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.

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.

Ba 0.5 Sr 0.5 Co x Fe 1-x-y Ni y O 3-δ (BSCFNi; x = 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 effect of Ni -doping on crystal structure, thermal expansion coefficient (TEC) and dc electrical conductivity. A cubic perovskite structure was observed in the X-ray diffraction (XRD) measurement. The TEC of BSCFNi obtained for 0 ≤ y ≤ 0.25, varies in the range of (12.38–18.81) × 10-6 K-1, 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 1-x O 3-δ (BSCF) was improved by Ni -doping. The compound with y = 0.20 and 0.25 demonstrated a conductivity of σ = 62.59 S-cm-1 and 72.64 S-cm-1 at 400°C and 77.01 S-cm-1 and 89.68 S-cm-1 at 500°C.

Nickel doped BSCF (Ba 0.5 Sr 0.5 Co 1-x Fe 0.6 Ni x O 3-δ (BSCFNi); x=0.05, 0.1, 0.15, and 0.2) cathode materials were synthesized using sol-gel citrate method for low temperature (300-500 o C) Solid Oxide Fuel Cell (SOFC) application.The nanopowders of BSCFNi were then calcinated at various temperatures in the range of 600-1000 o C. The nanopowders were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM) and differential scanning calorimeter (DSC).A cubic perovskite structure was observed in the X-ray diffraction measurements.The average crystallite size of the nanopowder obtained varies between 40-60 nm.DSC result, measured in the temperature range of 200-600 o C, shows no phase transition.Ionic conductivity of the BSCFNi for varying concentration of nickel was measured in the temperature range of 200 o C to 500 o C.An emphasis is made on the effect of Ni doping on these properties.

Nanocrystalline powders of Ba0.5Sr0.5CoxFe1-x-yNiyO3-δ (x=0.4; y=0.05. 0.1, 0.15 and 0.2) have been syn- thesized by sol-gel process. The gel precursors obtained was calcined at various temperatures and the phase evolution was studied by XRD analysis. From the result of X-ray diffraction (XRD) patterns, it is found that a well crystalline cubic per- ovskite Ba0.5Sr0.5CoxFe1-x-yNiyO3-δ (BSCFNi) was obtained by calcining the precursor at 1000 oC for 4 hrs. Morphological analysis of the samples was done by scanning electron microscope (SEM). TGA results showed the lattice oxygen loss of the product was about ~2 % in its original weight in the temperature range 40-900 oC. In addition, AC impedance data revealed the better electrochemical performance of BSCFNi measured in the frequency range of 0.1 Hz to 1 MHz in relation to their potential use as intermediate tempera- ture (700-800 oC) SOFC cathode. An emphasis is made on the effect of Ni doping on these properties.

: 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.