(Digital Presentation) Study of Structural and Ionic Conductivity Property in Gd3+ and Sm3+ Co-Doped Ceria for Low Temperature SOFC Electrolyte Application

Abstract

In recent years, fuel cells have become one of the most efficient and clean energy conversion devices. Due to their use in stationary as well as mobile power applications, they have also gained a lot of attention in this field. From all other fuel cells, SOFC has several advantages such as absence of liquid component, vibration free working, fuel and many more. However, two most crucial aspects of SOFC are operating temperature and the choice of electrolyte materials. It is the most efficient fuel cell with a setback in its elevated operating temperature, as high as around 800℃ -1000℃. To achieve high ionic conductivity in a SOFC, it is very important to tailor the electrolyte properties, simultaneously reducing the operating temperature.Conventionally, Yttria Stabilized Zirconia (YSZ) has been the most studied electrolyte material with a limiting factor of its high operating temperature. Doped Ceria has been one of the most explored alternatives of YSZ, which not only reduces the operating temperature but also enhances the ionic efficiency due to its electro-catalytic property. The double valency property of CeO2 occurring due to oxygen non-stoichiometry (CeO2-δ), generates oxygen vacancies making it a potential electrolyte material. Rare Earth (RE) dopants like Gd3+ and Sm3+ have reported to have high ionic conductivity at low temperatures. In the present study, synthesis of Sm-Gd- co-doped CeO2 by wet chemical route to ensure homogenous distribution, with the stoichiometry Ce1-a Gda-y Smy O2-0.5δ where a=0.20 and 0≤y≤a. It was prepared by modified co-precipitation method wherein, no additional water has been utilized during the co-precipitation process in order to minimize the particle agglomeration. Phase pure particles were obtained by calcining the precipitants at 650℃ in air and the green body made from it were sintered in air at elevated temperature of 1450 °C to achieve high density pellet. XRD and Raman spectroscopy confirmed successful substitution of both dopants and presence of single-phase cubic structure of the nanoparticles. The surface morphology was studied using FESEM which showed highly dense structure with more than 97% density. The electrochemical impedance spectroscopy (EIS) of the sintered pellets in the temperature range of 400-700℃, showed much higher conductivity then singly doped Ceria . Figure 1