Determinação de algumas propriedades térmicas de cerâmicas avançadas dopadas com íon terra rara Ce4

Abstract

This work is based on the study some thermal properties of double perovskite ceramics 𝐴2𝐵𝐵′𝑂6, relating these properties with their microstructural characteristics. The results define key parameters on the durability at high temperatures, creep resistance and better understanding of the heat transport in porous media. The samples 𝐶𝑎2𝑀𝑛𝑅𝑒𝑂6 and 𝐶𝑎1,8𝐶𝑒0,2𝑀𝑛𝑅𝑒𝑂6 which were prepared using the technique of solid state reaction were studied here. It was described the procedure used by the research group for synthesizing the crystalline structure, which was verified by X-ray patterns analysis. The scanning electron microscope images allowed assessing the average size of grain junctions between. In order to evaluate this average particle size, it was carried out a statistical size measurement of the junctions between grains. Taking the histograms produced, it was fitted a curve of a statistical gamma distribution density range. Information about the atomic concentrations in the inner grain regions and the grain boundary were obtained by analyzing the spectra of Energy Dispersive Spectrometry (EDS). We observed that the undoped sample showed higher average size of junctions and a greater concentration of rhenium atoms in grain boundary unlike doped sample in which there were no major changes in the concentrations of the studied regions. We use the Laser Flash method to develop a study of the thermal diffusivity. This method has the advantage of simultaneous determination of important thermodynamic parameters in a very short time interval. A low value of thermal diffusivity around (0,27±0,09).10−7 (𝑚2/𝑠) was observed for undoped sample, unlike doped with cerium which showed 5-fold higher values. This difference was associated with high porosity observed in the sample 𝐶𝑎2𝑀𝑛𝑅𝑒𝑂6.