Papers by Author: Márcia Caldeira Brant

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Authors: Márcia Caldeira Brant, Felipe da Silva Possa, Fernando Soares Lameiras
Abstract: Powders of Ce0.8Gd0.2O1.9 were synthesized by co-precipitation and amorphous citrate routes and their compositions and structures were compared. Co-precipitation process was carried out at room temperature, while amorphous citrate synthesis was performed at 60-70 °C. The powders obtained were calcined at 700 °C for 1 h. X-ray diffraction analyses showed that a single fluorite structure was formed by both synthesis techniques. Pellets from these powders were prepared by compaction at 30 kN/cm2 and sintered at 1593 °C in air. WDS analysis confirmed the homogeneity of the pellets. The sintered pellets obtained by amorphous citrate and by coprecipitation routes showed relative densities over 97 % of the theoretical density. These results indicated that the citrate amorphous route is an interesting and simple technique to prepare gadolinium-doped ceria powders with high sinterability.
Authors: Márcia Caldeira Brant, Jarlys Arthuri Zani, Fernando Soares Lameiras
Abstract: La0.8Sr0.2MnO3±d (LSM) powders were prepared by a Pechini-type polymerizable complex process and by amorphous citrate technique. Both processes involve the complexation of the LSM cations from their nitrates or carbonates. The aim of this work is to determinate the differences between the powers obtained by these techniques. The powders synthesized by the Pechini-type process were calcined between 500 °C and 1100 °C. The powders prepared by amorphous citrate technique were calcined at 900 °C. No contamination of either of the powders was observed by X ray fluorescence analysis. X ray diffraction results showed that a perovskitetype structure phase was obtained. BET results showed that the specific surface areas of the powders prepared by the polymerizable complex process and the amorphous citrate route were 6.6 m2g-1 and 5.7 m2g-1, respectively.
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