The cathode is one of the most important components of solid oxide fuel cells (SOFCs). The reduction of oxygen at the cathode (traditional cathodes like LSM, LSGM, etc.) is the slow step in the cell reaction at intermediate temperature (600–800[Formula: see text]C) which is one of the key obstacles to the development of SOFCs. The mixed ionic and electronic conducting cathode (MIEC) like LSCF, BSCF, etc., has recently been proposed as a promising cathode material for SOFC due to the improvement of the kinetic of the cathode reaction. The MIEC materials provide not only the electrons for the reduction of oxygen, but also the ionic conduction required to ensure the transport of the formed oxygen ions and thereby improves the overall electrochemical performance of SOFC system. The characteristics of MIEC cathode materials and its comparison with other traditional cathode materials is studied and presented in the paper.
BSCFNi; x ¼ 0:4, 0 y 0:25) were studied in relation to their potential use as intermediate temperature solid oxide fuel cell (IT-SOFC) cathode. An emphasis is made on the e®ect of Ni-doping on crystal structure, thermal expansion coe±cient (TEC) and dc electrical conductivity. A cubic perovskite structure was observed in the X-ray di®raction (XRD) measurement. The TEC of BSCFNi obtained for 0 y 0:25, varies in the range of (12.38-18.81) Â10 À6 K À1 , measured in the temperature range of 30 C to 800 C. The electrical conductivity which is a major defect of Ba 0:5 Sr 0:5 Co x Fe 1Àx O 3À (BSCF) was improved by Ni-doping. The compound with y ¼ 0:20 and 0.25 demonstrated a conductivity of ¼ 62:59 S-cm À1 and 72.64 S-cm À1 at 400 C and 77.01 S-cm À1 and 89.68 S-cm À1 at 500 C.
The composite of (1-x) Ni 0.53 Cu 0.12 Zn 0.35 Fe 1.88 O 4 + (x) Gd 0.2 Ce 0.8 O 3 (x=0.10,0.20,0.30) were prepared by mixing nanocrystalline Ni 0.53 Cu 0.12 Zn 0.35 Fe 1.88 O 4 and Gd 0.2 Ce 0.8 O 3 powders at different weights percents. The powders of NiCuZn ferrite were synthesized using sol gel method. The powders were densified using conventional sintering method at 1000°C/2 hrs. The phase and morphology of the composites was observed with X-ray diffraction (XRD) and Scanning Electron Microscope (SEM). The frequency dependence of real (ε′) and imaginary (ε″) parts of permittivity was measured in the range of 1MHz-1.8GHz.
We present a comparative study of the variation in dielectric relaxation for the additives SiO2, TiO2 and ZrO2 in cobalt ferrite. CoFe2O4 was prepared using microwave hydrothermal system and sintered at 900 °C/30 min
using microwave sintering method. Real and imaginary parts of permittivity were measured in the frequency range of 1 MHz to 1.8 GHz for these samples. A shift in the dielectric relaxation towards higher frequencies for doped samples is observed as expected in percolating systems.
A non-linear least square fit of the electron oscillator model is used to parameterize absorption in the samples.
Soft ferrite (Mn0.4Zn0.6Fe2O4) and hard ferrite (Co0.4Zn0.6Fe2O4) nanocomposites (x Mn0.4Zn0.6Fe2O4 + (1-x) Co0.4Zn0.6Fe2O4 (where x= 0.25, 0.5, 0.75) were prepared with different weight percent. Crystal structures and microstructures of these composites have been investigated by using X-ray diffraction and scanning electron microscope for composite samples sintered at 900°C/30 min using microwave sintering technique. The effect of composite weight percent on dielectric properties of composites are examined over a wide frequency range (1MHz-1.8GHz) by studying the real and imaginary part of permittivity with available theories. Investigation show variation of mixed ferrites for resistivity and resonating frequency.
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