Efeito da variação de pH na síntese e nas propriedades de BaCe0,2Pr0,8O3 obtido pelo método de complexação EDTA-citrato

Abstract

Barium cerate (BaCeO3) is a type ABO3 perovskite, with A and B metal cations. Such materials, single or doped, have been studied as promising for the application in solid oxide fuel cell, and hydrogen and oxygen permeation; however, as these materials have been produced by different synthesis methods, some conditions directly influence the final properties, with a major doping site B, which may have direct influence on the crystallite size and, consequently, in the ionic and electronic conduction. This work aimed at the partial substitution of cerium for 80% praseodymium by the EDTA-citrate complexing method to verify the influence of the pH of the synthesis solution on obtaining the phase, the crystallographic and morphological properties. It was found that the material has orthorhombic crystal structure with space group Pmcn and the phase was obtained irrespective of change of the pH of the synthesis, indicating possibly that the metal cations in the perovskite were able to deprotonate the EDTA increasing the stability of the complexes formed. With the synthesis pH adjusted to 5 the crystallite size reached the highest value, 352.7 nm. This increase was probably due to insufficient time in which the sample was subjected to the action of synthesis temperature until the formation of the final gel, resulting in reduced breakdown of agglomerates formed in the complexation reaction , which can be seen in the results of scanning electron microscopy