Combustion synthesis of nanocrystalline yttria-doped ceria

Abstract

Nanocrystalline yttria-doped ceria powder, with the composition Ce 0.55 Y 0.45 O 1.775 , was synthesized by a combustion technique using citric acid as the fuel and the corresponding metal nitrates as oxidants. This process involves mild conditions as the external temperature required to initiate the combustion is only approximately 250°C. The product was characterized by x-ray diffraction (XRD) to ascertain the phase purity. The crystallite size of these calcined samples, as seen by transmission electron microscopy, was found to be in the range 6 nm to 50 nm. The surface area of the fine powder, as obtained from the Brunauer-Emmett-Teller technique, was about 140 m 2 /g. The agglomeration behavior as a function of temperature and the lattice thermal expansion studies were carried out using high-temperature XRD. This nanocrystalline powder resulted in nearly theoretical bulk density at a relatively lower temperature, which is attributed to the superior powder properties. The sintered microstructure, as studied by scanning electron microscopy, revealed the presence of fine grains.

Nanoparticles and Nanoceramics of Y-doped CeO2

“…We used the combustion synthesis route to prepare the nanoparticles (15). Metallic nitrates were the oxydising agent and urea or glycine were used as the reducing compound.…”

“…For a long time, it was considered that dense samples could only be obtained with high temperature (>1500°C) treatments (14); this implies problems associated with the processing of the final product such as unwanted ECS Transactions, 2 (16) 1-10 (2007) 10.1149/1.2424305, copyright The Electrochemical Society cation diffusion between different components, expensive high temperature annealing, evaporation of materials, etc. However, the situation changed over the years and recent reports indicate that this can be done at lower temperatures <1300°C (15,16) when starting from nanopowders; furthermore, the low temperature treatments keep the grains small (13) therefore providing a tool for material tailoring. Our work deals as well with a suitable preparation method for dense materials with small grain size.…”

Low-temperature sintering of dense lanthanum silicate electrolytes with apatite-type structure using an organic precipitant synthesized nanopowder

“…[1][2][3] Until recently, conventionally used solid electrolytes with high ionic conductivity consisted of fluorite-structured stabilized zirconia, which requires an operating temperature above 900-1000 C. [4][5][6][7] Therefore, serious attention has been paid to finding alternative electrolytes for IT-SOFCs, which has led to the development of fluorite and perovskite structures, such as doped ceria and doped lanthanum gallate, respectively. 3,4,[8][9][10][11] However, the application of those materials has been limited by the increase in the electronic conductivity, which occurs in doped-ceria-based electrolytes and by the insufficient chemical stability that characterizes doped lanthanum gallate materials. 12 Lanthanum silicate-based compositions that have an apatite-type structure and high electric conductivity have recently attracted significant interest.…”

Nanoparticles and Nanograin-Sized Y-Doped CeO[sub 2] Ceramics

“…For a long time, the standard procedure to prepare dense samples involved high-temperature ͑Ͼ1500°C͒ treatments; 16 this introduces problems associated with the processing of the final product such as unwanted cation diffusion between different components, expensive high-temperature annealing, and evaporation of materials, among others. However, the situation changed over the years and recent reports indicate that this can be done at lower temperatures Ͻ1300°C 17,18 when starting from nanopowders; fur-thermore, the low-temperature treatments keep the grains small, 13 therefore providing a tool for the tailoring of material properties. Our work evaluates a preparation method of dense materials with small grain size.…”

“…A preliminary version of this article has been presented elsewhere. 19 Experimental Synthesis of nanoparticles.-We used the combustion synthesis route 17 to prepare nanoparticles of Ce 1−x Y x O 2−␦ ͑x = 0, 0.1, 0.2 0.3͒. Ce͑NO 3 ͒ 3 •6H 2 O ͑Aldrich, 99.9%͒ and Y͑NO 3 ͒ 3 •6H 2 O ͑Aldrich, 99.9%͒ were used as the oxidizing agents and urea ͑Farmacia Paris, 98%͒ or glycine ͑Aldrich, Ͼ99%͒ as the reducing compound.…”