Preparation And Electrochemical Properties Of Gadolinium Doped Ceria Oxide Electrolyte Materials

Solid oxide fuel cell (SOFC) is a kind of efficient and environmentally friendlysolid-state power generation device. Since Y2O3stabilized ZrO2(YSZ) electrolytematerials operating temperature (1000℃) is too high, raising the cost of materials andreduce the stability of the battery. Thus, the development of intermediate temperaturesolid oxide electrolyte materials for solid oxide fuel cells becomes a research hotspot.Currently, intermediate temperature solid oxide electrolyte materials mainly are dopedCeO2material base, lanthanum gallate and so on. Doped CeO2-based materials chemicalratio simple, preparation process simple, but it also has its drawbacks, namely CeO2material sintering temperature is too high. High sintering temperature leads to the rapidgrowth of electrolyte materials grain sizes, and this will reduce the mechanicalproperties of the material. Therefore, how to reduce the sintering temperature of thematerial to improve the powder sintering activity and to produce a lower sinteringtemperature, high density, good electrical conductivity, good stability electrolytematerial is the focus of this paper.This paper selects Ce0.8Gd0.2O1.9(GDC) as the solid electrolyte materials, and Istart to study this material in two ways:(1) Incorporated the metal oxides as the sinteringaids;(2) Improved coprecipitation processes to prepare nano size particles, such canimprove the powders sintering activity. As a result, GDC electrolyte material whichincorporated into lithium oxide sintered at1250℃for20h has a higher density(>95%), and this is greatly reducing the sintering temperatures of the GDC electrolytematerial. GDC powders prepared by co-precipitation method which used ammoniumhydrogen carbonate as precipitant is nano-sized particles and have good sinteringactivity.With concentration of cerium and gadolinium nitrate solutions is0.15M, and theconcentration of ammonium hydrogen carbonate is0.75M, in which situation formedthe GDC electrolyte, and the relative density after sintering reached97%. GDC powderis prepared by oxalic acid as precipitant, and the particle size is micrometer. To discuss the stability of the electrolyte, a constant current was carried out to the electrolyte. AndAC impedance tests were performed before and after the constant current polarization.Calculated and compared the conductivity and activation energy values before and afterpolarization according to the impedance values. Experimental results show that theconductivity of the electrolyte is reduced after the polarization, and the activationenergy increased. Seen from the microstructure of the electrolyte sheets, the electrolytegrain boundaries between the grains become manifest after the constant polarization,and this lead to grain boundaries resistance increase, and the mass transport disruption.