Percorrer por autor "Cavaleiro, A."
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- Lanthanum silicate thin films for SOFC electrolytes synthesized by magnetron sputtering and subsequent annealingPublication . M.M. Vieira; Oliveira, J.C.; Shaula, A.L.; Cavaleiro, A.; Trindade, B.Thin films of La and Si with Si/(La+Si) atomic ratios ranging from 0.36 to 0.44 were produced by magnetron sputtering in pure Ar. For all compositions, the apatite-like La 9.33Si 6O 26 phase was formed during annealing in air at 900°C. A preferential orientation was developed during annealing of the films with higher silicon content while formation of oxide impurities was detected for the films with less silicon. Silicon segregation to the thin film/substrate interface was observed after annealing for thin films with higher Si/(La+Si) atomic ratios. The higher ionic conductivity values were obtained with the films with lower silicon content (2.81×10 -3Scm -1 at 800°C for the film with Si/(La+Si) atomic ratio of 0.36). This film presented the lower activation energy E a (0.94eV)
- Structure and ionic conductivity of reactively sputtered apatite-type lanthanum silicate thin filmsPublication . M.M. Vieira; Oliveira, J. C.; Shaula, A. L.; Trindade, B.; Cavaleiro, A.La–Si–O thin films with Si/(La + Si) atomic ratios ranging from 0.36 to 0.43 were produced by magnetron sputtering in a reactive Ar/O discharge gas. The as-deposited films have large X-ray diffraction peak characteristic of quasi-amorphousmaterials and oxygen contents from29 to 35 at.%. The Apatite-type lanthanumsilicate phase was formed in all the as-deposited films upon annealing at 900 °C for 1 h. The lanthanumsilicate films obtained by annealing the as-deposited filmswith lower Si/(La+Si) atomic ratios have a preferential orientationwith the c-axis perpendicular to the substrate while low intensity diffraction peaks ascribed to La2Si2O7 phase were detected in the films deposited with higher Si content. The preferentially oriented films have higher activation energy and lower ionic conductivity as the ionic conductivity measurements were performed in the direction perpendicular to the c-axis. The highest ionic conductivity was obtained for the film deposited with a Si/(La + Si) atomic ratio of 0.42, with a value of 1.2 × 10−2 S·cm−1 at 750 °C.