Development of Ni-doped Yttria stabilized Zirconia composite for SOFC applications as Anodic material

Ni-doped Yttria stabilized Zirconia (NiO/YSZ) has been synthesized using low cost combustion process from an aqueous solution containing ZrO(NO3)2.6H2O, Y(NO3)3.6H2O, Ni(NO3)2.6H2O and urea. Pellets were sintered at 1350 0 C for 5 hours and its sintered density is estimated to be of 95%. Sintered pellets were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) & X-ray photoelectron spectroscopy (XPS) techniques. From the XRD analysis, as grown powder of NiO/YSZ showed nano-crystalline behavior with homogeneous mixture of YSZ and NiO phases. However sintered powder showed μ-size dense grain growth. Temperature and frequency dependent dielectric properties are corroborated with the conduction mechanism. Both dielectric constant (K) and loss (tan δ) are increased sharply at high temperature region, which is expected to be the onset of dipolar relaxation phenomena due to the presence of oxygen vacancies. A mixed conductivity involving ionic conduction in the high temperature range and electronic conduction in the low temperature range was observed. The decrease in K and tan δ with increase in frequency at a given temperature suggests the dynamic interaction of oxygen vacancies & oxide ion pairs.