temperature region. In the intermediate temperature regime (520℃-590℃), the conductivity of doped compounds increases for x〈0.05 as compared to parent compound. Also, there is no indication of phase stabilization with Sn-doping in this compound even with the highest doping level, x=0.3. Electric modulus analysis suggests that thermally activated oxygen ion hopping mechanism is responsible for the conduction in Sn-doped compound.
基金the National Natural Science Foundation of China(Grant No.50672100)the Anhui Provincial Natural Science Foundation,China(Grant No.050440901)the Ningbo Civic Natural Science Foundation,China(Grant No.2006A610057).
文摘A cost-efFective technique, including nanocrystalline powder preparation using a modified Pechini method and a two-step low-temperature sintering route, was developed for the synthesis of high performance La2Mo2O9- based oxide-ion conductors. The optimum parameters of the compaction pressure, the first step and 'the second step sintering temperatures for the synthesis of fine grained, high density and uniform La2Mo2O9- based oxide-ion conductors were determined by a series of sintering experiments. High density and uniform sintered La2Mo2O9 samples with average grain size from 0.8 to 5 μm and La1.96K0.04Mo2O8.96 sample with average grain size as small as 500 nm were synthesized by using this cost-efFective method. The impedance measurement results show that the as-fabricated La2Mo2O9-based ceramics possess much higher ionic conductivity than that obtained by solid state reaction method. It is found that in the range of 0.8-5μm the grain size of dense La2Mo2O9 samples prepared from the nanocrystalline powders has little influence on their conductivities.
基金Project supported by the National Natural Science Foundation of China(Nos. 20331030, 20471058).
文摘A new oxide ion conductor, La3GaMo2O12, with a bulk conductivity of 2.7× 10^- 2 S·cm ^-1 at 800 ℃ in air atmosphere was prepared by the traditional solid-state reaction. The room temperature X-ray diffraction data could be indexed on a monoclinic cell with lattice parameters of a=0.5602(2) nm, b=0.3224(1) nm, c= 1.5741(1) nm, β= 102.555(0)°, V=0.2775(2) nm^3 and space group Pc(7). Ac impedance measurements in various atmospheres further support that it is an oxide ion conductor. This material was stable in various atmospheres with oxygen partial pressure p(O2) ranging from 1.0× 10^5 to 1.0× 10^-7 Pa at 800 ℃. A reversible polymorphic phase transition occurred at elevated temperatures as confirmed by the differential thermal analysis and dilatometric measurement.
基金supported by the National Natural Science Foundation(51602252,51372197)the Key Innovation Team of Shaanxi Province(2014KCT-04)+1 种基金the Major International Joint Research Program of Shaanxi Province(2012KW-10)the Outstanding Youth Science Fund of Xi’an University of Science and Technology
文摘LaMoNbOthick films have been successfully prepared by using a tape casting technique. Partial stabilization of the high temperature cubic phase is revealed in Nb doped LaMoO(LMO) films. The sintering temperature is decreased to 925 ℃ as compared with that of 1150 ℃ in bulk ceramics. The grain exhibits an oxide ionic conductivity of 0.014 S cmat 603 ℃ for LaMoNbO, which is 39% higher than pure LMO. Additionally, the Nb doped LMO films present low grain boundary resistance showing the potential application as solid electrolytes.
基金Project supported by the National Natural Science Foundation of China (50202012, 50672100)Natural Science of JiangxiProvince (0550090)
文摘The structure, phase composition, and migration of oxygen ion in Ce3 NbO7+δ were reported on the basis of lone-pair substitution concept. X-ray diffraction study revealed that Ce3 NbO7+δ sample was comprised of Ce3 NbO7+δ phase and CeNbO4.25 phase. In the dielectric study of Ce3 NbO7+δ sample, two dielectric loss peaks were observed both in temperature spectra and frequency spectra. Both peaks were shifted towards higher temperature with increase in frequency in temperature spectra and towards higher frequency with increase in temperature in frequency spectra, indicating the relaxation essence of these two peaks. It was suggested that the short distance diffusions of oxygen ions in both Ce3 NbO7+δ phase and CeNbO4.25 phase gave rise to the two dielectric relaxation peaks.
基金This work was supported by the National Natural Science Foundation(51702249,51602252,51761135118,U1732117)the China Postdoctoral Science Foundation(2017M613065)+2 种基金the Shaanxi Province Science Foundation(2020JQ-751)the Outstanding Youth Science Fund of XUST(2018YQ2-11)The authors thank Shiyanjia Lab for the XPS measurement.
文摘Off-stoichiometry of perovskite structural Bi0.5Na0.5TiO3(BNT)ferroelectrics can give rise to considerable oxide-ion conductivity.The inherent structural characteristics are urgent to be resolved due to its particular sensitivity of the conduction mechanism to the nominal composition and synthesis process.Herein,a thorough study of the temperature-dependent neutron,X-ray diffraction and Raman spectrum is carried out on a series of equivalently substituted A-site deficient non-stoichiometric and pristine BNT.Phase transition and defect association are systemically investigated in these dominated rhombohedral phases at room temperature,associated with well saturated ferroelectric states.Significant structural evolution identified by Rietveld refinements and the origin of the electrical performance are clarified at elevated temperatures,focusing on the subtle distortions of ionic displacements,oxygen octahedral tilts and local chemical environments for oxygen vacancies.The ion migration ability mediated by oxygen vacancies that are not energetically favorable in BNT mainly depends on the external substitutional disorder,and is strongly affected by the dopant concentration.Together with the lone pair substitution concept,superior oxide ionic conductivity is achieved,and an alternative strategy is provided in designing BNT based oxide ion conductors.