Preparation and Characterization of Perovskite Oxides by Polymerization-Combustion

Abstract

This paper describes the preparation of La 0.75 Sr 0.25 Cr 0.2 Fe 0.8 O 3 perovskite oxide, using a polymerization-combustion route, to obtain materials for potential applications like electrodes in solid oxide fuel cells (SOFC). For such purpose, initially the solid precursor was characterized by FT-IR spectroscopy and thermal analysis (TGA-DTA), showing the obtention of polymeric citrate precursors. The thermal analysis (TGA-DTA), X-ray diffraction (XRD) and scanning electronic microscopy (SEM), provides information about the formation of a perovskite phase, while the texture, relief and roughness found are characteristic of the method of synthesis used. The size of crystallites, calculated using the Scherrer calculator software and transmission electron microscopy (TEM), confirmed the presence of nanometric crystallites (< 41.0 nm), whereas the chemical composition and crystallographic structure, indicating a high correlation with respect to proposed system, which was confirmed by X-ray fluorescence (XRF), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). Finally the electrical characterization by impedance spectroscopy (IS), determined the capacitance and resistance of the system in order to provide information related to the concentration of charge carriers and the diffusion rate of ions in the material a high conductivity values, related to semiconductor behavior for potential applications.

The Effect of Citric Acid Concentration on the Properties of LaMnO3 as a Catalyst for Hydrocarbon Oxidation

“…For the calcined catalyst, a strong band at about 588 cm −1 appeared, corresponding to the stretching mode involving the internal motion of a change in length of the Mn-O-Mn or Mn-O bond, as reported in the literature [41]. The last band at 588 cm −1 and the small band at 849 cm −1 could also be associated with the binding of metal cations, such as La 3+ with OH groups and oxygen atoms, according to the literature [38,39]. Finally, two bands at 1380 and 1498 cm -1 were found after calcination, which are more difficult to assign.…”

“…Nevertheless, these two bands may be attributed, if compared to those of the dried gel (un-supported precursor materials), to the C-O or M-O stretching modes, which shifted to a low and high wavenumber, respectively. This could indicate that coordination of metal cations by oxygen atoms occurs after the calcination process [39,40].…”

“…The bands at 733, 828, 1032, and 1432 cm −1 are assigned to the NO 3 − anions [36,40]. The bands at 1400, 1595, and 1678 cm −1 are due to the carboxylic groups (COO − ) [36,38,39] and the bands at 903 and 1280 cm −1 as well as the abovementioned band at 1032 cm −1 could be associated with the C-O stretching mode produced by the drying process of the citric acid foams [39,40]. After calcination, the bands of NO 3 − anions and carboxylic groups disappeared and bands of the O-H reduced significantly in intensity (see Figure 4).…”

Effect of Pr on the electrical and chemical properties of cerium oxide prepared by combustion method

“…The pellets were polished using SiC‐2000 abrasive paper, to provide an adequate contact surface, ensuring the diameter of the pellet of 8.0 mm and a thickness of 2.9 mm. The pellet faces were coated using platinum ink (Engelhart Clal product: Ink Platinum 6082), which was deposited by thermal treatment for 1 hour at 800°C . All measurements were stabilized for 20 minutes and the data derived from this analysis were corrected by the global geometry of the pellets and the reference cell in accordance with Beltrán et al…”

Chemical obtaining of LiMO2and LiM2O4(M=Co, Mn) oxides, for cathodic applications in Li-ion batteries

“…The amount of each precursor in each system was adjusted according to the corresponding hydrolysis constants with the subsequent addition of a solution of citric acid 1.0mol·L -1 in a molar ratio 0.5:1, with respect to the total cation content as has been established elsewhere [8]. Each system remained at reflux for 2 hours, after which the resulting sol was heated at 120°C to evaporate the solvent and obtain the corresponding solid precursor, which were calcined at 850°C for 15 hours to guarantee the consolidation of crystalline phases.…”