Papers by Keyword: CGO

Abstract: Solution Spray Pyrolysis (SST) was successfully implemented to fabricate thin perovskite and fluorite films on dense Yttria Stabilized Zirconia (YSZ) and Lanthanum Strontium Ferrate (LSF70) substrates. These composite structures are ubiquitous in solid oxide fuel cells and electrolyzers, CO gas sensors and ceramic membranes. With this technique, successful in situ manipulation of the film’s functional characteristics such as porosity and thickness is easily achieved by adjusting its functional parameters.In the present contribution, we report on the optimization of the physicochemical parameters of this open atmosphere technique with respect to the substrate temperature and deposition time for the fabrication of films of suitable morphology. Sintered films were characterized by XRD and SEM while thermal analysis was performed on the precursor salts. In addition, AC Impedance analysis was performed on some CGO films in order to assess their electron blocking capability in contact with the LSF substrates.

Abstract: The relationship between the microstructure and the conductivity of nanocrystallized oxygen ionic electrolytes has been received great interest since it provides guidelines for designing electrolytes with high performances which might find applications in fuel cells and oxygen sensors. Here, we present a strategy for controlling the calcination temperature to tune the crystallite size and ionic transport properties of solid electrolyte. Different crystallite sizes of Ce_0.8Gd_0.2O_2-δ (CGO) nanofiber electrolytes were prepared. As the average crystallite size decreased from 27 nm to 8 nm, the conductivity of the nanofibers increased by more than five times. An exceptionally high oxide ion conductivity of 0.023 S∙cm^-1 for the nanofibers was observed at 550°C. These insights into the effect of the crystallite size on the structure and the conductivity allow a better control of the electrical properties of solid electrolytes, which might foster their applications in electrochemical devices operable at lower temperatures.

Abstract: Depletion of fossil fuel at an alarming rate is a major concern of humankind. Consequently, researchers all over the world are putting a concerted effort for finding alternative and renewable energy. Solid oxide fuel cell (SOFC) is one such system. SOFCs are electrochemical devices that have several advantages over conventional power generation systems like high efficiency of power generation, low emission of green house gases and the fuel flexibility. The major research focus of recent times is to reduce the operating temperature of SOFC in the range of 500 to 700 °C so as to render it commercially viable. This reduction in temperature is largely dependent on finding an electrolyte material with adequate oxygen ion conductivity at the intended operating temperature. One much material is Gadolinia doped Ceria (CGO) that shows very good oxygen ion conductivity at the intended operation temperature. The aim of this overview is to highlight the contribution that materials chemistry has made to the development of CGO as an electrolyte.

Abstract: Nickel coated gadolinium doped ceria (GDC) powder was synthesized by microwave radiation and combustion. For the synthesis, the precipitates of gadolinium cerium oxycarbonate hydrate (GdxCe2-xO(CO3)2·H2O) were formed by a microwave radiated reaction between cerium nitrate (Ce(NO3)3.6H2O) and gadolinium nitrate (Gd(NO3)3.6H2O) and urea (CO(NH2)2), then nickel coatings on the gadolinium cerium oxycarbonate hydrate were performed by further microwave reaction between nickel chloride and urea. The shape and size of the gadolinium cerium oxycarbonate hydrate particles were critically dependent on aging time during microwave radiation. The irregular particles were transformed to rod shape particles with well-crystallized with increasing aging time to 40 min at 70 - 80°C because of the gradual decomposition of urea during microwave radiation. Small nickel precursor particles were homogeneously coated on the gadolinium cerium oxycarbonate hydrate particles with rod shape with aid of microwave radiation at 80 °C for 40 min. As a result, the nickel coated GDC nanopowders were sucessfully produced by the microwave radiation synthesis and further microwave combusted at 450°C for 20 min.

Abstract: Micro-tube type Gd-doped CeO2(CGO) reactor were prepared by hydrolysis of metal acetate gel at room temperature. The size of anode tube was ca. 0.8mm in diameter, and length was 20mm after sintering at 1400°C. DC conductivity of the prepared dense CGO cell consisting of 500nm grains was about 10 Ohm-cm at 600°C. Electrical power density of the micro-tube fuel cell, which was coated both CGO electrolyte and CGO/La0.6Sr0.4Co0.2Fe0.8O3 cathode on the surface of 40vol%NiO-CGO anode tube, was about 900mW/cm2 at 600°C under 30ml/min H2 gas flowing.