Hydrothermal synthesis and properties of ceria-based solid solutions as solid electrolytes for potential solid oxide fuel cell applications low-dimensional materials.

摘要

The structure, thermal expansion coefficients and ionic and electronic conductivities of Ce1-xBixO2-delta (x=0-0.30) solid solutions prepared hydrothermally were investigated. The uniformly small particle size (25-50 nm) of the hydrothermally prepared materials allows sintering of the samples into highly dense ceramic pellets at 900-1300°C, a significantly lower temperature, compared to that at 1600-1650°C required for ceria solid electrolytes prepared by solid state techniques. The solubility limit of Bi2O3 in CeO2 was determined to be around 20 mol.%. The maximum conductivity, sigma600°C ∼ 10 -2 S/cm with Ea=1.01 eV, was found at x=0.20. The structure, thermal expansion coefficients, ionic and electronic conductivities of Ce 1-xLa/NdxO2-delta (x=0-0.20 for La, and x=0-0.25 for Nd)) solid solutions, prepared for the first time hydrothermally, were investigated. The uniformly small particle size (25-50 nm) of the hydrothermally prepared materials allows sintering of the samples into highly dense ceramic pellets at 1300-1400°C, a significantly lower temperature, compared to that at 1600-1650°C required for ceria solid electrolytes prepared by solid state techniques. The maximum conductivity, sigma600°C ∼6.4x10 -3 S/cm with Ea=0.73 eV, was found at x=0.15 for La and sigma 600°C ∼9.0x10-3 S/cm with Ea=0.69 eV, was found at x=0.15 for Nd.; The structure, ionic and electronic conductivities of Ce1-xGd xO2-delta (x=0-0.30) solid solutions, prepared in a wide substitutional range for the first time hydrothermally, were investigated. The uniformly small particle size (41-68 nm) of the hydrothermally prepared materials allows sintering of the samples into highly dense ceramic pellets at 1300-1400 °C, a significantly lower temperature than 1600-1650 °C, which is required for ceria solid electrolytes prepared by solid state techniques. The maximum conductivity, sigma600°C ∼7.53x10 -3 S/cm with Ea=0.58 eV, was found at x=0.25.; The new reduced RP Ni (I) phase, La3Ni2O5.5 prepared by reduction of the Ni2.5+ containing La 3Ni2O6.93 using CaH2 as a reducing agent was studied by powder X-ray diffraction, thermogravimetric analysis, and magnetic susceptibility measurements. The same reduction process has been used for the reduction of LaSrNiO4, La1.5Sr0.5 NiO4, and La4Ni3O10. The structural and magnetic properties are discussed. The synthesis of novel oxide hydride compound is also briefly discussed.