The highly phase-pure electrolyte materials with composition La1.9Ba0.1Mo1.9Mn0.1O9(LBMMO) was prepared by the sol-gel auto-combustion method for intermediate-temperature solid oxide fuel cells(IT-SOFCs). The details of gel's auto-combustion, phase evolution, sintering, thermal expansion and electrochemical performance of LBMMO were investigated by means of thermo-gravimetry(TG), X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron spectroscopy(TEM), thermal expansion curve(TEC) and complex impedance spectra. The results showed that the highly phase-pure electrolyte LBMMO could be obtained after calcining at 600 °C. The sample sintered at 900 °C for 4 h in air exhibited a better sinterability, and the relative density of LBMMO was higher than 96%. The electrical conductivities of the sample were 6.7×10-3 and 25.9×10-3 S/cm at 700 and 800 °C in air, respectively. Results also showed that LBMMO had moderate thermal expansion(α=16.3×10-6 K-1, between room temperature and 800 °C) and an electrical activation energy equal to 1.32 eV).
Mn-Zn ferrites doped with different contents of Sm^(3+) and Gd^(3+) ions were prepared by sol-gel auto-combustion method and characterized by Fourier transform infrared spectroscopy(FTIR), thermogravimetric analysis(TG), X-ray diffraction(XRD), scanning electron microscopy(SEM) and vibrating sample magnetometer(VSM). When samples were calcined in a relatively low temperature below 1100 °C, secondary phases(α-Fe_2O_3) could be identified. Therefore, in order to acquire pure and better crystallinity, the suitable calcining temperature of powders was selected at 1200 °C. It was also found that all the samples consisting of ferrite phases of typical spinel cubic structure and average crystallite sizes between 31.5 and 38.2 nm were obtained after calcining at 1200 oC for 4 h. The lattice parameters increased almost linearly with increasing Sm content. A dense microstructure was obtained after sintering at 1250 °C for 4 h. Through the analysis of magnetic properties, hysteresis loops for all the samples were narrow with low values of coercivity and retentivity, indicating the paramagnetic nature of these samples. And saturation magnetization Ms strongly depended on the type of additive to reach a maximum of 47.99 emu/g for x=0.015, which showed a great promise for hyperthermia applications.
In this study, ultrafine Ce0.8La0.2–x Y x O1.9(for x=0, 0.05, 0.10, 0.15, 0.20) powders were successfully prepared by the sol-gel method.The samples were characterized by fourier transform infrared(FTIR), thermogravimetric and differential scanning calorimetry(TG-DSC), X-ray diffraction(XRD), scanning electron microscopy(SEM), AC impedance and thermal expansion measurements.Experimental results indicated that highly phase-pure cubic fluorite electrolyte Ce0.8La0.2–x Y x O1.9 powders were obtained after calcining at 600 °C.The as-synthesized powders exhibited high sintering activity, the Ce0.8La0.2–x Y x O1.9 series electrolytes which have higher relative densities over 96% could be obtained after sintered at 1400 °C for 4 h.Ce0.8La0.15Y0.05O1.9 electrolyte sintered at 1400 °C for 4 h exhibited higher oxide ionic conductivity(σ800 oC=0.057 S/cm), lower electrical activation energy(E a=0.87 e V) and moderate thermal expansion coefficient(TEC=15.5×10-6 K-1, temperature range 25–800 °C).
