Optical, morphological, physical and crystalline properties of type structures CexAl2-xO3 (x = 0; 0.25; 0.50; 0.75 and 1) obtained by microwave assisted combustion

Abstract

Cerium aluminate is a perovskite type that presents AmBnO3 that has interesting physical, morphological properties and crystalline structures; however it has not been deeply studied when synthesized by microwave-assisted self-combustion specifically. Thus, the objective of this work was to synthesize CeAlO3 by microwave-assisted combustion method in an one-step using only one fuel (urea, 250% excess). Formulations were identified by CexAl2-xO3 (x = 0, 0.25, 0.50, 0.75 and 1; in mol), an α-Al2O3–standard was used how reference. X-ray diffraction (XRD), scanning electron microscopy (SEM-EDS and SEM-FEG), specific gravity, absorption spectroscopy in the ultraviolet and visible region (diffuse reflection), Fourier transform infrared spectroscopy (FTIR) and Raman were the techniques used in the characterizations. The results show that CeAlO3 was formed in the synthesis, as well as CeAl11O18 and CeO2 phase. In the diffuse reflection of light, the beginning of the increase in reflectivity occurs at wavelengths close to 380 nm and band-gap between 3.36 to 3.47 eV; the presence of microstructural and macrostructural defects impacted on the variation of reflectivity in the UV–visible region and on the variation of densities (5.06–5.96 g.cm−³); heterogeneous morphologies expressed by diversified surfaces, particulates tending to equiaxial symmetry and perforation signals, in addition to prismatic crystals growing parallel to the surface. The FTIR confirms the formations of α-Al2O3 and Raman confirms the presence of residual carbon. These results are relevant, since the work produced perovskites with stable structures in a single step, optimizing the manufacturing process of these materials with the elimination of calcination after synthesis.